Jiahao Liang# , Jie Wang, Kai Wang, Hao Feng* and Lili Huang*,VmRDR2 of Valsa mali mediates the generation of VmR2-siR1 that suppresses apple resistance by RNA interference. New Phytologist , 2024, doi: 10.1111/nph.19867.

Summary

Cross-kingdom RNA interference (RNAi) is a crucial mechanism in host–pathogen interactions, with RNA-dependent RNA polymerase (RdRP) playing a vital role in signal amplification during RNAi. However, the role of pathogenic fungal RdRP in siRNAs generation and the regulation of plant–pathogen interactions remains elusive.

 Using deep sequencing, molecular, genetic, and biochemical approaches, this study revealed that VmRDR2 of Valsa mali regulates VmR2-siR1 to suppress the disease resistance-related gene MdLRP14 in apple.

 Both VmRDR1 and VmRDR2 are essential for the pathogenicity of V. mali in apple, with VmRDR2 mediating the generation of endogenous siRNAs, including an infection-related siRNA, VmR2-siR1. This siRNA specifically degrades the apple intracellular LRR-RI protein gene MdLRP14 in a sequence-specific manner, and overexpression of MdLRP14 enhances apple resistance against V. mali, which can be suppressed by VmR2-siR1. Conversely, MdLRP14 knockdown reduces resistance.

 In summary, this study demonstrates that VmRDR2 contributes to the generation of VmR2-siR1, which silences the host’s intracellular LRR protein gene, thereby inhibiting host resistance. These findings offer novel insights into the fungi-mediated pathogenicity mechanism through RNAi.

https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.19867