Response Of The Arabidopsis SYTA To Salt Stress

Synaptotagmin,one kind of putative Ca²⁺ sensors, regulated Ca²⁺–dependent synaptic vesicle membrane fusion in animal cells. Synaptotagmins are a family of membrane-trafficking proteins that are made by an N-terminal transmembrane region, a linker of variable size, and two C-terminal C2 domains in tandem. The Arabidopsis genome contains five genes encoding synaptotagmin-like proteins. In Arabidopsis, SYTA is required for the maintenance of plasma membrane integrity and cell viability, and regulates endocytosis and virus movement protein cell-to-cell transport.Arabidopsis synaptotagmin A is required for the maintenance of plasma membrane integrity and cell viability in response to salt stress. The homozygous T-DNA mutants and over-expression of the SYTA gene in Arabidopsis were used to observe SYTA gene expression, calcium regulation and role in the pathway of the salt stress. The results are shown as follows:1. Analysis of SYTA gene expressionThe Semi-Quantitative RT-PCR was used for the analysis of the expression levels of SYTA gene under salt stress. The expression profiling showed that SYTA was highly expressed under salt stress,and the expression of SYTA gene was significantly up- regulated with salt concentration increasing.2. Salt stress sensitivity analysis of SYTA genePhenotype analysis suggested that the seed root elongation of the mutant was more sensitive to salt stress, while that of the over-expression was more salt tolerant than the wild type. The results showed that AtSYTA gene may play an important role in the plant response to salt stress.3. Sensitivity analysis of exogenous calcium of SYTA geneResearch also found that the expression of SYTA was activated by low level exogenous calcium. Analysis of relevant phenotype revealed that the inhibition on seed root elongation of SYTA mutant and over-expression transgenic lines by salt stress have been alleviated by calcium,and the effect on that of the over-expression was the most obvious. This again confirms the fact that SYTA gene is adjusted by calcium signaling.4. Determination of related index under salt stressFinally, determination of related physiological indexes of SYTA mutant and over-expression transgenic lines found that over-expression transgenic lines were more salt tolerant in photosynthetic index, Na⁺ accumulation and relative electric conductivity under salt stress.All of the above results showed that SYTA played an important adjustment action in signal transduction in Arabidopsis salt stress response.