Transcriptome Analysis Provides Insights into the Mechanisms of Starch Biosynthesis in the Kernels of Three Chestnut Cultivars

The chestnut is widely cultivated fruit tree enriched with nutrients and has pleasant tasting fruit. The starch properties of kernels greatly influence the nutritional quality of chestnuts. Although various studies have examined the production and accumulation of starch in chestnuts, the transcription alteration linked with starch properties in the kernels has not yet been fully assessed. The present study was conducted to compare transcriptomic variation and starch profiling of three chestnut cultivars: “Garrone rosso” (eur), Castanea sativa Mill., native to Europe; “Dahongpao” (dhp) and “Jiandingyouli” (jdy), and Castanea mollissima Bl., native to China. The results revealed that “dhp” and “jdy” had higher amylose, amylopectin and total starch content than “eur”. Based on transcriptome data, we screened 63.17G clean bases, and detected numerous differentially expressed genes (DEGs) that were associated with starch and sucrose metabolism. Through the combined transcriptomic and starch profiling analysis showed that DEGs in “the starch and sucrose metabolism”, “bZIP transcriptional factors”, and “zinc finger protein” pathways were positively correlated with starch accumulation, genes encoding sucrose synthase (CMHBY215664 and CMHBY203813), USPase (CMHBY206855), and PGI (CMHBY200699) were found to participate in the biosynthesis, transport, and regulation of starch according to their expression patterns in chestnut kernels. Furthermore, genes encoding different transcription factors (ERF, bZIP, MYB, and WRKY) that potentially regulate the expression of genes involved in starch and sucrose metabolism were selected by coexpression analysis, which highlighted that most MYB and WRKY TF members were positively correlated with starch synthase (SS). qRT-PCR assay results of nine selected DEGs confirmed the accuracy of the RNA-Seq data. Our results provide insights into genetic resources for deciphering the molecular mechanisms of chestnut starch accumulation.