Heterotrimeric G-proteins, consisting of Ga, Gb and Gg subunits, are important signal transducers... more Heterotrimeric G-proteins, consisting of Ga, Gb and Gg subunits, are important signal transducers in eukaryotes. In plants, G-protein-mediated signaling contributes to defense against a range of fungal and bacterial pathogens. Here we studied response of G-protein-deficient mutants to ssRNA viruses representing 2 different families: Cucumber mosaic virus (CMV) (Bromoviridae) and Turnip mosaic virus (TuMV) (Potyviridae). We found that development of spreading necrosis on infected plants was suppressed in the Gb-deficient mutant (agb1-2) compared to wild type and Ga-deficient mutant (gpa1-4). In accordance, ion leakage caused by viral infection was also significantly reduced in agb1-2 compared to wild type and gpa1-4. Nevertheless, both viruses replicated better in agb1-2 plants, while gpa1-4 was similar to wild type. Analysis of pathogenesis-related genes showed that Gb negatively regulated salicylic acid, jasmonic acid and abscisic acid marker genes during CMV and TuMV infections. Interestingly, analysis of salicylic acid deficient transgenic plants indicated that salicylic acid did not affect resistance against these viruses and did not influence the Gb-mediated defense response. We conclude that heterotrimeric G-proteins play a positive role in defense against viral pathogens probably by promoting cell death.
Climate change culminating in increased temperature, sea-level rise, flooding amidst strong winds... more Climate change culminating in increased temperature, sea-level rise, flooding amidst strong winds and heavy rainfall cause mechanical stress (MS) that affects the habitat of several plant species. In response, plants activate a plethora of molecular and physiological processes that alter their architecture causing a phenomenon referred to as thigmomorphogenesis. Plants develop thicker stem, smaller leaves, reduced height and overall increased in tensile strength. These alterations facilitate forest trees to survive windthrows and mitigate subsequent stress. Plants can desensitise their molecular response to repetitive MS, as an adaptive mechanism to prevent unwanted thigmomorphogenesis. Plants may want to ‘remember’ MS since it is natural ubiquitous stress stimuli that occur daily, be it from insect feeding, high winds, animal stamping or heavy rainfall. For more than a century, in Japan and China, stamping on crops, as a form of MS has been used to harden crops against extreme weat...
A single event of mechanical stimulation is perceived by mechanoreceptors that transduce rapid tr... more A single event of mechanical stimulation is perceived by mechanoreceptors that transduce rapid transient signalling to regulate gene expression. Prolonged mechanical stress for days to weeks culminates in cellular changes that strengthen the plant architecture leading to thigmomorphogenesis. The convergence of multiple signalling pathways regulates mechanically induced tolerance to numerous biotic and abiotic stresses. Emerging evidence showed prolonged mechanical stimulation can modify the baseline level of gene expression in naive tissues, heighten gene expression, and prime disease resistance upon a subsequent pathogen encounter. The phenotypes of thigmomorphogenesis can persist throughout growth without continued stimulation, revealing somatic‐stress memory. Epigenetic processes regulate TOUCH gene expression and could program transcriptional memory in differentiating cells to program thigmomorphogenesis. We discuss the early perception, gene regulatory and phytohormone pathways...
Carotenoids are secondary metabolites synthesized in plastids that function in photosynthesis, ph... more Carotenoids are secondary metabolites synthesized in plastids that function in photosynthesis, photoprotection, growth and development of plants. Carotenoids contribute to the yellowish, orange and pinkish-red hues of leaves, flowers and fruits, as well as various aromas. They provide substrates for the biosynthesis of phytohormones and are cleavable into smaller apocarotenoids that function as retrograde signals and/or mediate intracellular communication as well as regulate gene transcription and/or protein translation. Carotenoid biosynthesis and gene regulation are tightly coordinated with tissue-specific plastid differentiation, seedling morphogenesis, fruit development, and prevailing environmental growth conditions such as light, temperature and mycorrhizal interactions. In the last decade, epigenetic processes have been linked to the regulation of carotenoid biosynthesis, accumulation and degradation during plant development. Next-generation sequencing approaches have shed new light on key rate-limiting steps in carotenoid pathways targeted by epigenetic modifications that synchronize carotenoid accumulation with plastid development and morphogenesis. We discuss how histone modifications (methylation and acetylation), DNA methylation and demethylation, as well as small RNA gene silencing processes can modulate carotenoid biosynthesis, accumulation and apocarotenoid generation throughout the life cycle of plant from seed germination to fruit morphogenesis. This review highlights how apocarotenoid signals regulate plastid biogenesis and gene expression in sync with chromatin alterations during skoto-and photomorphogenesis. We provide a new perspective based upon emerging evidence that supports a likely role for carotenoids in contributing to the programming and/or maintenance of the plants' epigenetic landscape.
