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.