Variation of five major glucosinolate genes in Brassica rapa in relation to Brassica oleracea and Arabidopsis thaliana

Glucosinolates and their derivatives isothiocyanates are important secondary metabolites in the Brassicacea that has biological activity, such as cancer protecting and biofumigant properties. The putative orthologs of five major genes in the glucosinolate biosynthetic pathway, Bra.GSELONG.a, Bra.GSALK.a, Bra.CYP83B1, Bra.SUR1.a and Bra.ST5.a, were cloned from both cDNA and genomic DNA from different subspecies of Brassica rapa. Interspecies comparative analysis disclosed high conservation of exon number and size for GS-Elong, GS-Alk, GS-CYP83B1 and GS-ST5a among B. rapa, B. oleracea and A. thaliana. Splice site mutations caused the differences observed for exon numbers and sizes in GS-SUR1 among the three species. However, the exonic sequences were highly conserved for this gene. There were not major differences of intronic sizes among the three species for these genes, except for intron 1 for GS-Elong in two subspecies of B. rapa. The cloning of the putative orthologs of all these major genes involved in the glucosinolate biosynthesis pathway of B. rapa and sequence analysis provide a useful base for their genetic manipulation and functional analysis.