Transcriptome Analysis of Heterosis for Young Spikes in Sorghum Hybrid and Its Parents

Background: Heterosis has been widely used for breeding high-yield crops, changes crop breeding and agricultural production by increasing yield. Transcriptome profiles of sorghum spikes in hybrid Jinnuo 3 and its parents 10480A and L17R were performed by RNA sequencing technology at secondary branch and spikelet differentiation period. Results During above two differentiation period, there were 2,641 and 2,175 differentially expressed genes (DEGs) between Jinnuo 3 and 10480A, respectively. Meanwhile, there were 1,387 and 1,094 DEGs between Jinnuo 3 and L17R, respectively. These indicated that massive DEGs were existed between hybird and its parents, and a more similar expression pattern was presented between hybrid and male parent. Gene expression inheritance analysis showed that most of genes were expressed additively, suggesting that the complementary effect may play a foundation role in sorghum spike heterosis. Among non-additive expression genes, L17R-dominant genes were predominant, indicating that male parent may provide beneficial alleles with great contribution to heterosis. GO and KEGG analysis suggested that metabolic pathways, such as photosynthetic antenna protein, photosynthesis, carbon fixation in photosynthetic organisms, amino acid metabolism, glycolysis, and endoplasmic reticulum protein processing, would participate in yield heterosis formation in hybrid Jinnuo 3. Further analysis showed that photosynthesis-related genes PsbW, PsbR, Lhca2, Lhcb1 and LAX3, spike structure development-related genes MADS1, MADS7, MADS16 and MADS55, as well as stress resistance-related genes WRKY14, WRKY35, HSFB2C and HSP70, might play an important role in yield heterosis formation in hybrid Jinnuo 3. Conclusion Hybrids Jinnuo 3 increased yield by simultaneously increasing source (photosynthetic efficiency-related genes), library (spike development-related genes), and resistance (inresistance-related genes). This molecular mechanism could provide new clues for sorghum heterosis utilization and high-yield breeding.