拟南芥中 Maf1 的表征：应激条件下的功能和 TOR 信号通路的调节,Planta

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拟南芥中 Maf1 的表征：应激条件下的功能和 TOR 信号通路的调节
Planta ( IF 3.6 ) Pub Date : 2018-10-06 , DOI: 10.1007/s00425-018-3024-5
Chang Sook Ahn _{1,

2} , Du-Hwa Lee ₁ , Hyun-Sook Pai ₁

Affiliation

主要结论 Maf1 阻遏物活性对环境胁迫下的植物生存至关重要，并通过 TOR 和 PP4/PP2A 磷酸酶的活性受到其磷酸化/去磷酸化的调节。Maf1 是 RNA 聚合酶 III (Pol III) 的全局阻遏物，在真核生物。Pol III 合成对蛋白质翻译和细胞生长至关重要的小 RNA、5S rRNA 和 tRNA。Maf1 是一种磷蛋白，Maf1 的去磷酸化可促进其在酵母和哺乳动物中的抑制活性。植物 Maf1 在柑橘类植物中被鉴定为一种溃疡病诱发子结合蛋白，柑橘类 Maf1 抑制与溃疡病发展相关的细胞生长。然而，人们对植物 Maf1 在不同胁迫条件下的功能及其对雷帕霉素 (TOR) 信号成分靶标的调节知之甚少。在这项研究中，拟南芥 maf1 突变体比野生型植物更容易受到各种胁迫和 TOR 抑制剂 Torin-1 的处理。maf1 突变体在叶细胞中表达更高水平的 Maf1 靶 RNA，包括 5S rRNA 和前 tRNA，支持拟南芥 Maf1 的 Pol III 阻遏物活性。细胞应激和 Torin-1 处理诱导 Maf1 的去磷酸化，表明 Maf1 在不同的应激条件下激活。TOR 沉默也刺激了 Maf1 去磷酸化，而 PP4 和 PP2A 的催化亚基基因的沉默则抑制了它。因此，TOR 激酶和 PP4/PP2A 磷酸酶似乎相反地调节 Maf1 磷酸化状态。TOR沉默降低了靶RNA的丰度，而PP4和PP2A亚基基因的沉默增加了它，支持 Maf1 去磷酸化与其阻遏物活性之间的正相关。总之，这些结果表明，由 TOR 信号通路调节的 Maf1 的阻遏物活性对于植物细胞在环境胁迫下的存活至关重要。

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Characterization of Maf1 in Arabidopsis: function under stress conditions and regulation by the TOR signaling pathway

Main conclusionMaf1 repressor activity is critical for plant survival during environmental stresses, and is regulated by its phosphorylation/dephosphorylation through the activity of TOR and PP4/PP2A phosphatases.Maf1 is a global repressor of RNA polymerase III (Pol III), and is conserved in eukaryotes. Pol III synthesizes small RNAs, 5S rRNA, and tRNAs that are essential for protein translation and cell growth. Maf1 is a phosphoprotein and dephosphorylation of Maf1 promotes its repressor activity in yeast and mammals. Plant Maf1 was identified in citrus plants as a canker elicitor-binding protein, and citrus Maf1 represses cell growth associated with canker development. However, functions of plant Maf1 under diverse stress conditions and its regulation by the target of rapamycin (TOR) signaling components are poorly understood. In this study, the Arabidopsis maf1 mutants were more susceptible to diverse stresses and treatment with the TOR inhibitor Torin-1 than wild-type plants. The maf1 mutants expressed higher levels of Maf1 target RNAs, including 5S rRNA and pre-tRNAs in leaf cells, supporting Pol III repressor activity of Arabidopsis Maf1. Cellular stresses and Torin-1 treatment induced dephosphorylation of Maf1, suggesting Maf1 activation under diverse stress conditions. TOR silencing also stimulated Maf1 dephosphorylation, while silencing of catalytic subunit genes of PP4 and PP2A repressed it. Thus, TOR kinase and PP4/PP2A phosphatases appeared to oppositely modulate the Maf1 phosphorylation status. TOR silencing decreased the abundance of the target RNAs, while silencing of the PP4 and PP2A subunit genes increased it, supporting the positive correlation between Maf1 dephosphorylation and its repressor activity. Taken together, these results suggest that repressor activity of Maf1, regulated by the TOR signaling pathway, is critical for plant cell survival during environmental stresses.

更新日期：2018-10-06

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