SlCV affects starch metabolism by regulating SlBAM3 stability under low night temperature stress in tomatoes.

Nocturnal starch remobilization is critical for plant carbon allocation and stress adaptation. While β-amylase 3 (BAM3) serves as the primary catalyst for starch degradation at night, its regulation mechanisms under stress remain to be fully characterized. The chloroplast vesiculation (CV) protein is crucial for maintaining chloroplast homeostasis during stress conditions, though its potential involvement in starch metabolic processes remains unexplored. Herein, we show that low night temperature (LNT) stress induces starch accumulation in tomato leaves, with SlCV overexpression exacerbating this phenotype and compromising LNT tolerance, whereas SlCV silencing promotes starch catabolism. RNA-seq and metabolome analyses detected lower levels of starch metabolites and amylase activity in SlCV overexpression plants. Strikingly, we have confirmed the physical interaction between SlCV and SlBAM3, and SlCV overexpression significantly accelerated the degradation of SlBAM3 under LNT stress, while SlCV knockout enhanced the stability of SlBAM3. Genetic validation confirmed that SlBAM3-silenced plants accumulate excessive starch and exhibit LNT-sensitive phenotypes, and SlBAM3 overexpression enhances cold tolerance. Furthermore, SlBAM3 complementation rescues the starch overaccumulation and LNT hypersensitivity of SlCV overexpression plants. These results elucidate the regulatory mechanism of starch metabolism mediated by SlCV and associated with SlBAM3 protein stability, providing novel insights into the starch metabolic pathway under cold stress.