Molecular Characterization and Functional Analysis of the Receptor-like Kinase SOBIR1 on Tomato Plants Infected By a Potyvirus

The exposure of plants to various biotic and abiotic stresses interferes with the expression patterns of several host genes. Research on differential gene expression in tomato plants infected with Pepper yellow mosaic virus (PepYMV) revealed a down-regulation of a gene encoding a leucine-rich repeat receptor-like kinase (LRR-RLK). LRR-RLKs constitute a diverse group of proteins allowing the cell to recognize and respond to the extracellular environment, being a component of the signal transduction pathway. The present work aimed to perform a molecular and functional characterization of the gene encoding such LRR-RLK from tomato (Solanum lycopersicum) (SlSOBIR1), in order to unravel a possible implication of this receptor in triggering defense responses during viral infection. Molecular characterization of SlSOBIR1 was acquired through the determination of its expression profile in response to PepYMV and to mechanical wounding employing real-time PCR. In functional analysis, the effect of the overexpression of SlSOBIR1 on viral infection as well as on the expression of selected defense genes was investigated. The results revealed that SlSOBIR1 is repressed during tomato infection with PepYMV and is responsive to mechanical wounding. Moreover, no differences in viral accumulation were observed between transgenic tobacco plants overexpressing SlSOBIR1 and untransformed plants (WT). An increase in PR1 and PR6 expression was evident in the SlSOBIR1 plants after injury but in a similar way to the one observed in WT. The data obtained so far provided us with important information about SlSOBIR1 and its product, however no direct proof of its involvement in viral infection was obtained.