Cloning expression analysis and functions of SIP1 subfamily gene(SlGT-33) in tomato Trihelix family

【Objective】Cloning expression and function of SIP1 subfamily gene(SlGT-33) of tomato Trihelix family to provide theoretical basis for analyzing the mechanism of SIP1 subfamily members regulating plant growth and development, and breeding of dwarf tomato varieties.【Method】Using the tomato variety AC⁺⁺, amplified its SlGT-33 gene by PCR, performed sequence analysis, and used real-time fluorescence quantitative PCR(qRT-PCR) to detect its expression patterns in different tissues and exogenous hormones and non-biological stress. Finally, the RNAi technique was used to identify the biological function of SlGT-33 gene.【Result】The length of SlGT-33(GenBank accession number:Solyc12g 043090) open reading frame(ORF) was 1125 bp, encoding 375 amino acids residues, which was short of 3 bp than its homologous gene(GenBank accession number:XP004252336.1). Phylogenetic analysis suggested that SlGT-33 protein was in the same branch with SlGT-17(GenBank accession number:Solyc05g018350), though the similarity between their amino acids sequence was the highest, the value was only 45.8%. SlGT-33 gene was significantly expressed in stem and mature leaves than other tissues(P<0.05, the same below). After IAA, GA₃, MeJA treatments, the expression of SlGT-33 gene did not differ significantly from control(P>0.05, the same below). Compared to control, SlGT-33 could be significantly up-regulated by ABA within 2-24 h. SlGT-33 gene expression was not significantly different from control under high salt stress and mechanical damage. The expression of SlGT-33 gene decreased gradually under high temperature stress and low temperature stress, while expression of SlGT-33 gene increased gradually under dehydrationstress. Six SlGT-33-RNAi silent lines were harvested by Agrobacterium-mediated transformation and silence rate varied from 64%to 83%. The plant height and internode length of 70 d SlGT-33-RNAi silent lines decreased to 60% of wild types. The compound leaf structure was significantly smaller and the inflorescence formed in advance. The key transcription factor genes KNOX2 and WUS in stem tip tissue were extremely significantly expressed in the SlGT-33-RNAi silent lines(P<0.01) or significantly higher than the wild type. Adenylate isopentenyl transferase(key enzyme for CTK synthesis) encoded gene IPT2 and the stem tip growth point regulatory gene PHAN were expressed significantly lower in two SlGT-33-RNAi silent linesthan wild type. The expression of the apical biological tissue key transcription factor gene KNOX1 gene was not significantly different compared with in two SlGT-33-RNAi silentlines. Thecytokinin(CTK) of SlGT-33-RNAi silent line stem tip tissue was significantly lower than in the wildtype.【Conclusion】SlGT-33 gene was sensitive to environment. It can be induced by ABA and dehydration stresses and suppressed by extreme temperature. But suppressed expression of Sl-GT-33 leads to dwarf plants and accelerating reproductive development, which is related with inhibition of CTK synthesis of apical meristem and abnormal expressions of stem tip tissue key regulation genes KNOX2, PHAN and WUS.