Genome-Wide Identification of GH3 Genes in Brassica Oleracea and Identification of a Promoter Region for Anther-Specific Expression of a GH3 Gene

Abstract

Background:The Gretchen Hagen 3 (GH3) genes encode acyl acid amido synthetases, many of which have been shown to modulate the amount of active plant hormones or their precursors. GH3 genes, especially Group Ⅲ subgroup 6 GH3 genes, and their expression patterns in economically important kale-type Brassica oleracea have not been systematically identified. Results:As a first step to understand regulation and molecular functions of Group Ⅲ subgroup 6 GH3 genes, thirty-four GH3 genes including four subgroup 6 genes were identified In B. oleracea var. oleracea, using TO1000. Synteny found around subgroup 6 GH3 genes in TO1000 and Arabidopsis indicated that these genes are evolutionarily related. Although expression of four subgroup 6 GH3 genes in TO1000 is not induced by auxin, gibberellic acid, and jasmonic acid, the genes show different organ-dependent expression patterns. Only one TO1000 subgroup 6 GH3 gene, Bo2g011210, is expressed in anthers when microspores, polarized microspores, and bicellular pollens are present, similar to two out of four syntenic Arabidopsis subgroup 6 GH3 genes. Detailed analyses of promoter activities of Bo2g011210 further showed that Bo2g011210 is expressed in tapetal cells and pollens in anther, and also expressed in leaf primordia and floral abscission zones. Conclusions:Sixty-two base pair (bp) region (-340 ~ -279 bp upstream from start codon) and about 450 bp region (-1489 to -1017 bp) in Bo2g011210 promoter were found to be important for expressions in anther and expressions in leaf primordia and floral abscission zones, respectively. The identified anther-specific promoter region will be useful to develop male sterile transgenic Brassica plants.