Role of TgVIN1 and TgPEPCK in sugar/starch and lipid metabolism pathways in Torreya grandis seeds under foliar fertilizer treatments.

Foliar fertilizers quickly replenish nutrients for plant growth, boosting production and quality. However, how this affects metabolite accumulation in fruits is unclear. In this study, the metabolome and transcriptome of Torreya grandis seeds were investigated after five different foliar fertilizer treatments. Based on the results, foliar fertilizer treatments significantly altered the visual properties and nutritional quality of T. grandis seeds. According to the transcriptome and metabolome data, the differential metabolites and genes in T. grandis seeds were enriched in the sugar/starch and lipid metabolism-related pathways. Correlation analysis revealed that TgVIN1 and TgPEPCK play key roles in sugar/starch and lipid metabolism pathways, respectively. A dual-luciferase analysis and yeast one-hybrid assay were used to examine the regulation of candidate transcription factors on TgVIN1 and TgPEPCK expression. The results showed that TgHDZIP1 and TgMYB7 could directly bind to the TgVIN1 promoter and activate TgVIN1 expression. Similarly, TgIWS1 could directly bind to the TgPEPCK promoter. Transient overexpression of TgVIN1 increased the contents of fructose, soluble sugar and starch in and TgPEPCK significantly increased the C16:1 content in tobacco leaves, respectively. Our results contribute to the mechanisms underlying sucrose/starch and lipid metabolism as affected by foliar fertilizer treatments.