Functional Mechanism Of SIGR Gene On Tomato Fruit Ripening

Green-ripe (Gr) tomato carries a dominant mutation and yields a nonripening fruit phenotype. The mutation results from a334-bp deletion in the5’-flanking region of a functionally unknown gene at the Gr locus. However, the ectopic expression of SIGR in the Gr mutant does not alter the sequence of the protein-coding region. The putative influence of SIGR gene-deletion mutation on biochemical changes underlying the nonripening phenotype remains largely unknown. Here, we utilized high-throughput iTRAQ (Isobaric Tag for Relative and Absolute Quantification) combined with VIGS (Virus-induced Gene Silencing), and other complementary molecular and physiological techniques to try to uncover the regulation of SlGR in tomato fruit ripening. Main results are listed as follows:1. Expression profile of SlGR was detected in wild-type AC fruit and Gr mutant fruit, as well as Rin and Nr mutant fruit. Data showed that the over-expression of SIGR is conserved in Gr mutant fruit.2. Exogenous ethylene was used to treat with the wild-type fruit. It showed that SIGR can be induced by the ethylene, which means SIGR is involved in the ethylene-dependent signal pathway. Data showed that the transcript of tomato SIACO1, SICTR1, SIEIN2and SIEIL1were influenced significantly by SIGR expression, and SICTR1and SIEIN2can both influence the expression of SIGR gene significantly. All these investigations showed that SIGR is involved in fruit ethylene signaling and feedback.3. The yeast library was screened to find out the interactive proteins with SIGR. Totally,70proteins showed putative interaction with SIGR. Upon the information from previous work on SIGR, we choosed two protein kinase, SlILRR and SlSTPK, for further research. Data from yeast two hybrid showed that SlILRR and SlSTPK could interact with SIGR in vitro.4. High-throughput iTRAQ technology was utilized to identify differential proteins from breaker Gr mutant fruit compared with wild-type fruit. The proteomic data was integrated into a network containing several metabolic or regulatory pathways to gain a systematic and broader elucidation of processes in the Gr mutant fruit.5. The transcript level of all differentially displyed proteins was also tested. A novel relation among the ectopic expression of SIGR, metabolic characteristics, and nonripening phenotype of Gr fruit was showed. And the putative influence of SIGR on all these metabolic characteristics was verified by the silencing of SIGR.Together, our research work help to uncover the biological mechanism of tomato SIGR on fruit ripening, and provid evidence for the hypothesis that there exists a distinct ethylene signaling modules in tomato mediated by SIGR.