Xiao Siyu, Wang Jinhui, Bai Zihan, Jiang Haibin, Zhu Jiehua, Yang Zhihui
Hebei Agricultural University, College of Plant Protection, Baoding, Hebei, China.
Technological Innovation Center for Biological Control of Crop Diseases and Insect Pests of Hebei Province, Baoding, China.
Mol Plant Pathol. 2025 Jun;26(6):e70109. doi: 10.1111/mpp.70109.
Alternaria solani is an important necrotrophic pathogen causing potato early blight. However, the pathogenic molecular mechanisms of A. solani remain unclear. Previous work identified a specific effector AsCEP20 in A. solani through multi-omics analysis. AsCEP20 is required for the full virulence of A. solani and targets the host chloroplasts. In this study, we screened out 46 candidate proteins that potentially interact with AsCEP20 in Nicotiana benthamiana using co-immunoprecipitation followed by liquid chromatography-tandem mass spectrometry analysis. We identified a candidate target protein in potato, filamentation temperature-sensitive H4 (StFtsH4), which is located in chloroplasts, based on homologous alignment and subcellular localisation analysis. The interaction between AsCEP20 and StFtsH4 was further confirmed by co-immunoprecipitation, yeast two-hybrid assay and bimolecular fluorescence complementation assays. The interaction site between AsCEP20 and StFtsH4 is also the chloroplast. Silencing the potato StFtsH4 gene resulted in suppressed pathogen-associated molecular pattern-triggered reactive oxygen species (ROS) bursts, and defence-related genes were significantly downregulated. These results suggest that StFtsH4 positively regulates plant immunity. Therefore, AsCEP20 targets the chloroplast protein StFtsH4 to promote pathogen infection. AsCEP20 attenuates the efficiency of light energy utilisation in photosynthesis by targeting StFtsH4. These results suggest that AsCEP20 suppresses StFtsH4-mediated potato disease resistance to A. solani. With the increase of light intensity, ROS continued to accumulate in the chloroplast of StFtsH4-silenced plant leaves, while defence-related genes significantly decreased. Our findings reveal that the impaired StFtsH4 function limits plant photosynthesis, thereby affecting immune signalling.
链格孢菌是引起马铃薯早疫病的一种重要的坏死营养型病原菌。然而，链格孢菌的致病分子机制仍不清楚。先前的研究通过多组学分析在链格孢菌中鉴定出一种特异性效应蛋白AsCEP20。AsCEP20是链格孢菌完全致病力所必需的，并且靶向宿主叶绿体。在本研究中，我们通过免疫共沉淀结合液相色谱-串联质谱分析，在本氏烟草中筛选出46种可能与AsCEP20相互作用的候选蛋白。基于同源比对和亚细胞定位分析，我们在马铃薯中鉴定出一种位于叶绿体中的候选靶蛋白，即丝状温度敏感蛋白H4（StFtsH4）。通过免疫共沉淀、酵母双杂交试验和双分子荧光互补试验进一步证实了AsCEP20与StFtsH4之间的相互作用。AsCEP20与StFtsH4之间的相互作用位点也是叶绿体。沉默马铃薯StFtsH4基因导致病原菌相关分子模式触发的活性氧（ROS）爆发受到抑制，并且与防御相关的基因显著下调。这些结果表明StFtsH4正向调节植物免疫。因此，AsCEP20靶向叶绿体蛋白StFtsH4以促进病原菌感染。AsCEP20通过靶向StFtsH4降低光合作用中光能利用的效率。这些结果表明AsCEP20抑制StFtsH4介导的马铃薯对链格孢菌的抗病性。随着光照强度的增加，ROS在StFtsH4沉默植株叶片的叶绿体中持续积累，而与防御相关的基因显著减少。我们的研究结果表明，StFtsH4功能受损会限制植物光合作用，从而影响免疫信号传导。
