Over-expression of SlWRKY39 leads to enhanced resistance to multiple stress factors in tomato

The WRKY transcription factors are one of the well-characterized classes of plant transcription factors, which participated in various biotic and abiotc stress responses. Previous study showed that there are 81 WRKY genes in tomato, wherein a number of SlWRKY genes including SlWRKY39 were significantly up-regulated under salt, drought stress and PstDC3000 infection. However little is known about their physiological role in tomato. In this study, by using a forward genetic approach, we demonstrated transgenic plants over-expressing SlWRKY39 showing enhanced resistance to multiple stress factors including PstDC3000, salt and drought. Transgenic plants accumulated higher level of proline and lower level of malonic dialdehyde. Compared with wild type, the expression of pathogenesis-related genes SlPR1, SlPR1a1 and environmental stress related genes SlRD22, SlDREB2A were up-regulated in the transgenic plants. These results indicated that SlWRKY39 is a positive regulatory component of tomato against biotic and abiotic stress probably via activating the expression of both pathogenesis-related genes and stress related genes.