Overexpression of pumpkin (Cucurbita pepo L.) CpVQ20 increases resistance to powdery mildew via antioxidant defense and callose accumulation

Abstract

Cucurbita pepo powdery mildew (PM) is mainly caused by Podosphaera xanthii. It can readily induce wilting of pumpkin (Cucurbita pepo L.) branches and leaves, and may even lead to stunted growth and fruit deformities, significantly impacting both the quality and yield of Cucurbita pepo. VQ (Valine-glutamine) proteins play a crucial role in enhancing plant resistance to various abiotic and biotic stresses. In this study, qPCR analysis showed that after powdery mildew infection, the relative expression of CpVQ20 increased in disease-resistant material F2 and decreased in susceptible material M3. Cucurbita pepo CpVQ20 was localized in the nucleus. We observed a reduced incidence of powdery mildew in CpVQ20-overexpression (OE) plants compared to the wild-type (WT). Furthermore, powdery mildew mycelium grew slower and accumulated less. The activities of antioxidases were enhanced, while the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) were diminished. Overexpression of CpVQ20 increased callose content in Cucurbita pepo. The expression levels of callose synthase gene and defense-associated genes were elevated. This study concludes that CpVQ20 positively regulates resistance to powdery mildew. This pioneering research establishes a robust foundation for future breakthroughs in gene improvement and genetic breeding.