Wang Yunjing, Gong Qian, Wu Yuyao, Huang Fan, Ismayil Asigul, Zhang Danfeng, Li Huangai, Gu Hanqing, Ludman Márta, Fátyol Károly, Qi Yijun, Yoshioka Keiko, Hanley-Bowdoin Linda, Hong Yiguo, Liu Yule
MOE Key Laboratory of Bioinformatics and Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Center for Life Sciences, Beijing 100084, China.
Institute of Genetics and Biotechnology, Hungarian University of Agriculture and Life Sciences, Szent-Györgyi Albert u. 4, Gödöllő 2100, Hungary.
Cell Host Microbe. 2021 Sep 8;29(9):1393-1406.e7. doi: 10.1016/j.chom.2021.07.003. Epub 2021 Aug 4.
RNA interference (RNAi) is an across-kingdom gene regulatory and defense mechanism. However, little is known about how organisms sense initial cues to mobilize RNAi. Here, we show that wounding to Nicotiana benthamiana cells during virus intrusion activates RNAi-related gene expression through calcium signaling. A rapid wound-induced elevation in calcium fluxes triggers calmodulin-dependent activation of calmodulin-binding transcription activator-3 (CAMTA3), which activates RNA-dependent RNA polymerase-6 and Bifunctional nuclease-2 (BN2) transcription. BN2 stabilizes mRNAs encoding key components of RNAi machinery, notably AGONAUTE1/2 and DICER-LIKE1, by degrading their cognate microRNAs. Consequently, multiple RNAi genes are primed for combating virus invasion. Calmodulin-, CAMTA3-, or BN2-knockdown/knockout plants show increased susceptibility to geminivirus, cucumovirus, and potyvirus. Notably, Geminivirus V2 protein can disrupt the calmodulin-CAMTA3 interaction to counteract RNAi defense. These findings link Ca signaling to RNAi and reveal versatility of host antiviral defense and viral counter-defense.
RNA干扰（RNAi）是一种跨生物界的基因调控和防御机制。然而，关于生物体如何感知启动RNAi的初始信号却知之甚少。在此，我们表明，病毒入侵期间对本氏烟草细胞造成的损伤通过钙信号传导激活RNAi相关基因的表达。伤口快速诱导的钙通量升高触发钙调蛋白依赖性激活钙调蛋白结合转录激活因子3（CAMTA3），后者激活RNA依赖性RNA聚合酶6和双功能核酸酶2（BN2）的转录。BN2通过降解其同源微小RNA来稳定编码RNAi机制关键组分的mRNA，特别是AGO1/2和DCL1。因此，多个RNAi基因被启动以对抗病毒入侵。钙调蛋白、CAMTA3或BN2基因敲低/敲除的植物对双生病毒、黄瓜花叶病毒和马铃薯Y病毒的易感性增加。值得注意的是，双生病毒V2蛋白可破坏钙调蛋白-CAMTA3相互作用以对抗RNAi防御。这些发现将钙信号传导与RNAi联系起来，并揭示了宿主抗病毒防御和病毒反防御的多样性。
