Alterations in the proteomic profiles of Arabidopsis roots triggered by sodium chloride stress are exacerbated by impaired function of SYNAPTOTAGMIN 1.

Plant synaptotagmins, especially SYT1, are involved in responses to different environmental stressors. We revealed that SYT1 abundance at the cell periphery in Arabidopsis roots and its turnover decelerated upon salt stress. Results of proteomic analysis of the Arabidopsis syt1-2 allele demonstrated that under salt stress, more proteins accumulated and were depleted in the mutant than in the wild-type seedlings' roots. In both genotypes, these were mostly proteins hitherto unknown to be affected by salt stress. Proteins associated with the cytoskeleton, water deprivation, proteasome activity, oxidative stress, glutathione, lipid transfer, and glucosinolates were the most affected. When we analyzed the consequence of the mutation, 10 proteins were differentially abundant in mutant versus wild type in standard conditions, and 24 proteins under sodium chloride stress. Since these were relatively small numbers, syt1-2 was subjected to thorough molecular analysis. Results indicated that the altered SYT1 transcript was produced in syt1-2 with 75% reduced abundance compared to the unchanged transcript in the wild type.