Characterization and functional analysis of methionine sulfoxide reductase A gene family in tomato.

In this study, four methionine sulfoxide reductase A (MSRA) genes, SlMSRA2-5, were identified in Micro-Tom (Solanum lycopersicum cv.'Micro-Tom') based on the tomato database. Exon/intron distribution assays indicated that the gene sequence of SlMSRA2, SlMSRA3, and SlMSRA4 contained two exons and one intron in the tomato genome, while the coding sequence of SlMSRA5 was interrupted by three introns. Southern blot analysis revealed that the members of the MSRA family existed as low copies in the tomato genome. Although SlMSRA2 and E4 gene (one of ethylene-inducible gene) share a similarity of 93.4% in terms of their amino acid sequence, organ-specific expression revealed that gene expression were remarkably different based on Northern blot analysis. In addition, SlMSRA3 and SlMSRA4 transcripts were abundant in leaves while expression of SlMSRA5 was weak in most of organs examined. The expression pattern of SlMSRAs induced in response to hormones and stresses suggested that the tomato MSRA genes might be involved in resistance against pathogens and various abiotic stresses. In addition, kinetics parameters suggested that recombinant SlMSRA4 protein exhibited a highest affinity for dabsyl-labeled methionine sulfoxide and its catalytic efficiency (K (cat) /K (m) ) was threefold and 6.5-fold higher than that of SlMSRA2 and SlMSRA3. However, the activity of purified SlMSRA5 was not detected in the DTT-dependent reducing system.