Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Tropical Crops, Hainan University, Haikou, Hainan 570228, China.
Key Laboratory of Three Gorges Regional Plant Genetics & Germplasm Enhancement (CTGU)/Biotechnology Research Center, College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, China.
Cell Rep. 2021 Feb 2;34(5):108717. doi: 10.1016/j.celrep.2021.108717.
Heat shock protein 90 (HSP90) is an important molecular chaperone in plants. However, HSP90-mediated plant immune response remains elusive in cassava. In this study, cassava bacterial blight (CBB) induces the expression of MeHsf8, which directly targets MeHSP90.9 to activate its expression and immune response. Further identification of SHI-related sequence 1 (MeSRS1) and MeWRKY20 as MeHSP90.9 co-chaperones revealed the underlying mechanism of MeHSP90.9-mediated immune response. MeHSP90.9 interacts with MeSRS1 and MeWRKY20 to promote their transcriptional activation of salicylic acid (SA) biosynthetic gene avrPphB Susceptible 3 (MePBS3) and tryptophan metabolic gene N-acetylserotonin O-methyltransferase 2 (MeASMT2), respectively, so as to activate SA biosynthesis but inhibit tryptophan-derived auxin biosynthesis. Notably, genetic experiments confirmed that overexpressing MePBS3 and MeASMT2 could rescue the effects of silencing MeHsf8-MeHSP90.9 on disease resistance. This study highlights the dual regulation of SA and auxin biosynthesis by MeHSP90.9, providing the mechanistic understanding of MeHSP90.9 client partners in plant immunity.
热休克蛋白 90（HSP90）是植物中重要的分子伴侣。然而，HSP90 介导的植物免疫反应在木薯中仍难以捉摸。在这项研究中，木薯细菌性条斑病（CBB）诱导 MeHsf8 的表达，MeHsf8 直接靶向 MeHSP90.9，激活其表达和免疫反应。进一步鉴定 SHI 相关序列 1（MeSRS1）和 MeWRKY20 作为 MeHSP90.9 的共伴侣，揭示了 MeHSP90.9 介导免疫反应的潜在机制。MeHSP90.9 与 MeSRS1 和 MeWRKY20 相互作用，分别促进它们对水杨酸（SA）生物合成基因 avrPphB Susceptible 3（MePBS3）和色氨酸代谢基因 N-乙酰血清素 O-甲基转移酶 2（MeASMT2）的转录激活，从而激活 SA 生物合成，但抑制色氨酸衍生的生长素生物合成。值得注意的是，遗传实验证实过表达 MePBS3 和 MeASMT2 可以挽救沉默 MeHsf8-MeHSP90.9 对抗病性的影响。本研究强调了 MeHSP90.9 对 SA 和生长素生物合成的双重调控，为植物免疫中 MeHSP90.9 客户伙伴的机制理解提供了依据。
