Papers by Gozal Ben-hayyim
Several genes encoding putative glutathione peroxidase have been isolated from a variety of plant... more Several genes encoding putative glutathione peroxidase have been isolated from a variety of plants, all of which show the highest homology to the phospholipid hydroperoxide isoform. Several observations suggest that the proteins are involved in biotic and abiotic stress responses. Previous studies on the regulation of gpx1, the Citrus sinensis gene encoding phospholipid hydroperoxide isoform, led to the conclusion that
Plant cell reports, 1989
Plantlets were regenerated from a selected salt-tolerant cell line of Shamouti orange (Citrus sin... more Plantlets were regenerated from a selected salt-tolerant cell line of Shamouti orange (Citrus sinensis L. Osbeck). Embryogenesis was carried out both in the presence and absence of NaCl, yielding green and white globular embryos, respectively. Greening could be induced subsequently and normal heart shape embryo development was obtained. Plantlet formation required exposure to kinetin prior to the introduction of the root-inducing hormone naphthalene acetic acid. This system differs from the designed protocol for plant regeneration from the salt-sensitive, i.e., unselected callus. It is concluded that NaCl interferes with the regeneration process, with embryogenesis and/or embryo development into plantlets. Its presence during callus growth probably changes the balance of the phytohormones which is later manifested in plant regeneration. Citrus salt-tolerant callus yields salt-tolerant embryos. Salt-tolerant calli derived from regenerated plantlets indicate acquisition of salt tolera...
The Plant Journal, 2005
Changes in the degree of fatty acid (FA) desaturation are implicated in plant responses to variou... more Changes in the degree of fatty acid (FA) desaturation are implicated in plant responses to various abiotic stresses, including heat, salt and drought. However, it is still not known whether decreased levels of linolenic acid, found in many plants subjected to salt and drought stress, reflect a mechanism of defence or damage. We addressed this question by generating tobacco cells and plants ectopically overexpressing two FA desaturases: the cytosolic FAD3 or the plastidic FAD8. A remarkable increase in the ratio of total linolenic to linoleic acids resulted from overexpression of FAD3, whereas ectopic overexpression of FAD8 induced an increased ratio mainly in the plastidic lipids. Here we present evidence that overexpressing FAD8 imposes much greater heat sensitivity than does FAD3 overexpression, in both cultured cells and whole plants. Overexpression of either FAD3 or FAD8 increases tolerance to drought in tobacco plants and to osmotic stress in cultured cells. These findings suggest that a drought-induced decreased level of linolenic acid reflects damage. Our results point to the potential of exploiting FAD overexpression as a tool to ameliorate drought tolerance.
Planta, 2008
Detrimental effects of salinity on plants are known to be partially alleviated by external Ca(2+)... more Detrimental effects of salinity on plants are known to be partially alleviated by external Ca(2+). Previously we demonstrated that in citrus cells, phospholipid hydroperoxide glutathione peroxidase (GPX1) is induced by salt and its activation can be monitored by pGPX1::GUS fusion in transformed tobacco cells. In this paper we further characterized the induction of GPX1 by additional treatments, which are known to affect Ca(2+) transport. Omission of Ca(2+) changed the pattern of the transient salt-induced expression of GPX1 and chelation of Ca(2+) by EGTA, or treatment with caffeine, abolished the salt-induced GPX1 transcript. On the other hand, La(3+) was found to be as potent as NaCl in inducing GPX1 transcription and the combined effect of La(3+) and NaCl seemed to be additive. Pharmacological perturbation of either external or internal Ca(2+) pools by La(3+), EGTA, caffeine, Ca(2+) channel blockers, or a Ca(2+)-ATPase inhibitor rendered the imposed salt stress more severe. Except for La(3+), all these Ca(2+) effectors had no effect on their own. In addition, the fluidizer benzyl alcohol dramatically increased the NaCl-induced GPX1 transcription. Taken together, our results show that: 1) the mode of action of La(3+) on GPX1 expression differs from its established role as a Ca(2+) channel blocker, 2) membrane integrity has an important role in the perception of salt stress, and 3) internal stores of Ca(2+) are involved in activating GPX1 expression in response to salt stress. We propose that the common basis for these effects lies in the membrane bound Ca(2+).
