Molecular cloning and functional characterisation of the tomato E3 ubiquitin ligase SlBAH1 gene

Emerging evidence suggests that E3 ligases play critical roles in diverse biological processes, including pathogen resistance in plants. In the present study, an ubiquitin ligase gene (SlBAH1) was cloned from a tomato plant, and the functions of the gene were studied. The SlBAH1 gene contained 1002 nucleotides and encodes a protein with 333 amino acids. The SlBAH1 protein contains a SPX domain and a RING domain. SlBAH1 displayed E3 ubiquitin ligase activity in vitro. SlBAH1 was shown to localise in the nucleus, cytoplasm and plasma membrane by a subcellular localisation assay. The expression of SlBAH1 was induced by various hormones and Botrytis cinerea Pers. treatment. SlBAH1-silencing in plants obtained by virus-induced gene silencing (VIGS) technology enhanced resistance to B. cinerea, and the expression of pathogenesis-related (PR) genes, including PR1, PR2, PR4, PR5, and PR7, was significantly increased. These results indicate that the SlBAH1-dependent activation of defence-related genes played a key role in the enhanced fungal resistance observed in the SlBAH1-silenced plants and may be related to the SA-dependent and JA-dependent signalling pathways.