Background: Sesame (Sesamum indicum) can accumulate over 60% oil in its seed. However, low oil content genotypes with an oil content of less than 50% are also observed. To gain insights into how genes shape this variation, we examined 22 seed and carpel transcriptomes from 3 varieties of sesame with high and low oil content.
Results: A total of 34.6~52.2% of the sesame genes were expressed with a RPKM greater than 5 in the 22 tissue samples. The expressed gene numbers tended to decrease in the seed but fluctuated in the carpels from 10 to 30 days post-anthesis (DPA). Compared with that of the low oil content sesames, the high oil content sesame exhibited more positive gene expression during seed development. Typically, genes involved in lipid biosynthesis were enriched and could distinguish the high and low genotypes at 30 DPA, suggesting the pivotal role of seed oil biosynthesis in the later stages. Key homologous lipid genes that function in TAG biosynthesis, including those that encoded glycerol-3-phosphate acyltransferase (GPAT), acyl-CoA:diacylglycerol acyltransferase (DGAT), and phospholipid:diacylglycerol acyltransferase (PDAT), were strengthened asynchronously at different stages, but the lipid transfer protein (LTP)-encoding genes, including SIN_1019175, SIN_1019172 and SIN_1010009, usually were highlighted in the high oil content sesames. Furthermore, a list of 23 candidate genes was identified and predicted to be beneficial for higher oil content accumulation. Despite the different gene expression patterns between the seeds and carpels, the two tissues showed a cooperative relationship during seed development, and biological processes, such as transport, catabolic process and small molecule metabolic process, changed synchronously.
Conclusions: The study elucidated the different expression profiles in high and low oil content sesames and revealed key stages and a list of candidate genes that shaped oil content variation. These findings will accelerate dissection of the genetic mechanism of sesame oil biosynthesis.
Keywords: Carpel; Expression profiling; Gene; Oil content; Seed; Sesamum indicum.