Twenty five accessions of okra collected in Ghana were evaluated for phenotypic identity, diversi... more Twenty five accessions of okra collected in Ghana were evaluated for phenotypic identity, diversity and quality based on morphological characters. Qualitative and quantitative characteristics were measured and scored as specified by the standard international crop descriptor for okra. A dendrogram was generated for morphological data based on the simple matching coefficient, and four cluster groups were observed. The distribution of the accessions into the groups, based on the morphological traits had no unique geographical relationship. The results of the matrix of similarity among the 25 accessions performed by NTsys pc programme placed two accessions in a tie, suggesting that, they were identical. Eight accessions were placed at above 80% similarity, meaning that, the accession pairs were closely related, and three accessions were 50% similar, which means they matched at half the characters measured. Six pairs of accessions measured were somewhat diverse, which can be exploited b...
Twenty-five accessions of okra collected from different parts of Ghana were evaluated for their h... more Twenty-five accessions of okra collected from different parts of Ghana were evaluated for their horticultural and agronomic attributes in the major and minor cropping seasons of 2008 at the crop and soil sciences experimental field, Kwame Nkrumah University of Science and Technology (KNUST) Kumasi, Ghana, using a randomized complete block design (RCBD) with four replications. The objectives of the experiment were to investigate the horticultural characteristics and performance of all the okra entries. Data collected included fruit and leaf characteristics; Days to first flowering, first flowering node, first fruit-producing node, fresh fruit weight, fruit length at maturity, fruit width, maximum plant height, number of internode, number of seeds per fruit, number of total fruits per plant, seed yield, 100 seed weight. The accessions KNUST/SL1/07Nkrumahene, DA/08/02Dikaba and GH 5787Asontem, GH6102Fetri and 'Asontem' showed number of days from sowing to first-flowering at between 44.00 and 48.00 days, first flowering and fruiting nodes at between 5.00 and 6.00th nodes, days to 50% emergence at 8 days after sowing, the average number to total fruits per plant at 60.00 to 145.00 fruits and green immature fruit colour. The results showed that most of the okra displayed symptoms of okra mosaic virus (OMV) and okra leaf curl virus (OLCV). Fruit size varied among the entries. A correlation of the characters with the total fruit production showed that plant height, days to flowering and nodulation, fruit yield and seed yield recorded positive and significant associations, which generally mean that they influenced fruit production or yield. Specific accessions; KNUST/SL1/07Nkrumahene, DA/08/02Dikaba and GH 5787Asontem, GH6102Fetri and 'Asontem', identified in this study, could be passed on to breeders for utilization in the okra improvement programmes in Ghana.
Enhancing crop yields is a major challenge because of an increasing human population, climate cha... more Enhancing crop yields is a major challenge because of an increasing human population, climate change, and reduction in arable land. Here, we demonstrate that long-lasting growth enhancement and increased stress tolerance occur by pretreatment of dark grown Arabidopsis seedlings with ethylene before transitioning into light. Plants treated this way had longer primary roots, more and longer lateral roots, and larger aerial tissue and were more tolerant to high temperature, salt, and recovery from hypoxia stress. We attributed the increase in plant growth and stress tolerance to ethylene-induced photosynthetic-derived sugars because ethylene pretreatment caused a 23% increase in carbon assimilation and increased the levels of glucose (266%), sucrose/trehalose (446%), and starch (87%). Metabolomic and transcriptomic analyses several days posttreatment showed a significant increase in metabolic processes and gene transcripts implicated in cell division, photosynthesis, and carbohydrate m...
Heterotrimeric G-proteins, consisting of Gα, Gβ and Gγ subunits, are important signal transducers... more Heterotrimeric G-proteins, consisting of Gα, Gβ and Gγ subunits, are important signal transducers in eukaryotes. In plants, G-protein-mediated signaling contributes to defense against a range of fungal and bacterial pathogens. Here we studied response of G-protein-deficient mutants to ssRNA viruses representing 2 different families: Cucumber mosaic virus (CMV) (Bromoviridae) and Turnip mosaic virus (TuMV) (Potyviridae). We found that development of spreading necrosis on infected plants was suppressed in the Gβ-deficient mutant (agb1-2) compared to wild type and Gα-deficient mutant (gpa1-4). In accordance, ion leakage caused by viral infection was also significantly reduced in agb1-2 compared to wild type and gpa1-4. Nevertheless, both viruses replicated better in agb1-2 plants, while gpa1-4 was similar to wild type. Analysis of pathogenesis-related genes showed that Gβ negatively regulated salicylic acid, jasmonic acid and abscisic acid marker genes during CMV and TuMV infections. I...
