HuGAI1: a key transcription factor upregulated by trypsin, regulating phenylpropanoid biosynthesis, and enhancing fruit shelf life in Hylocereus undatus.

DELLA proteins can participate in the biosynthesis pathway of flavonoids. It has been shown that trypsin can induce flavonoid synthesis, thereby enhancing the storage quality of Hylocereus undatus (H. undatus ) fruit. However, whether trypsin induces flavonoid biosynthesis and improves fruit quality during storage by regulating the phenylpropanoid synthesis pathway through DELLA remains to be further elucidated. To investigate the molecular mechanism of trypsin-induced flavonoid synthesis in H. undatus , we conducted transcriptomic analysis and verified it through virus-induced gene silencing (VIGS). Analysis of transcription factors showed that the top five genes with the largest expression differences regulated by trypsin all belonged to the GRAS family. Further protein network interaction analysis identified HuGAI1 as a hub protein in the GRAS family. Trypsin treatment was able to extend the shelf life of fruit. However, after the expression of HuGAI1 was silenced, the storage quality of the fruit declined. GO and KEGG analysis after HuGAI1 silencing revealed that differentially expressed genes (DEGs) were mainly concentrated in metabolic pathways such as phenylpropanoid, flavonoid, and flavonol biosynthesis. Trypsin can upregulate the expression of HuGAI1 . And HuGAI1 , by participating in the phenylpropanoid biosynthesis pathway, regulates the biosynthesis of flavonoids and flavonols, leading to an increase in antioxidant flavonoid content and, consequently, enhancing fruit storage.