Abstract
We clarified a novel regulatory mechanism of salicylic acid (SA) signaling by a model infection system using a combination of RCY1-overexpressed Arabidopsis and yellow strain of cucumber mosaic virus (CMV-Y). In this system, we can examine the RCY1-mediated extreme resistance (ER). The RCY1-overexpressed Arabidopsis were inoculated with CMV-Y by the carborundum method and kept for 10 min, 30 min, 1 h, 3 h, 6 h, 24 h, 36 h, 48 h and 72 h. Metabolites in the leaf samples were analyzed by ultra-performance liquid chromatography time-of-flight mass spectrometer (UPLC-TOF-MS). Principle component analysis of the metabolite data represented CMV-Y specific increase of several metabolites in comparison with the mock-induced metabolites. Significant changes of salicylic acid and its derivatives were observed in the CMV-Y inoculated leaves. Gene expression analysis showed CMV-Y specific repression of a salicylic acid glucosyltransferase gene UGT74F1 but not of salicylic acid biosynthesis and metabolizing genes. These results suggest that the suppression of SA glucosylation is a important regulatory step during RCY1-mediated resistance against CMV-Y.
