Transient overexpression of CpVQ27 reduced the Cucurbita pepo's resistance to powdery mildew

Powdery mildew (PM) is the main disease in pumpkin (Cucurbita pepo) cultivation and one of the main factors affecting Cucurbita pepo yield. The VQ (Valine-Glutamine) proteins play a crucial role in plant responses to abiotic stresses such as drought and salinity, and biotic stress from pathogenic bacteria. Transcriptomic and qPCR analysis showed that after powdery mildew infection for 24 and 48 h, the FPKM and relative expression of CpVQ27 decreased in disease-resistant material F2 and increased in susceptible material M3. Moreover, the FPKM value and relative expression of CpVQ27 in M3 were higher than those in F2. To investigate CpVQ27's responsiveness to powdery mildew infection, we transiently overexpressed CpVQ27 in virus-susceptible variety MRJ. The GFP fluorescence assay, viral disease phenotyping, and qPCR collectively confirmed the successful transient overexpression of CpVQ27 in Cucurbita pepo. Compared to the control group, transient overexpression of CpVQ27 worsened the powdery mildew disease symptoms. Furthermore, the mycelium of powdery mildew grew faster and accumulated more extensively. There was an increase in ROS and MDA content, along with decreased antioxidant enzyme activities and callose levels. Moreover, the expression levels of defense-related genes were reduced. Transient overexpression of CpVQ27 reduced the Cucurbita pepo's resistance to powdery mildew. Our discoveries lay a solid and comprehensive theoretical foundation for future disease resistance breeding.