In animals, heterotrimeric G proteins, comprising Ga, Gb, and Gg subunits, are molecular switches... more In animals, heterotrimeric G proteins, comprising Ga, Gb, and Gg subunits, are molecular switches whose function tightly depends on Ga and Gbg interaction. Intriguingly, in Arabidopsis (Arabidopsis thaliana), multiple defense responses involve Gbg, but not Ga. We report here that the Gbg dimer directly partners with extra-large G proteins (XLGs) to mediate plant immunity. Arabidopsis mutants deficient in XLGs, Gb, and Gg are similarly compromised in several pathogen defense responses, including disease development and production of reactive oxygen species. Genetic analysis of double, triple, and quadruple mutants confirmed that XLGs and Gbg functionally interact in the same defense signaling pathways. In addition, mutations in XLG2 suppressed the seedling lethal and cell death phenotypes of BRASSINOSTEROID INSENSITIVE1-associated receptor kinase1-interacting receptor-like kinase1 mutants in an identical way as reported for Arabidopsis Gb-deficient mutants. Yeast (Saccharomyces cerevisiae) three-hybrid and bimolecular fluorescent complementation assays revealed that XLG2 physically interacts with all three possible Gbg dimers at the plasma membrane. Phylogenetic analysis indicated a close relationship between XLGs and plant Ga subunits, placing the divergence point at the dawn of land plant evolution. Based on these findings, we conclude that XLGs form functional complexes with Gbg dimers, although the mechanism of action of these complexes, including activation/deactivation, must be radically different form the one used by the canonical Ga subunit and are not likely to share the same receptors. Accordingly, XLGs expand the repertoire of heterotrimeric G proteins in plants and reveal a higher level of diversity in heterotrimeric G protein signaling.
BackgroundProlonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation respo... more BackgroundProlonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation response associated with increased disease resistance. What remains unclear is if; 1) plants pre-exposed to a short period of repetitive MS can prime defence responses upon subsequent challenge with necrotrophic pathogens, 2) MS mediates plant immunity via jasmonic acid (JA) signalling, and 3) a short period of repetitive MS can cause long-term changes in gene expression resembling a stress-induced memory. To address these points, 10-days old juvenileArabidopsisseedlings were mechanically stressed for 7-days using a soft brush and subsequently challenged with the necrotrophic pathogens,Alternaria brassicicola,andBotrytis cinerea. Here we assessed how MS impacted structural cell wall appositions, disease symptoms and altered gene expression in response to infection.ResultsThe MS-treated plants exhibited enhanced cell wall appositions and jasmonic acid (JA) accumulation that correlated with a r...
Heterotrimeric G-proteins, consisting of Ga, Gb and Gg subunits, are important signal transducers... more Heterotrimeric G-proteins, consisting of Ga, Gb and Gg subunits, are important signal transducers in eukaryotes. In plants, G-protein-mediated signaling contributes to defense against a range of fungal and bacterial pathogens. Here we studied response of G-protein-deficient mutants to ssRNA viruses representing 2 different families: Cucumber mosaic virus (CMV) (Bromoviridae) and Turnip mosaic virus (TuMV) (Potyviridae). We found that development of spreading necrosis on infected plants was suppressed in the Gb-deficient mutant (agb1-2) compared to wild type and Ga-deficient mutant (gpa1-4). In accordance, ion leakage caused by viral infection was also significantly reduced in agb1-2 compared to wild type and gpa1-4. Nevertheless, both viruses replicated better in agb1-2 plants, while gpa1-4 was similar to wild type. Analysis of pathogenesis-related genes showed that Gb negatively regulated salicylic acid, jasmonic acid and abscisic acid marker genes during CMV and TuMV infections. Interestingly, analysis of salicylic acid deficient transgenic plants indicated that salicylic acid did not affect resistance against these viruses and did not influence the Gb-mediated defense response. We conclude that heterotrimeric G-proteins play a positive role in defense against viral pathogens probably by promoting cell death.
Background: Prolonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation res... more Background: Prolonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation response associated with increased disease resistance. What remains unclear is if; 1) plants pre-exposed to a short period of repetitive MS can prime defence responses upon subsequent challenge with necrotrophic pathogens, 2) MS mediates plant immunity via jasmonic acid (JA) signalling, and 3) a short period of repetitive MS can cause longterm changes in gene expression resembling a stress-induced memory. To address these points, 10-days old juvenile Arabidopsis seedlings were mechanically stressed for 7-days using a soft brush and subsequently challenged with the necrotrophic pathogens, Alternaria brassicicola, and Botrytis cinerea. Here we assessed how MS impacted structural cell wall appositions, disease symptoms and altered gene expression in response to infection. Results: The MS-treated plants exhibited enhanced cell wall appositions and jasmonic acid (JA) accumulation that correlated with a reduction in disease progression compared to unstressed plants. The expression of genes involved in JA signalling, callose deposition, peroxidase and phytoalexin biosynthesis and reactive oxygen species detoxification were hyper-induced 4-days post-infection in MS-treated plants. The loss-of-function in JA signalling mediated by the JA-insensitive coronatine-insensitive 1 (coi1) mutant impaired the hyper-induction of defense gene expression and promoted pathogen proliferation in MS-treated plants subject to infection. The basal expression level of PATHOGENESIS-RELATED GENE 1 and PLANT DEFENSIN 1.2 defense marker genes were constitutively upregulated in rosette leaves for 5-days post-MS, as well as in naïve cauline leaves that differentiated from the inflorescence meristem well after ceasing MS. Conclusion: This study reveals that exposure of juvenile Arabidopsis plants to a short repetitive period of MS can alter gene expression and prime plant resistance upon subsequent challenge with necrotrophic pathogens via the JA-mediated COI1 signalling pathway. MS may facilitate a stress-induced memory to modulate the plant's response to future stress encounters. These data advance our understanding of how MS primes plant immunity against necrotrophic pathogens and how that could be utilised in sustainable agricultural practices.
