Sun Qingguo, Fan Mingshuo, Qiu Huishan, Zuo Yingtao, Lin Tianyu, Xu Meng, Nie Jiahui, Wu Jiahui, Zhou Jing, Yu Ruimin, Liu Lang, Tian Zhendong
National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University (HZAU), Wuhan, 430070, China.
Hubei Hongshan Laboratory (HZAU), Wuhan, 430070, China.
Plant J. 2025 Mar;121(5):e70074. doi: 10.1111/tpj.70074.
Oomycete pathogens deliver a number of RxLR effector proteins into host plant cells to manipulate immunity by targeting diverse host proteins. Here, we reveal that a Phytophthora infestans RxLR effector Pi18609 targets a potato B-box transcription factor (BBX), StBBX27, which was identified to positively regulate late blight resistance. Silencing the ortholog NbBBX27 in Nicotiana benthamiana or RNA interfering StBBX27 in potato increases host colonization by P. infestans, whereas transient expression of StBBX27 in N. benthamiana or stable overexpression of StBBX27 in potato enhances late blight resistance. Overexpression of StBBX27 in potato activates plant immune responses including upregulation of defense-related genes such as StWRKY8, StOSML13, StCHTB4, and StSERK2, and burst of reactive oxygen species (ROS). In addition, StBBX27 directly binds to the G-box of the WRKY8 and SERK2 promoters and activates their expression, which could be suppressed by Pi18609. Furthermore, we revealed that a ubiquitin E3 ligase COP1 promotes StBBX27 turnover by a proteasome-mediated system. Moreover, Pi18609 promotes the degradation of StBBX27 mediated by COP1. Collectively, this study reveals that StBBX27 positively regulates potato immunity and that is suppressed by effector Pi18609 to promote its turnover. This research extends our knowledge on BBXs function and the mechanisms behind P. infestans effectors suppression of host immunity.
卵菌病原体向宿主植物细胞中输送多种RxLR效应蛋白，通过靶向不同的宿主蛋白来操纵免疫反应。在此，我们揭示了致病疫霉的RxLR效应蛋白Pi18609靶向马铃薯B-box转录因子（BBX）StBBX27，该转录因子被鉴定为正向调控晚疫病抗性。在本氏烟草中沉默直系同源基因NbBBX27或在马铃薯中对StBBX27进行RNA干扰会增加致病疫霉对宿主的定殖，而在本氏烟草中瞬时表达StBBX27或在马铃薯中稳定过表达StBBX27则会增强晚疫病抗性。在马铃薯中过表达StBBX27会激活植物免疫反应，包括上调防御相关基因如StWRKY8、StOSML13、StCHTB4和StSERK2的表达，以及活性氧（ROS）的爆发。此外，StBBX27直接与WRKY8和SERK2启动子的G-box结合并激活它们的表达，而Pi18609可以抑制这种激活。此外，我们还发现泛素E3连接酶COP1通过蛋白酶体介导的系统促进StBBX27的周转。而且，Pi18609促进了由COP1介导的StBBX27的降解。总的来说，这项研究揭示了StBBX27正向调控马铃薯的免疫反应，并且被效应蛋白Pi18609抑制以促进其周转。这项研究扩展了我们对BBXs功能以及致病疫霉效应蛋白抑制宿主免疫背后机制的认识。
