VmUGT89AK4-mediated plant root resistance via regulating salicylic acid metabolism in tung trees

Plants have evolved intricate defense mechanisms to combat pathogens infection. Maintaining a stable basal level of salicylic acid (SA) is crucial for plant growth and pathogens response, although basal levels of SA vary significantly among plant species. The SA and its sugar conjugates play important roles in maintaining SA metabolism. Vernicia , known as the tung oil tree, suffers from disease caused by F. oxysporum f. sp. f ordiis ( Fof- 1), while its sister species Vernicia montana displays high resistance to Fof- 1. Transcriptomic and metabolism analysis led to the discovery of four SA glycosyltransferase, including Vmo026507, Vmo021696 ( VmUGT89AK4 ), Vmo018173, and Vmo003207 in V. montana . Here, based on the correlation coefficient (Pearson r) analysis between the accumulation of SA metabolites and transcription levels of 4 VmUGTs . The VmUGT89AK4 had highly significant correlation with root SAG (SA-glucoside) content expression. Enzyme activity assays revealed that VmUGT89AK4 exhibited catalytic activity on SA of substrates in vitro, form SAG. Transgenic tung tree overexpression VmUGT89AK4 exhibited greater susceptibility to Fof- 1 infection compared with EV plants, with OE- VmUGT89AK4 root accumulating significantly less SA level, and accompanied by reduced expression of pathogen-related genes after Fof- 1 infection. VmUGT89AK4 -silenced tung tree exhibited greater resistance to Fof- 1 infection than EV plants, and accumulated more SA and reduce SAG accumulation. These results suggest that VmUGT89AK4 is a SA glucosyltransferase that plays a negative regulatory factor by modulating SAG formation in tung tree. Our findings reveal the role of VmUGT89AK4 in SAG formation and regulation of plant defense. While also shedding light on the role of a new subfamily SA glycosyltransferase (UGT89s), which offered a new progress into the resistance response of tung trees. Schematic representation the roles of VmUGT89AK4 function in fine-tuning the SA levels and coordinated plant resistance to Fof- 1. • The VmUGT89AK4 had highly significant correlation with root SAG content expression • VmUGT89AK4 exhibited catalytic activity on SA, form SAG. • OE- VmUGT89AK4 exhibited greater susceptibility to Fof- 1 infection, with root accumulating significantly less SA level. • VmUGT89AK4 -silenced tung tree exhibited greater resistance to Fof- 1 infection, and accumulated more SA and reduce SAG accumulation. • VmUGT89AK4 is a SA glucosyltransferase that plays a negative role in Fof- 1resistance.