Transcriptome profiling of Sorghum bicolor reveals cultivar-specific molecular signatures associated with starch and phenolic compounds biosyntheses and accumulation during sorghum grain development

Sorghum is an important crop, and starch and phenolic compounds are major and important components in the sorghum grain. However, the underlying critical genetic elements contributing to the rich portfolio of nutrients in sorghum grains are largely unknown. Transcriptomic methods were employed to characterize the expression patterns at five different grain developmental stages of Hongyingzi (an important brewing sorghum), and another two grain sorghums, Jinuoliang 1 and Hongliangfeng 1, for comparison. The uniquely expressed genes were identified at each developmental stage of Hongyingzi when compared with the other two sorghum cultivars. The co-regulated genes at different developmental stages and the regulatory network were determined; the determinant genes and single-nucleotide polymorphisms located at the promoters of these genes involved in starch and phenolic compounds biosynthetic pathways were also identified. These results will provide insights into the potential regulatory network and further contribute to the clarification of the key determinant genes involved in the biosyntheses of starch and phenolic compounds. Meanwhile, some new transcripts and genes were identified at five different developmental stages of grains of the three sorghum cultivars. Our work can provide impetus for further study of the genes responsible for the biosynthesis of starch and phenolic compounds in the sorghum grain, and pave a way for functional validation of a batch of potential genes and single-nucleotide polymorphisms proposed in current work.