Development of Genome Resources and Their Utilization in Jatropha Through Comparative Genomics with Castor Bean

Abstract

Castor bean and Jatropha are seed oil plant species of immense industrial value and important sources of biodiesel. Taxonomical and biochemical similarities in both the species can be explored in transferring and utilizing the genome resources of one for the other. In this study simple sequences repeats (SSRs) were identified in the castor bean genome with a frequency of 1 SSR per 680 bp in genomic sequence. Distribution of SSRs in different regions of the genome showed that SSRs are more predominant in gene-rich regions of the genome. Dinucleotide repeats were the most frequent with (AT)n repeat motif in highest frequency. There was ~70% transferability of SSRs from castor bean to Jatropha with maximum for SSRs from exonic regions. The polymorphism was higher in SSRs from 5 UTRs with repeat length of 16-25 repeat units. Total of 302 SSRs, 211 were successfully transferred to Jatropha from castor bean genome. The study has provided a range of SSR markers, which can be tested and utilized in molecular breeding of castor bean and Jatropha alike. Fatty acid biosynthetic pathway is highly conserved in plants; but there are significant variations in fatty acid contents and composition in plants. Comparative gene structure analysis of fatty acid and TAG biosynthesis genes was perused in 4 plant species to correlate their sequence differences, if any, with the differences in the contents and composition of fatty acids in seed oil. Comparative gene structure analysis of 261 genes (68 from Arabidopsis, 62 from Brassica, 55 from castor bean and 76 from soybean) revealed the sequence variations (INDELs and SNPs) in ACCase, FatB, Stearoyl desaturase, FAD 2 and FAD 3 genes. Sequence variations identified in FatB gene will be helpful to enhance the content of saturated fatty acids, whereas variations in FAD2, FAD3 and Stearoyl desaturase genes will be helpful to enhance the content of unsaturated fatty acids in oil seed plant species.