Planta, 1999
Recent ®ndings in our laboratory showed that in citrus cells, salt treatment induced the accumula... more Recent ®ndings in our laboratory showed that in citrus cells, salt treatment induced the accumulation of mRNA and a protein corresponding to phospholipid hydroperoxide glutathione peroxidase (PHGPX), an enzyme active in the cellular antioxidant system. The protein and its encoding gene, csa, were isolated and characterized, and the expected enzymatic activity was demonstrated (G. Ben-Hayyim et al., 1993, Plant Sci. 88: 129±140; D. Holland et al., 1993, Plant Mol. Biol. 21: 923±927; D. Holland et al., 1994, FEBS Lett. 337: 52±55; T. Beeor-Tzahar et al., 1995, FEBS Lett. 366: 151±155). In an attempt to ®nd out how salt induces the expression of an antioxidant enzyme, the regulation of PHGPX in citrus cells was studied at both the mRNA transcript and the protein levels. A high and transient response at the csa mRNA level was observed after 4±7 h of exposing salt-sensitive cells to NaCl, or abscisic acid, whereas no response could be detected in the salt-tolerant cells under the same conditions. tert-Butylhydroperoxide, a substrate of PHGPX, induced csa mRNA transcripts after only 2 h, and abolished the dierential response between salt-sensitive and salttolerant cells. On the basis of these results and those obtained under heat and cold stresses, it is suggested that csa is directly induced by the substrate of its encoded enzyme PHGPX, and that salt induction occurs mainly via the production of reactive oxygen species and hydroperoxides.
Planta, 1997
Salt damage to plants has been attributed to a combination of several factors including mainly os... more Salt damage to plants has been attributed to a combination of several factors including mainly osmotic stress and the accumulation of toxic ions. Recent findings in our laboratory showed that phospholipid hydroperoxide glutathione peroxidase (PHGPX), an enzyme active in the cellular antioxidant system, was induced by salt in citrus cells and mainly in roots of plants. Following this observation we studied the two most important enzymes active in elimination of reactive oxygen species, namely, superoxide dismutase (SOD) and ascorbate peroxidase (APX), to determine whether a general oxidative stress is induced by salt. While Cu/Zn-SOD activity and cytosolic APX protein level were similarly induced by salt and methyl viologen, the response of PHGPX and other APX isozymes was either specific to salt or methyl viologen, respectively. Unlike PHGPX, cytosolic APX and Cu/Zn-SOD were not induced by exogenously added abscisic acid. Salt induced a significant increase in SOD activity which was not matched by the subsequent enzyme APX. We suggest that the excess of H2O2 interacts with lipids to form hydroperoxides which in turn induce and are removed by PHGPX. Ascorbate peroxidase seems to be a key enzyme in determining salt tolerance in citrus as its constitutive activity in salt-sensitive callus is far below the activity observed in salt-tolerant callus, while the activities of other enzymes involved in the defence against oxidative stress, namely SOD, glutathione reductase and PHGPX, are essentially similar.
Planta, 2001
Recent findings in our laboratory suggested that in citrus cells the salt induction of phospholip... more Recent findings in our laboratory suggested that in citrus cells the salt induction of phospholipid hydroperoxide glutathione peroxidase, an enzyme active in cellular antioxidant defense, is mediated by the accumulation of hydroperoxides. Production of hydroperoxides occurs as a result of non-enzymatic auto-oxidation or via the action of lipoxygenases (LOXs). In an attempt to resolve the role of LOX activity in the accumulation of peroxides we analyzed the expression of this protein under stress conditions and in cells of Citrus sinensis L. differing in sensitivity to salt. Lipoxygenase expression was induced very rapidly only in the salt-tolerant cells and in a transient manner. The induction was specific to salt stress and did not occur with other osmotic-stress-inducing agents, such as polyethylene glycol or mannitol, or under hot or cold conditions, or in the presence of abscisic acid. The induction was eliminated by the antioxidants dithiothreitol and kaempferol, thus once more establishing a correlation between salt and oxidative stresses. Analyses of both in vitro and in vivo products of LOX revealed a specific 9-LOX activity, and a very fast reduction of the hydroperoxides to the corresponding hydroxy derivatives. This suggests that one of the metabolites further downstream in the reductase pathway may play a key role in triggering defense responses against salt stress.
Plant Science, 1993
... Isolation and characterization of salt-associated protein in Citrus Gozal Ben-Hayyima, Zehava... more ... Isolation and characterization of salt-associated protein in Citrus Gozal Ben-Hayyima, Zehava Faltina, Shimon Gepsteinb, Luc Camoinc, A. Donny Strosbergc and Yuval Eshdata ... 27 Y. Li and DC Walton, Xanthophylls and abscisic acid biosynthesis in water-stressed bean leaves ...
