Methionine sulfoxide reductase B5 plays vital roles in tomato fruit defense response against Botrytis cinerea induced by methyl jasmonate

Abstract

A methionine sulfoxide reductase (Msr) gene is identified in tomato fruit, and its protein’s identity as MsrB5 was determined by phylogenetic analysis and multiple sequence alignment. Correspondingly, the role of SlMsrB5 in methyl jasmonate (MeJA)-mediated defense to B. cinerea in tomato fruit was investigated by using 0.05 mM MeJA treatment on SlMsrB5-silenced fruit during storage. The results showed that MeJA treatment upregulated total phenols and flavonoids, disease resistance enzymes activities, and expression of pathogenesis-related (PR) genes, including SlPR1/2a/2b/3a/3b/STH2 in tomato fruit. Additionally, MeJA inhibited the increase of hydrogen peroxide and superoxide anions by improving antioxidant enzyme activities and the ascorbic acid-glutathione (ASA-GSH) cycle. Similarly, MeJA induced the accumulation of jasmonic acid and the transcriptions of its signal transduction-related genes (SlCOI1 and SlMYC2), which could lead to the transcription of disease response-related marker genes such as SlPI I and SlPI II. These MeJA-regulated changes may contribute to improved disease resistance in tomato fruit. However, SlMsrB5 silence reduced the effect of MeJA on the above parameters and caused severer disease occurrence in the SlMsrB5-silenced + MeJA treated group than in MeJA treated group, probably because the low levels of SlMsrB5 transcription could not restore the activity of defense and antioxidant-related enzymes. Furthermore, correlation analysis revealed that the above effects regulated by MeJA were highly correlated with SlMsrB5 transcript levels. Therefore, these findings provide insight on SlMsrB5's role in MeJA-mediated tomato immune responses to B. cinerea by regulating defensive enzymes and genes, antioxidant capacity, and the JA signaling pathway.