Brassinosteroid

Brassinosteroids (BRs) are the plant-specific steroidal hormones that regulate a broad spectrum of plant growth and developmental processes under normal conditions and various biotic, and abiotic stresses. BES1 transcription factors regulate the expression of brassinosteroid-responsive genes. Completion of the grape genome sequencing enabled us to undertake a genome-wide identification of the gene families in this plant. Therefore, we performed a genome-wide investigation of BES genes in grape. The physicochemical properties, phylogeny tree, gene structure, conserved motifs, cis-acting elements, miRNA, and gene chip expression of the grape BES1 transcription factors were analyzed using the bioinformatics tools. The results showed that the grape BES1 transcription factors had seven members, which clustered into three subgroups according to the phylogenetic analysis. Each subgroup was well defined by the conserved motifs, implying that close genetic relationships could be identified among the members of each subgroup. According to the chromosomal locations, 1, 1, 2, 1, 1, and 1 genes were located on chromosomes 2, 4, 10, 15, 18, and 19, respectively. The analysis of cis-acting elements indicated that BES1 genes contained response elements of hormones and abiotic stresses, as well as organ-specific elements. The miRNA target analysis indicated that VvBES1-1, VvBES1-3, and VvBES1-5 contained miRNA target position in grape. Gene chip expression profile analysis revealed that the expression patterns of the grape BES1 genes were different in different organs and developmental stages. The analysis of this gene family would provide some theoretical basis for understanding the evolution and function of the BES1 genes in the grape.

The specification of vascular patterning in plants has interested plant biologists for many years, but in the last decade a new context for this interest has emerged. Specifically, recent proposals to engineer C4 traits into C3 plants such as rice demand an understanding of how the distinctive venation pattern in the leaves of C4 plants is elaborated. High vein density with Kranz anatomy, where photosynthetic cells are arranged in encircling layers around vascular bundles, is one of the major traits that differentiate C4 from C3 species. To identify genetic factors that specify C4 leaf anatomy we generated ethyl-methanesulfonate and gamma-ray mutagenized populations of the C4 species sorghum (Sorghum bicolor), and screened for lines with reduced vein density. Two mutations were identified that conferred low vein density. Both mutations segregated in backcrossed F2 populations as homozygous recessive alleles. Bulk segregant analysis using next generation sequencing revealed that in both cases, the mutant phenotype was associated with mutations in the Cytochrome P450 90D2 gene that encodes an enzyme in the brassinosteroid biosynthesis pathway. Lack of complementation in allelism tests confirmed this result. These data indicate that the brassinosteroid pathway promotes high vein density in the sorghum leaf, and suggest that differences between C4 and C3 leaf anatomy may arise in part through differential activity of this pathway in the two leaf types. This article is protected by copyright. All rights reserved.