Background: Prolonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation res... more Background: Prolonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation response associated with increased disease resistance. What remains unclear is if; 1) plants pre-exposed to a short period of repetitive MS can prime defence responses upon subsequent challenge with necrotrophic pathogens, 2) MS mediates plant immunity via jasmonic acid (JA) signalling, and 3) a short period of repetitive MS can cause longterm changes in gene expression resembling a stress-induced memory. To address these points, 10-days old juvenile Arabidopsis seedlings were mechanically stressed for 7-days using a soft brush and subsequently challenged with the necrotrophic pathogens, Alternaria brassicicola, and Botrytis cinerea. Here we assessed how MS impacted structural cell wall appositions, disease symptoms and altered gene expression in response to infection. Results: The MS-treated plants exhibited enhanced cell wall appositions and jasmonic acid (JA) accumulation that correlated with a reduction in disease progression compared to unstressed plants. The expression of genes involved in JA signalling, callose deposition, peroxidase and phytoalexin biosynthesis and reactive oxygen species detoxification were hyper-induced 4-days post-infection in MS-treated plants. The loss-of-function in JA signalling mediated by the JA-insensitive coronatine-insensitive 1 (coi1) mutant impaired the hyper-induction of defense gene expression and promoted pathogen proliferation in MS-treated plants subject to infection. The basal expression level of PATHOGENESIS-RELATED GENE 1 and PLANT DEFENSIN 1.2 defense marker genes were constitutively upregulated in rosette leaves for 5-days post-MS, as well as in naïve cauline leaves that differentiated from the inflorescence meristem well after ceasing MS. Conclusion: This study reveals that exposure of juvenile Arabidopsis plants to a short repetitive period of MS can alter gene expression and prime plant resistance upon subsequent challenge with necrotrophic pathogens via the JA-mediated COI1 signalling pathway. MS may facilitate a stress-induced memory to modulate the plant's response to future stress encounters. These data advance our understanding of how MS primes plant immunity against necrotrophic pathogens and how that could be utilised in sustainable agricultural practices.
Enhancing crop yields is a major challenge because of an increasing human population, climate cha... more Enhancing crop yields is a major challenge because of an increasing human population, climate change, and reduction in arable land. Here, we demonstrate that long-lasting growth enhancement and increased stress tolerance occur by pretreatment of dark grown Arabidopsis seedlings with ethylene before transitioning into light. Plants treated this way had longer primary roots, more and longer lateral roots, and larger aerial tissue and were more tolerant to high temperature, salt, and recovery from hypoxia stress. We attributed the increase in plant growth and stress tolerance to ethylene-induced photosynthetic-derived sugars because ethylene pretreatment caused a 23% increase in carbon assimilation and increased the levels of glucose (266%), sucrose/trehalose (446%), and starch (87%). Metabolomic and transcriptomic analyses several days posttreatment showed a significant increase in metabolic processes and gene transcripts implicated in cell division, photosynthesis, and carbohydrate metabolism. Because of this large effect on metabolism, we term this “ethylene-mediated metabolic priming.” Reducing photosynthesis with inhibitors or mutants prevented the growth enhancement, but this was partially rescued by exogenous sucrose, implicating sugars in this growth phenomenon. Additionally, ethylene pretreatment increased the levels of CINV1 and CINV2 encoding invertases that hydrolyze sucrose, and cinv1; cinv2 mutants did not respond to ethylene pretreatment with increased growth indicating increased sucrose breakdown is critical for this trait. A model is proposed where ethylene-mediated metabolic priming causes long-term increases in photosynthesis and carbohydrate utilization to increase growth. These responses may be part of the natural development of seedlings as they navigate through the soil to emerge into light.
Heterotrimeric G-proteins, consisting of Ga, Gb and Gg subunits, are important signal transducers... more Heterotrimeric G-proteins, consisting of Ga, Gb and Gg subunits, are important signal transducers in eukaryotes. In plants, G-protein-mediated signaling contributes to defense against a range of fungal and bacterial pathogens. Here we studied response of G-protein-deficient mutants to ssRNA viruses representing 2 different families: Cucumber mosaic virus (CMV) (Bromoviridae) and Turnip mosaic virus (TuMV) (Potyviridae). We found that development of spreading necrosis on infected plants was suppressed in the Gb-deficient mutant (agb1-2) compared to wild type and Ga-deficient mutant (gpa1-4). In accordance, ion leakage caused by viral infection was also significantly reduced in agb1-2 compared to wild type and gpa1-4. Nevertheless, both viruses replicated better in agb1-2 plants, while gpa1-4 was similar to wild type. Analysis of pathogenesis-related genes showed that Gb negatively regulated salicylic acid, jasmonic acid and abscisic acid marker genes during CMV and TuMV infections. Interestingly, analysis of salicylic acid deficient transgenic plants indicated that salicylic acid did not affect resistance against these viruses and did not influence the Gb-mediated defense response. We conclude that heterotrimeric G-proteins play a positive role in defense against viral pathogens probably by promoting cell death.
