Transcriptome Analysis Reveals the Accumulation Mechanism of Starch in Chinese Yam (Dioscorea opposite Thunb.) Tubers Using RNA-Seq and Iso-Seq

Abstract

The starch composition of tubers affects the quality and yield of yam, and it is of great significance to deeply investigate the mechanism of starch accumulation in yam. In this study, two yam varieties with significant differences in starch content, Bikeqi (Dioscorea opposita Bikeqi) and Dahechangyv (Dioscorea opposita Dahechangyu), were used as materials. The transcriptome of tubers from seven developmental stages were sequenced using RNA-seq and Iso-seq. Differential genes closely contacted with the metabolism of starch and sucrose were screened and the functions were analysed. The results showed that, the starch content of the two yam varieties reached the maximum at 150 and 165 days respectively, and their difference was the largest at 150 days. Total 21623 unigenes were annotated, and 8378 differential genes were identified within varieties by comparing each developmental stage with the beginning of tuber expansion (90 days), respectively. A total of 5177 differential genes were identified in two varieties in the same period. GO and KEGG were used to analyze these differential genes, a variety of key genes closely related to starch and sucrose metabolism were screened. These results help us to better understand the mechanism of starch accumulation in yam.