SaUGTs regulate YE-induced phytoalexins homeostasis in Sorbus aucuparia suspension cells

Glycosyltransferases (GTs) are key post-biosynthetic enzymes that catalyze the formation of glycosidic bonds in secondary metabolites, playing a critical regulatory role in plant cellular metabolic homeostasis. Biphenyl, dibenzofuran, and their glycosides, the most abundant phytoalexins in the apple subfamily, are synthesized de novo after infection by bacteria or fungi. Nevertheless, the biological functions of GTs in Sorbus aucuparia remain largely unexplored.

This study aims to investigate the regulatory roles of Sorbus aucuparia uridine diphosphate glycosyltransferases (SaUGTs) in biphenyl phytoalexin metabolism and cellular growth dynamics in suspension-cultured cells (SASCs) under yeast extract (YE)-induced stress.

A standardized SASC culture system was established and treated with YE stress. A multi-omics approach was employed, integrating phenotypic analysis, targeted metabolomics, transcript profiling, and in vitro enzyme assays.

YE treatment led to a transient reduction in biomass alongside a marked accumulation of biphenyl aglycones and glycosides. Temporal metabolite profiling indicated dynamic shifts corresponding to sequential biosynthetic events. Soluble protein content and SaUGTs transcript levels were significantly elevated. Functional assays confirmed that YE-induced SaUGTs catalyze the glycosylation of noraucuparin, aucuparin, and 2'-hydroxyaucuparin. Optimal cell proliferation was observed when metabolic equilibrium was maintained between aglycones and glycosides.

These results reveal a previously unrecognized regulatory mechanism, wherein SaUGTs-mediated glycosylation modulates biphenyl phytoalexin homeostasis, enabling SASCs to balance defense activation and growth under YE elicitor stress.