Climate change culminating in increased temperature, sea-level rise, flooding amidst strong winds... more Climate change culminating in increased temperature, sea-level rise, flooding amidst strong winds and heavy rainfall cause mechanical stress (MS) that affects the habitat of several plant species. In response, plants activate a plethora of molecular and physiological processes that alter their architecture causing a phenomenon referred to as thigmomorphogenesis. Plants develop thicker stem, smaller leaves, reduced height and overall increased in tensile strength. These alterations facilitate forest trees to survive windthrows and mitigate subsequent stress. Plants can desensitise their molecular response to repetitive MS, as an adaptive mechanism to prevent unwanted thigmomorphogenesis. Plants may want to ‘remember’ MS since it is natural ubiquitous stress stimuli that occur daily, be it from insect feeding, high winds, animal stamping or heavy rainfall. For more than a century, in Japan and China, stamping on crops, as a form of MS has been used to harden crops against extreme weat...
A single event of mechanical stimulation is perceived by mechanoreceptors that transduce rapid tr... more A single event of mechanical stimulation is perceived by mechanoreceptors that transduce rapid transient signalling to regulate gene expression. Prolonged mechanical stress for days to weeks culminates in cellular changes that strengthen the plant architecture leading to thigmomorphogenesis. The convergence of multiple signalling pathways regulates mechanically induced tolerance to numerous biotic and abiotic stresses. Emerging evidence showed prolonged mechanical stimulation can modify the baseline level of gene expression in naive tissues, heighten gene expression, and prime disease resistance upon a subsequent pathogen encounter. The phenotypes of thigmomorphogenesis can persist throughout growth without continued stimulation, revealing somatic‐stress memory. Epigenetic processes regulate TOUCH gene expression and could program transcriptional memory in differentiating cells to program thigmomorphogenesis. We discuss the early perception, gene regulatory and phytohormone pathways...
Carotenoids are secondary metabolites synthesized in plastids that function in photosynthesis, ph... more Carotenoids are secondary metabolites synthesized in plastids that function in photosynthesis, photoprotection, growth and development of plants. Carotenoids contribute to the yellowish, orange and pinkish-red hues of leaves, flowers and fruits, as well as various aromas. They provide substrates for the biosynthesis of phytohormones and are cleavable into smaller apocarotenoids that function as retrograde signals and/or mediate intracellular communication as well as regulate gene transcription and/or protein translation. Carotenoid biosynthesis and gene regulation are tightly coordinated with tissue-specific plastid differentiation, seedling morphogenesis, fruit development, and prevailing environmental growth conditions such as light, temperature and mycorrhizal interactions. In the last decade, epigenetic processes have been linked to the regulation of carotenoid biosynthesis, accumulation and degradation during plant development. Next-generation sequencing approaches have shed new light on key rate-limiting steps in carotenoid pathways targeted by epigenetic modifications that synchronize carotenoid accumulation with plastid development and morphogenesis. We discuss how histone modifications (methylation and acetylation), DNA methylation and demethylation, as well as small RNA gene silencing processes can modulate carotenoid biosynthesis, accumulation and apocarotenoid generation throughout the life cycle of plant from seed germination to fruit morphogenesis. This review highlights how apocarotenoid signals regulate plastid biogenesis and gene expression in sync with chromatin alterations during skoto-and photomorphogenesis. We provide a new perspective based upon emerging evidence that supports a likely role for carotenoids in contributing to the programming and/or maintenance of the plants' epigenetic landscape.
Twenty five accessions of okra collected in Ghana were evaluated for phenotypic identity, diversi... more Twenty five accessions of okra collected in Ghana were evaluated for phenotypic identity, diversity and quality based on morphological characters. Qualitative and quantitative characteristics were measured and scored as specified by the standard international crop descriptor for okra. A dendrogram was generated for morphological data based on the simple matching coefficient, and four cluster groups were observed. The distribution of the accessions into the groups, based on the morphological traits had no unique geographical relationship. The results of the matrix of similarity among the 25 accessions performed by NTsys pc programme placed two accessions in a tie, suggesting that, they were identical. Eight accessions were placed at above 80% similarity, meaning that, the accession pairs were closely related, and three accessions were 50% similar, which means they matched at half the characters measured. Six pairs of accessions measured were somewhat diverse, which can be exploited b...
Twenty-five accessions of okra collected from different parts of Ghana were evaluated for their h... more Twenty-five accessions of okra collected from different parts of Ghana were evaluated for their horticultural and agronomic attributes in the major and minor cropping seasons of 2008 at the crop and soil sciences experimental field, Kwame Nkrumah University of Science and Technology (KNUST) Kumasi, Ghana, using a randomized complete block design (RCBD) with four replications. The objectives of the experiment were to investigate the horticultural characteristics and performance of all the okra entries. Data collected included fruit and leaf characteristics; Days to first flowering, first flowering node, first fruit-producing node, fresh fruit weight, fruit length at maturity, fruit width, maximum plant height, number of internode, number of seeds per fruit, number of total fruits per plant, seed yield, 100 seed weight. The accessions KNUST/SL1/07Nkrumahene, DA/08/02Dikaba and GH 5787Asontem, GH6102Fetri and 'Asontem' showed number of days from sowing to first-flowering at between 44.00 and 48.00 days, first flowering and fruiting nodes at between 5.00 and 6.00th nodes, days to 50% emergence at 8 days after sowing, the average number to total fruits per plant at 60.00 to 145.00 fruits and green immature fruit colour. The results showed that most of the okra displayed symptoms of okra mosaic virus (OMV) and okra leaf curl virus (OLCV). Fruit size varied among the entries. A correlation of the characters with the total fruit production showed that plant height, days to flowering and nodulation, fruit yield and seed yield recorded positive and significant associations, which generally mean that they influenced fruit production or yield. Specific accessions; KNUST/SL1/07Nkrumahene, DA/08/02Dikaba and GH 5787Asontem, GH6102Fetri and 'Asontem', identified in this study, could be passed on to breeders for utilization in the okra improvement programmes in Ghana.
