Abstract
In plants, vesicular trafficking is crucial for the response and survival to environmental challenges. The active trafficking of vesicles is essential to maintain cell homeostasis during salt stress. Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are regulatory proteins of vesicular trafficking. They mediate membrane fusion and guarantee cargo delivery to the correct cellular compartments. SNAREs from the Qbc subfamily are the best-characterized plasma membrane SNAREs, where they control exocytosis during cell division and defense response. The Solanum lycopersicum gene SlSNAP33.2 encodes a Qbc-SNARE protein and is induced under salt stress conditions. SlSNAP33.2 localizes on the plasma membrane of root cells of Arabidopsis thaliana. In order to study its role in endocytosis and salt stress response, we overexpressed the SlSNAP33.2 cDNA in a tomato cultivar. Constitutive overexpression promoted endocytosis along with the accumulation of sodium (Na+) in the vacuoles. It also protected the plant from cell damage by decreasing the accumulation of hydrogen peroxide (H2O2) in the cytoplasm of stressed root cells. Subsequently, the higher level of SlSNAP33.2 conferred tolerance to salt stress in tomato plants. The analysis of physiological and biochemical parameters such as relative water content, the efficiency of the photosystem II, performance index, chlorophyll, and MDA contents showed that tomato plants overexpressing SlSNAP33.2 displayed a better performance under salt stress than wild type plants. These results reveal a role for SlSNAP33.2 in the endocytosis pathway involved in plant response to salt stress. This research shows that SlSNAP33.2 can be an effective tool for the genetic improvement of crop plants.
Highlights
In eukaryotic cells, a vesicular trafficking system allows communication between their internal compartments and neighboring cells
Characterized A. thaliana plants expressing fluorescent genetic markers specific for Golgi, Trans Golgi network, Late endosome, tonoplast, and plasma membrane, respectively, were used to identify the subcellular location of SlSNAP33.2::GFP [28]. Root cells from those plants were transiently transformed with pSlSNAP33.2::GFP using AGROBEST technique [29], and the transformed cells were analyzed under the confocal microscope
SlSNAP33.2::GFP did not localize at the Golgi complex, and no overlap was observed between the GFP and mCherry signals in cells expressing the Golgi-localized probe AtSYP32-mCherry
Summary
A vesicular trafficking system allows communication between their internal compartments and neighboring cells. Membrane fusion is possible with a SNARE complex formed by only three proteins instead of four. This occurs when a Q-SNARE has two SNARE domains in its polypeptide chain, as is the case for the Qbc-SNAREs. This occurs when a Q-SNARE has two SNARE domains in its polypeptide chain, as is the case for the Qbc-SNAREs One of them is the Synaptosome-associated protein 25 (SNAP25) involved in the fusion of vesicles with the plasma membrane. Another structural feature unique to Qbc-SNAREs is their integration into the membrane; while most SNAREs display a transmembrane domain, SNAP25-type proteins are attached to the membrane by a lipidic group added by posttranslational modification [7], further suggesting important differences in the molecular mechanism of Qbc-SNAREs-mediated membrane fusion compared to other SNARES
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