Plant Science, 2002
In previous studies, we showed that a short hot water treatment (at 62 8C for 20 s) increased chi... more In previous studies, we showed that a short hot water treatment (at 62 8C for 20 s) increased chilling tolerance in grapefruit. In order to gain more insight into the molecular mechanisms involved in heat-induced chilling tolerance responses, we performed cDNA differential display analysis and isolated a 600-bp polymerase chain reaction (PCR) fragment whose expression was enhanced 24 h after the heat treatment, and that showed high sequence homology with the 5? region of various NHX1 vacuolar Na ' /H ' antiporter genes. The full-length cDNA sequence of cNHX1 (for citrus NHX1 ) was further isolated by 3?-RACE; it had a total length of 2135 bp with an open reading frame of 1626 bp, and encoded a predicted polypetide of 542 amino acids with a molecular mass of 59.8 kDa. The cNHX1 protein shares 83, 78 and 56% identity with the other recently isolated Arabidopsis thaliana , Atriplex gmelini and Oryza sativa NHX1 proteins, respectively. It has been reported that the Arabidopsis AtNHX1 gene partially complemented a salt-sensitive yeast mutation and that overexpression of this gene significantly increased salt tolerance in transgenic plants. In the current study, we showed that the expression of the cNHX1 gene was temporarily induced by a heat treatment, and that its mRNA levels markedly increase during a 6-week cold storage period at 2 8C in heat-treated fruit but not in control untreated fruit, thus suggesting its possible involvement in heat-induced chilling tolerance responses. The expression of the cNHX1 gene was also markedly induced by salt stress, but not by other stresses, such as exposure to ethylene or UV irradiation. #
PLANT PHYSIOLOGY, 1985
Four selected NaCl-tolerant cell lines of Sour orange (Citrus aurantium) were compared with the n... more Four selected NaCl-tolerant cell lines of Sour orange (Citrus aurantium) were compared with the nonselected cell line in their growth and internal ion content of Na(+), K(+), and Cl(-) when exposed to increasing NaCl concentrations. No difference was found among the various NaCl-tolerant cell lines in Na(+) and Cl(-) uptake, and all these cell lines took up similar or even larger amounts of Na(+) and Cl(-) than the NaCl-sensitive cell line. Exposure of cells of NaCl-sensitive and NaCl-tolerant lines to equal external concentrations of NaCl, resulted in a greater loss of K(+) from the NaCl-sensitive cell line. This observation leads to the conclusion that growth and ability to retain high levels of internal K(+) are correlated. Exposure of the NaCl-tolerant cell lines to salts other than NaCl resulted in even greater tolerance to Na(2)SO(4), but rather poor tolerance to K(+) introduced as either K(2)SO(4) or KCl; the latter has a stronger inhibitory effect. The NaCl-sensitive cell line proved to be more sensitive to replacement of Na(+) by K(+). Analyses of internal Na(+), K(+), and Cl(-) concentrations failed to identify any particular internal ion concentration which could serve as a reliable marker for salt tolerance.
Plant Molecular Biology, 1993
A gene encoding for a citrus salt-stress-associated protein (Cit-SAP) was cloned from Citrus sine... more A gene encoding for a citrus salt-stress-associated protein (Cit-SAP) was cloned from Citrus sinensis salt-treated cell suspension. The gene, designated csa, was isolated from a cDNA expression library. The partial amino acid sequence of the protein, as well as that deduced from the nucleotide sequence of csa, revealed a considerable homology to mammalian glutathione peroxidase (GP), and to clone 6P229 from tobacco protoplasts. The increased expression of Cit-SAP in NaCl-treated cultured citrus cells and in citrus plants irrigated with saline water, and its similarity to GP, raise the possibility that one of the effects of salt stress in plants may be the increase of the level of free radicals.
Plant Molecular Biology, 1995
In a search for genes that are induced in citrus cell suspension in response to salt stress, a cD... more In a search for genes that are induced in citrus cell suspension in response to salt stress, a cDNA clone with high homology to cotton Lea5 gene was isolated. Data base analysis of the protein deduced from the nucleotide sequence indicates that, like in cotton, the protein from citrus contains regions with significant hydropathic character. The gene, designated C-Lea5, is expressed in citrus leaves as well as cell suspension. The steady-state level of C-Lea5 is increased in cell suspension that is grown in the presence of 0.2 M NaC1. This phenomenon is also observed in leaves of citrus plants irrigated with NaC1 and in citrus seedlings which are exposed to drought and heat stress. We suggest that the osmotic stress resulted from elevated level of salt is responsible for the increase in the level of C-Lea5.
Physiologia Plantarum, 1998
Physiologia Plantarum, 1994
Pesticide Biochemistry and Physiology, 2000
Glutathione peroxidase is involved in scavenging free radicals in many biological systems. Its pr... more Glutathione peroxidase is involved in scavenging free radicals in many biological systems. Its presence in plants has been implicated by identification of genes with nucleotide sequences similar to those of mammals, as well as by indirect, coupled enzyme assays. We directly quantified glutathione peroxidase activity in crude plant extracts using an organic hydroperoxide substrate and measuring GSSG, the direct reaction
Gene, 1995
A cDNA clone (C3) with high homology to plant oleosins was isolated from citrus cultured cells. T... more A cDNA clone (C3) with high homology to plant oleosins was isolated from citrus cultured cells. The 827-bp cDNA insert has an open reading frame of 144 amino-acid residues. The central hydrophobic domain of the protein is nearly identical to oleosins from Brassica napus and maize, and the C-terminal hydrophilic region following the hydrophobic domain is also highly conserved. The steady-state level of mRNA hybridizing to C3 was significantly increased upon exposure of citrus cells to 0.2 M NaCl. A lower level of transcript was found in seeds, but none could be detected in any other vegetative tissue (leaves, roots or fruit) even in the presence of salt under the conditions used. The induction of the oleosin homologue in citrus cells by salt does not depend on the developmental stage of the cells.