Enhancing crop yields is a major challenge because of an increasing human population, climate cha... more Enhancing crop yields is a major challenge because of an increasing human population, climate change, and reduction in arable land. Here, we demonstrate that long-lasting growth enhancement and increased stress tolerance occur by pretreatment of dark grown Arabidopsis seedlings with ethylene before transitioning into light. Plants treated this way had longer primary roots, more and longer lateral roots, and larger aerial tissue and were more tolerant to high temperature, salt, and recovery from hypoxia stress. We attributed the increase in plant growth and stress tolerance to ethylene-induced photosynthetic-derived sugars because ethylene pretreatment caused a 23% increase in carbon assimilation and increased the levels of glucose (266%), sucrose/trehalose (446%), and starch (87%). Metabolomic and transcriptomic analyses several days posttreatment showed a significant increase in metabolic processes and gene transcripts implicated in cell division, photosynthesis, and carbohydrate m...
Heterotrimeric G-proteins, consisting of Gα, Gβ and Gγ subunits, are important signal transducers... more Heterotrimeric G-proteins, consisting of Gα, Gβ and Gγ subunits, are important signal transducers in eukaryotes. In plants, G-protein-mediated signaling contributes to defense against a range of fungal and bacterial pathogens. Here we studied response of G-protein-deficient mutants to ssRNA viruses representing 2 different families: Cucumber mosaic virus (CMV) (Bromoviridae) and Turnip mosaic virus (TuMV) (Potyviridae). We found that development of spreading necrosis on infected plants was suppressed in the Gβ-deficient mutant (agb1-2) compared to wild type and Gα-deficient mutant (gpa1-4). In accordance, ion leakage caused by viral infection was also significantly reduced in agb1-2 compared to wild type and gpa1-4. Nevertheless, both viruses replicated better in agb1-2 plants, while gpa1-4 was similar to wild type. Analysis of pathogenesis-related genes showed that Gβ negatively regulated salicylic acid, jasmonic acid and abscisic acid marker genes during CMV and TuMV infections. I...
In animals, heterotrimeric G proteins, comprising Ga, Gb, and Gg subunits, are molecular switches... more In animals, heterotrimeric G proteins, comprising Ga, Gb, and Gg subunits, are molecular switches whose function tightly depends on Ga and Gbg interaction. Intriguingly, in Arabidopsis (Arabidopsis thaliana), multiple defense responses involve Gbg, but not Ga. We report here that the Gbg dimer directly partners with extra-large G proteins (XLGs) to mediate plant immunity. Arabidopsis mutants deficient in XLGs, Gb, and Gg are similarly compromised in several pathogen defense responses, including disease development and production of reactive oxygen species. Genetic analysis of double, triple, and quadruple mutants confirmed that XLGs and Gbg functionally interact in the same defense signaling pathways. In addition, mutations in XLG2 suppressed the seedling lethal and cell death phenotypes of BRASSINOSTEROID INSENSITIVE1-associated receptor kinase1-interacting receptor-like kinase1 mutants in an identical way as reported for Arabidopsis Gb-deficient mutants. Yeast (Saccharomyces cerevisiae) three-hybrid and bimolecular fluorescent complementation assays revealed that XLG2 physically interacts with all three possible Gbg dimers at the plasma membrane. Phylogenetic analysis indicated a close relationship between XLGs and plant Ga subunits, placing the divergence point at the dawn of land plant evolution. Based on these findings, we conclude that XLGs form functional complexes with Gbg dimers, although the mechanism of action of these complexes, including activation/deactivation, must be radically different form the one used by the canonical Ga subunit and are not likely to share the same receptors. Accordingly, XLGs expand the repertoire of heterotrimeric G proteins in plants and reveal a higher level of diversity in heterotrimeric G protein signaling.
BackgroundProlonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation respo... more BackgroundProlonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation response associated with increased disease resistance. What remains unclear is if; 1) plants pre-exposed to a short period of repetitive MS can prime defence responses upon subsequent challenge with necrotrophic pathogens, 2) MS mediates plant immunity via jasmonic acid (JA) signalling, and 3) a short period of repetitive MS can cause long-term changes in gene expression resembling a stress-induced memory. To address these points, 10-days old juvenileArabidopsisseedlings were mechanically stressed for 7-days using a soft brush and subsequently challenged with the necrotrophic pathogens,Alternaria brassicicola,andBotrytis cinerea. Here we assessed how MS impacted structural cell wall appositions, disease symptoms and altered gene expression in response to infection.ResultsThe MS-treated plants exhibited enhanced cell wall appositions and jasmonic acid (JA) accumulation that correlated with a r...
