Promoter polymorphism in FAE1.1 and FAE1.2 genes associated with erucic acid content in Brassica juncea

摘要

FAE1, the gene encoding fatty acid elongase, has been implicated to play a decisive role in the synthesis of erucic acid. Allelic variations in this gene, such as single nucleotide polymorphisms (SNPs), insertions/deletions (InDels), and insertions of transposable element (TE), are predominantly responsible for variability in erucic acid content in the seed, among the Brassica genotypes. Brassica juncea being an amphidiploid, contains two paralogs, FAE1.1 and FAE1.2. Although the coding DNA sequences (CDS) of FAE gene is highly conserved (>95% identical), the promoter region is found to be polymorphic. The sequence variability in the promoter region of FAE1 across different Brassica spp. suggests their likely involvement in the regulation of the gene expression. This study was aimed to evaluate polymorphism in the upstream region of FAE1.1 and FAE1.2 genes, across the low erucic acid (LEA) and high erucic acid (HEA) cultivars, and to develop molecular markers based on this variability. The upstream regions of FAE were sequenced from LEA cultivar Pusa Mustard 30 and HEA cultivar Pusa Bold. A 28-bp deletion in the promoter of FAE1.1 and a 340-bp insertion of a transposon-like element in the FAE1.2 gene promoter were discovered in LEA genotype. Markers based on the sequence variability in the promoter regions of FAE1.1 and FAE1.2 were found to completely co-segregate with the seed erucic acid content. These markers can be effectively used in marker-assisted selection for development of low erucic acid cultivars in B. juncea.