The interaction between CaDUF642.01 and CaPME2 influences stem strength in Capsicum annuum L.

Stem strength is a key agronomic trait that influences planting adaptability and mechanical harvesting efficiency. Pepper is the most widely cultivated vegetable crop in China, and full mechanization of its production is crucial for enhancing quality and productivity. In the preliminary stage of this study, transcriptomic analysis was performed on pepper accessions exhibiting substantial differences in stem strength at various developmental stages. Through weighted gene co-expression network analysis focused on genes involved in cell wall biosynthesis and transport, a candidate gene potentially regulating stem strength, designated CaDUF642.01, was identified. The CaDUF642.01 protein contains two DUF642 domains and localizes to the cell wall, plasma membrane, and nucleus. Silencing CaDUF642.01 led to a 42.17% decrease in soluble pectin content, a 1.63% reduction in water content, a 43.18% shortening of internode length, and more compact cell arrangement. Furthermore, CaDUF642.01 was shown to directly interact with pectin methylesterase 2 (CaPME2), forming a protein complex that modulates pectin methylation levels via regulation of random PME demethylesterification, thereby influencing stem strength. Our results demonstrate that the CaDUF642.01-CaPME2 complex attenuates stem strength by altering pectin composition through PME activity, which also increases stem water content and promotes looser parenchyma cell packing. This study reveals a novel regulatory mechanism of stem strength in pepper, providing a theoretical basis for manipulating plant architecture and breeding mechanization-adapted pepper varieties.