Heterotrimeric G-proteins, consisting of Ga, Gb and Gg subunits, are important signal transducers... more Heterotrimeric G-proteins, consisting of Ga, Gb and Gg subunits, are important signal transducers in eukaryotes. In plants, G-protein-mediated signaling contributes to defense against a range of fungal and bacterial pathogens. Here we studied response of G-protein-deficient mutants to ssRNA viruses representing 2 different families: Cucumber mosaic virus (CMV) (Bromoviridae) and Turnip mosaic virus (TuMV) (Potyviridae). We found that development of spreading necrosis on infected plants was suppressed in the Gb-deficient mutant (agb1-2) compared to wild type and Ga-deficient mutant (gpa1-4). In accordance, ion leakage caused by viral infection was also significantly reduced in agb1-2 compared to wild type and gpa1-4. Nevertheless, both viruses replicated better in agb1-2 plants, while gpa1-4 was similar to wild type. Analysis of pathogenesis-related genes showed that Gb negatively regulated salicylic acid, jasmonic acid and abscisic acid marker genes during CMV and TuMV infections. Interestingly, analysis of salicylic acid deficient transgenic plants indicated that salicylic acid did not affect resistance against these viruses and did not influence the Gb-mediated defense response. We conclude that heterotrimeric G-proteins play a positive role in defense against viral pathogens probably by promoting cell death.
Background: Prolonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation res... more Background: Prolonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation response associated with increased disease resistance. What remains unclear is if; 1) plants pre-exposed to a short period of repetitive MS can prime defence responses upon subsequent challenge with necrotrophic pathogens, 2) MS mediates plant immunity via jasmonic acid (JA) signalling, and 3) a short period of repetitive MS can cause longterm changes in gene expression resembling a stress-induced memory. To address these points, 10-days old juvenile Arabidopsis seedlings were mechanically stressed for 7-days using a soft brush and subsequently challenged with the necrotrophic pathogens, Alternaria brassicicola, and Botrytis cinerea. Here we assessed how MS impacted structural cell wall appositions, disease symptoms and altered gene expression in response to infection. Results: The MS-treated plants exhibited enhanced cell wall appositions and jasmonic acid (JA) accumulation that correlated with a reduction in disease progression compared to unstressed plants. The expression of genes involved in JA signalling, callose deposition, peroxidase and phytoalexin biosynthesis and reactive oxygen species detoxification were hyper-induced 4-days post-infection in MS-treated plants. The loss-of-function in JA signalling mediated by the JA-insensitive coronatine-insensitive 1 (coi1) mutant impaired the hyper-induction of defense gene expression and promoted pathogen proliferation in MS-treated plants subject to infection. The basal expression level of PATHOGENESIS-RELATED GENE 1 and PLANT DEFENSIN 1.2 defense marker genes were constitutively upregulated in rosette leaves for 5-days post-MS, as well as in naïve cauline leaves that differentiated from the inflorescence meristem well after ceasing MS. Conclusion: This study reveals that exposure of juvenile Arabidopsis plants to a short repetitive period of MS can alter gene expression and prime plant resistance upon subsequent challenge with necrotrophic pathogens via the JA-mediated COI1 signalling pathway. MS may facilitate a stress-induced memory to modulate the plant's response to future stress encounters. These data advance our understanding of how MS primes plant immunity against necrotrophic pathogens and how that could be utilised in sustainable agricultural practices.
Background: Prolonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation res... more Background: Prolonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation response associated with increased disease resistance. What remains unclear is if; 1) plants pre-exposed to a short period of repetitive MS can prime defence responses upon subsequent challenge with necrotrophic pathogens, 2) MS mediates plant immunity via jasmonic acid (JA) signalling, and 3) a short period of repetitive MS can cause longterm changes in gene expression resembling a stress-induced memory. To address these points, 10-days old juvenile Arabidopsis seedlings were mechanically stressed for 7-days using a soft brush and subsequently challenged with the necrotrophic pathogens, Alternaria brassicicola, and Botrytis cinerea. Here we assessed how MS impacted structural cell wall appositions, disease symptoms and altered gene expression in response to infection. Results: The MS-treated plants exhibited enhanced cell wall appositions and jasmonic acid (JA) accumulation that correlated with a reduction in disease progression compared to unstressed plants. The expression of genes involved in JA signalling, callose deposition, peroxidase and phytoalexin biosynthesis and reactive oxygen species detoxification were hyper-induced 4-days post-infection in MS-treated plants. The loss-of-function in JA signalling mediated by the JA-insensitive coronatine-insensitive 1 (coi1) mutant impaired the hyper-induction of defense gene expression and promoted pathogen proliferation in MS-treated plants subject to infection. The basal expression level of PATHOGENESIS-RELATED GENE 1 and PLANT DEFENSIN 1.2 defense marker genes were constitutively upregulated in rosette leaves for 5-days post-MS, as well as in naïve cauline leaves that differentiated from the inflorescence meristem well after ceasing MS. Conclusion: This study reveals that exposure of juvenile Arabidopsis plants to a short repetitive period of MS can alter gene expression and prime plant resistance upon subsequent challenge with necrotrophic pathogens via the JA-mediated COI1 signalling pathway. MS may facilitate a stress-induced memory to modulate the plant's response to future stress encounters. These data advance our understanding of how MS primes plant immunity against necrotrophic pathogens and how that could be utilised in sustainable agricultural practices.
