Role in defense of the two glycosyltranferases UGT74F1 and UGT74F2 against Pseudomonas syringae

Abstract: Glucosyltransferases UGT74F1 and UGT74F2 are the major responsible for the synthesis of the salicylic acid (SA) conjugates glucosyl salicylate (SAG) and salicylic glucosyl ester (SGE). The relation of these two genes and plant defense against Pseudomonas syringae DC3000 (Pst) is investigated in this work. The mutants ugt74f1 and ugt74f2, altered in the corresponding glucosyltransferases were affected in their basal resistance against Pst. ugt74f1 showed enhanced susceptibility visible as more pronounced disease symptoms, while ugt74f2 showed enhanced resistance against the same pathogen. Both mutants have to some extent, altered levels of SAG and SGE compared to wild type plants, however, in response to the infection, ugt74f2 accumulated higher levels of free SA at 24 hpi compared to wild type plants while ugt74f1 accumulated lower SA levels. These results suggest that UGT74F2 negatively influences the accumulation of free SA, hence leading to an increased susceptibility due to reduced SA levels.