Cloning And Functional Research Of Tomato SR/CAMTA Family Gene SlSR4

SR/CAMTA family proteins are widespread transcription factors in eukaryotes, which have been found to play an important role in the process of growth and development. The SR/CAMTA proteins consist of multiple predicted functional domains, and organized in a conserved order. All SR/CAMTAs share a novel type of sequence-specific DNA-binding domain,which are designated CG-1. The DNA-binding domain could bind DNA directly and activate transcription, but also interact with other transcription factors and as a co-activator of transcription. SR/CAMTAs have been investigated to play a broad range of functions from mediate of responses to external stimuli, growth control, cardiac growth, tumor suppression and memory performance. Seven SR/CAMTAs genes were identified in tomato,but their functions were not very clear. This study selected SlSR4 gene as the research object, which had the lower homologous with other 6 SR/CAMTAs genes, and carried on the further research work.We found that the expression of SlSR4 gene was universal in different tissues of Mill.cv.Ailsa Craig(AC++) tomato by Real-time PCR analysis,in which Fl(flower)was the highest and fruit periods expressed relatively lower. In addition, SlSR4 gene was also expressed at different degree in mutant Nr, Rin fruit.We analyzed the expression level of SlSR4 gene under dehydration, injury, cold, salt stress by Real-time PCR technology. The results implyed that the expression of SlSR4 gene were induced at different degree by the four treatments, but the response to salt treatment was more obvious. This indicated that SlSR4 gene is likely to play an important role in these signaling pathways.We analyzed the expression level of SlSR4 gene under GA, ABA, ACC, MeJA, IAA and SA hormone treatments by Real-time PCR technology. The results implyed that the SlSR4 gene was not sensitive to ABA treatment, a slight response to ACC and Meja, and obvious response to GA, IAA and SA.The RNAi silencing vector of SlSR4 gene was conducted and transfered into the wild type tomato cotyledon explant via Agrobacterium-mediated transformation, and obtained transgenic tomato lines with better silencing efficiency in leaves. We analyzed the expression level of cell wall metabolism related genes of fruit by Real-time PCR technology. We found that the expression of PG, PE1 and CEL were upregulated in B+4 fruits of transgenic lines, and decreased tomato fruit storability. In addition, the silencing efficiency of SlSR4 gene in fruit was much less than leaf.The salt stress experiment was implemented in T1 generation of transgenic tomato seedlings. The results showed that the silence of SlSR4 gene impacted seedling hypocotyl growth, reduced tolerance to salt stress, and inhibited the expression of stress-related genes.We analyzed the expression level of other 6 SR/CAMTAs family genes in transgenic tomato seedlings. The results showed that the expression of SlSR2、SlSR2L、SlSR3 and SlSR3 L were slightly up-regulated in B+4 fruits of transgenic lines, while the expression of 6 SR/CAMTAs were downregulated at different degree in T1 generation of transgenic tomato seedlings under salt stress experiment. These results indicated that SlSR4 gene has certain influence on other SR/CAMTAs family genes, and the degree of influence is not the same between fruits and leaves.In summary, this study focus on analyzing the functions of SlSR4 gene in tomato,which provided a set of theoretical basis for cultivating the storability and salt tolerance of tomato plants.