Enhancing crop yields is a major challenge because of an increasing human population, climate cha... more Enhancing crop yields is a major challenge because of an increasing human population, climate change, and reduction in arable land. Here, we demonstrate that long-lasting growth enhancement and increased stress tolerance occur by pretreatment of dark grown Arabidopsis seedlings with ethylene before transitioning into light. Plants treated this way had longer primary roots, more and longer lateral roots, and larger aerial tissue and were more tolerant to high temperature, salt, and recovery from hypoxia stress. We attributed the increase in plant growth and stress tolerance to ethylene-induced photosynthetic-derived sugars because ethylene pretreatment caused a 23% increase in carbon assimilation and increased the levels of glucose (266%), sucrose/trehalose (446%), and starch (87%). Metabolomic and transcriptomic analyses several days posttreatment showed a significant increase in metabolic processes and gene transcripts implicated in cell division, photosynthesis, and carbohydrate metabolism. Because of this large effect on metabolism, we term this “ethylene-mediated metabolic priming.” Reducing photosynthesis with inhibitors or mutants prevented the growth enhancement, but this was partially rescued by exogenous sucrose, implicating sugars in this growth phenomenon. Additionally, ethylene pretreatment increased the levels of CINV1 and CINV2 encoding invertases that hydrolyze sucrose, and cinv1; cinv2 mutants did not respond to ethylene pretreatment with increased growth indicating increased sucrose breakdown is critical for this trait. A model is proposed where ethylene-mediated metabolic priming causes long-term increases in photosynthesis and carbohydrate utilization to increase growth. These responses may be part of the natural development of seedlings as they navigate through the soil to emerge into light.
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Papers by Eric Brenya
Here, we demonstrate that long-lasting growth enhancement and increased stress tolerance occur by pretreatment of dark grown
Arabidopsis seedlings with ethylene before transitioning into light. Plants treated this way had longer primary roots, more and longer
lateral roots, and larger aerial tissue and were more tolerant to high temperature, salt, and recovery from hypoxia stress. We
attributed the increase in plant growth and stress tolerance to ethylene-induced photosynthetic-derived sugars because ethylene
pretreatment caused a 23% increase in carbon assimilation and increased the levels of glucose (266%), sucrose/trehalose (446%), and
starch (87%). Metabolomic and transcriptomic analyses several days posttreatment showed a significant increase in metabolic
processes and gene transcripts implicated in cell division, photosynthesis, and carbohydrate metabolism. Because of this large effect
on metabolism, we term this “ethylene-mediated metabolic priming.” Reducing photosynthesis with inhibitors or mutants prevented
the growth enhancement, but this was partially rescued by exogenous sucrose, implicating sugars in this growth phenomenon.
Additionally, ethylene pretreatment increased the levels of CINV1 and CINV2 encoding invertases that hydrolyze sucrose, and cinv1;
cinv2 mutants did not respond to ethylene pretreatment with increased growth indicating increased sucrose breakdown is critical for
this trait. A model is proposed where ethylene-mediated metabolic priming causes long-term increases in photosynthesis and carbohydrate utilization to increase growth. These responses may be part of the natural development of seedlings as they navigate
through the soil to emerge into light.
Here, we demonstrate that long-lasting growth enhancement and increased stress tolerance occur by pretreatment of dark grown
Arabidopsis seedlings with ethylene before transitioning into light. Plants treated this way had longer primary roots, more and longer
lateral roots, and larger aerial tissue and were more tolerant to high temperature, salt, and recovery from hypoxia stress. We
attributed the increase in plant growth and stress tolerance to ethylene-induced photosynthetic-derived sugars because ethylene
pretreatment caused a 23% increase in carbon assimilation and increased the levels of glucose (266%), sucrose/trehalose (446%), and
starch (87%). Metabolomic and transcriptomic analyses several days posttreatment showed a significant increase in metabolic
processes and gene transcripts implicated in cell division, photosynthesis, and carbohydrate metabolism. Because of this large effect
on metabolism, we term this “ethylene-mediated metabolic priming.” Reducing photosynthesis with inhibitors or mutants prevented
the growth enhancement, but this was partially rescued by exogenous sucrose, implicating sugars in this growth phenomenon.
Additionally, ethylene pretreatment increased the levels of CINV1 and CINV2 encoding invertases that hydrolyze sucrose, and cinv1;
cinv2 mutants did not respond to ethylene pretreatment with increased growth indicating increased sucrose breakdown is critical for
this trait. A model is proposed where ethylene-mediated metabolic priming causes long-term increases in photosynthesis and carbohydrate utilization to increase growth. These responses may be part of the natural development of seedlings as they navigate
through the soil to emerge into light.