The Effect of Ethylene on Squalene and Β-Sitosterol Biosynthesis and Its Key Gene Network Analysis in Torreya Grandis Nuts During Post-Ripening Process

Squalene and β-sitosterol are health-benefit compounds due to their nutritional and medicinal properties. It has been reported that the content of these bioactive compounds is relatively high in Torreya grandis nuts. However, it is not yet known what changes in squalene and β-sitosterol accumulation occur during the special post-ripening process of T. grandis nuts and the effect of the well-known ripening hormone ethylene on the regulatory mechanism of their biosynthetic pathways. Thus, we performed transcriptome and metabolite analyses. The results showed that ethylene not only promoted the post-ripening process but also enhanced the accumulation of squalene by inducing gene expression in the mevalonate pathway. At the same time, ethylene treatment also promoted the accumulation of other sterols but inhibited gene expression in the β-sitosterol biosynthesis pathway. In addition, co-expression and correlation analysis suggested a framework for the transcriptional regulation of squalene and β-sitosterol biosynthesis genes under ethylene treatment.