Colloids and Surfaces B: Biointerfaces, 1999
To gain a better understanding of the relations between root elongation and the amount of Ca 2+ b... more To gain a better understanding of the relations between root elongation and the amount of Ca 2+ bound to the plasma membrane (PM), melon plants were grown in aerated solutions containing different concentrations of CaCl 2 with various concentrations of NaCl or mannitol. With increasing external concentrations of NaCl or mannitol, root elongation was suppressed. Addition of CaCl 2 to the external medium alleviated the inhibition of root elongation by high concentrations of Na + , but not of mannitol. Root elongation in media containing high concentrations of NaCl was correlated with the computed amount of Ca 2+ bound to the PM. A model describing relative root elongation (RRL) under salt stress was developed. This model takes into account the osmotic potential in the growing solution (based on the mannitol experiments) and the computed amount of Ca 2+ bound to the PM. Calcium binding was calculated by applying a Gouy-Chapman-Stern sorption model using the same parameters deduced from studies on PM vesicles. This model combines electrostatic theory with competitive binding at the PM surface. The model for RRL allowed the computation of a critical value for the fraction of negative sites binding Ca 2+ on the PM needed for nearly optimal (95%) root elongation. Any decrease below this critical value decreased the RRL. Root elongation of Honey Dew (salt-resistant cv.) was greater than that of Eshkolit Ha'Amaqim (salt-sensitive cv.) under NaCl stress. Nearly optimal root growth for Honey Dew and Eshkolit Ha'Amaqim occurred when 40% and 51% of total membrane charged sites were bound by Ca 2+ , respectively. The effect of osmotic potential on the suppression of root elongation was the same for the two cultivars. To our knowledge, this report provides the first fully quantitative estimates of PM-bound Ca 2+ relative to salt toxicity.
To gain a better understanding of the relations between root elongation and the amount of Ca 2+ b... more To gain a better understanding of the relations between root elongation and the amount of Ca 2+ bound to the plasma membrane (PM), melon plants were grown in aerated solutions containing different concentrations of CaCl 2 with various concentrations of NaCl or mannitol. With increasing external concentrations of NaCl or mannitol, root elongation was suppressed. Addition of CaCl 2 to the external medium alleviated the inhibition of root elongation by high concentrations of Na + , but not of mannitol. Root elongation in media containing high concentrations of NaCl was correlated with the computed amount of Ca 2+ bound to the PM. A model describing relative root elongation (RRL) under salt stress was developed. This model takes into account the osmotic potential in the growing solution (based on the mannitol experiments) and the computed amount of Ca 2+ bound to the PM. Calcium binding was calculated by applying a Gouy-Chapman-Stern sorption model using the same parameters deduced from studies on PM vesicles. This model combines electrostatic theory with competitive binding at the PM surface. The model for RRL allowed the computation of a critical value for the fraction of negative sites binding Ca 2+ on the PM needed for nearly optimal (95%) root elongation. Any decrease below this critical value decreased the RRL. Root elongation of Honey Dew (salt-resistant cv.) was greater than that of Eshkolit Ha'Amaqim (salt-sensitive cv.) under NaCl stress. Nearly optimal root growth for Honey Dew and Eshkolit Ha'Amaqim occurred when 40% and 51% of total membrane charged sites were bound by Ca 2+ , respectively. The effect of osmotic potential on the suppression of root elongation was the same for the two cultivars. To our knowledge, this report provides the first fully quantitative estimates of PM-bound Ca 2+ relative to salt toxicity.
Advances in Molecular Breeding Toward Drought and Salt Tolerant Crops, 2007
Page 1. CHAPTER 25 RECENT ADVANCES IN BREEDING CITRUS FOR DROUGHT AND SALINE STRESS TOLERANCE GOZ... more Page 1. CHAPTER 25 RECENT ADVANCES IN BREEDING CITRUS FOR DROUGHT AND SALINE STRESS TOLERANCE GOZAL BEN-HAYYIM1AND GLORIA A. MOORE2 1Institute of Plant Sciences, Agricultural Research ...
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Papers by Gozal Ben-hayyim