Tang Lin, Zhu Liangliang, Wu Xinyun, Tian Runze, Bai Yayuan, Tian Xiangrong, Zhang Daoyuan, Huang Lili
State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, China.
State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Forestry, Northwest A&F University, Yangling, Shaanxi, China.
Mol Plant Pathol. 2025 Jun;26(6):e70106. doi: 10.1111/mpp.70106.
Through co-evolutionary adaptation, phytopathogenic fungi have evolved specialised host preference mechanisms to optimise infection efficacy. Fungi of the Valsa genus infect various Rosaceae fruit trees, with Valsa mali exhibiting a marked host preference for apple trees, while Valsa pyri preferentially colonises pear trees. The divergent secondary metabolite biosynthetic gene clusters (SMBGCs) between these two species may serve as key determinants of their distinct host preferences. In this study, VmPKS5, a polyketide synthase, was identified as a key factor influencing the host preference of V. mali, which is the main pathogen of apple Valsa canker (AVC). Deletion of VmPKS5 greatly reduced the virulence of V. mali in apple trees, but not in pear trees. Deletion of VmPKS5 completely abolished the production of the toxin p-coumaric acid ethyl ester (p-CAEE). Exogenous p-CAEE application partly restored the virulence of ΔVmPKS5 and enhanced the virulence of the wild-type strain of V. mali. Crucially, heterologous expression of VmPKS5 in V. pyri increased its virulence towards apple trees by production of p-CAEE during infection. Notably, V. mali can uptake double-stranded RNA (dsRNA), and exogenous spray of VmPKS5-dsRNA significantly inhibited the infection by V. mali. This study provides new perspectives on host preference mechanisms of fungal pathogens and green disease control of tree disease by dsRNA fungicides.
通过共同进化适应，植物病原真菌已经进化出专门的寄主偏好机制以优化感染效果。黑腐皮壳属真菌可感染多种蔷薇科果树，其中苹果黑腐皮壳对苹果树表现出明显的寄主偏好，而梨黑腐皮壳则优先定殖于梨树上。这两个物种之间不同的次生代谢物生物合成基因簇（SMBGCs）可能是其不同寄主偏好的关键决定因素。在本研究中，聚酮合酶VmPKS5被鉴定为影响苹果黑腐皮壳寄主偏好的关键因子，苹果黑腐皮壳是苹果腐烂病的主要病原菌。敲除VmPKS5极大地降低了苹果黑腐皮壳在苹果树上的毒力，但在梨树上没有。敲除VmPKS5完全消除了毒素对香豆酸乙酯（p-CAEE）的产生。外源施用p-CAEE部分恢复了ΔVmPKS5的毒力并增强了苹果黑腐皮壳野生型菌株的毒力。至关重要的是，VmPKS5在梨黑腐皮壳中的异源表达通过在感染期间产生p-CAEE增加了其对苹果树的毒力。值得注意的是，苹果黑腐皮壳可以摄取双链RNA（dsRNA），外源喷施VmPKS5-dsRNA显著抑制了苹果黑腐皮壳的感染。本研究为真菌病原体的寄主偏好机制以及dsRNA杀菌剂对树木病害的绿色防治提供了新的视角。
