Differential expression and localization of expansins in Arabidopsis shoots: implications for cell wall dynamics and drought tolerance

Expansins are cell wall-modifying proteins implicated in plant growth and stress responses. In this study, we explored the differential localization of expansins in <i>Arabidopsis thaliana</i> shoots, with a focus on <i>EXPA1, EXPA10, EXPA14</i>, and <i>EXPA15</i> utilizing <i>pEXPA::EXPA</i> translational fusion lines. Employing the chemically inducible system pOp6/LhGR for <i>EXPA1</i> overexpression and high-throughput automatic phenotyping we evaluated the drought response and photosynthetic efficiency under stress conditions. We observed distinct expression patterns of expansins, with <i>EXPA1</i> primarily localized in stomatal guard cells, while <i>EXPA10</i> and <i>EXPA15</i> showed strong cell wall (CW) localization in epidermal and other tissues. Overexpression of <i>EXPA1</i> resulted in pronounced changes in CW-related gene expression, particularly during early stages of induction, including the upregulation of other expansins and CW-modifying enzymes. The induced <i>EXPA1</i> line also displayed significant morphological changes in shoots, including smaller plant size, delayed senescence, and structural alterations in vascular tissues. Additionally, <i>EXPA1</i> overexpression conferred drought tolerance, as evidenced by enhanced photosynthetic efficiency (F_v/F_M), and low steady-state non-photochemical quenching (NPQ) values under drought stress. These findings highlight the critical role of <i>EXPA1</i> in regulating plant growth, development, and stress response, with potential applications in improving drought tolerance in crops.