STP2-mediated sugar transport in tomato shoot apices is critical for CLV3 arabinosylation and fruit locule development under low temperatures.

Abstract

Prolonged exposure to low temperatures during agricultural production often leads to fruit malformation in crops, significantly reducing market value. However, the underlying molecular mechanisms remain poorly understood. In this study, we identify sugar transport protein 2 (STP2) as a critical regulator of tomato fruit locule development under cold conditions. Low temperatures impair long-distance sucrose transport from leaves to shoot apices, resulting in reduced accumulation of glucose and arabinose. In response, STP2 expression is strongly upregulated in shoot apices, promoting glucose and arabinose transport. We found that the CLAVAT3-WUSCHEL (CLV3-WUS) regulatory module, which governs locule formation, relies on STP2-mediated sugar transport for CLV3 arabinosylation. Overexpression of STP2 promotes glucose and arabinose accumulation in shoot apices, enhances CLV3 arabinosylation and the WUS suppression, mitigating the multi-locular malformations induced by low temperatures. Conversely, disruption of STP2 function exacerbates locule number increases under low temperatures, which could not be rescued by exogenous sugar supplementation. Our findings reveal a key mechanism by which STP2-mediated sugar transport supports CLV3 arabinosylation to maintain fruit locule development under low temperatures, offering potential strategies to alleviate fruit malformations in winter crop cultivation.