The Exocytosis Associated SNAP25-Type Protein, SlSNAP33, Increases Salt Stress Tolerance by Modulating Endocytosis in Tomato

• Main Authors: Josselyn Salinas-Cornejo, José Madrid-Espinoza, Isabel Verdugo, Jorge Pérez-Díaz, Alex San Martín-Davison, Lorena Norambuena, Simón Ruiz-Lara
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: Plants
• Subjects: SNARE; SNAP33; <i>S. lycopersicum</i>; endocytosis; salt stress; sodium compartmentalization
• Online Access: https://www.mdpi.com/2223-7747/10/7/1322

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 <i>Solanum lycopersicum</i> gene <i>SlSNAP33.2</i> encodes a Qbc-SNARE protein and is induced under salt stress conditions. <i>Sl</i>SNAP33.2 localizes on the plasma membrane of root cells of <i>Arabidopsis thaliana</i>. In order to study its role in endocytosis and salt stress response, we overexpressed the <i>SlSNAP33.2</i> 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 <i>SlSNAP33.2</i> 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 <i>SlSNAP33.2</i> displayed a better performance under salt stress than wild type plants. These results reveal a role for <i>Sl</i>SNAP33.2 in the endocytosis pathway involved in plant response to salt stress. This research shows that <i>SlSNAP33.2</i> can be an effective tool for the genetic improvement of crop plants.