Differential TOR activation and cell proliferation in Arabidopsis root and shoot apexes
Differential TOR activation and cell proliferation in Arabidopsis root and shoot apexes
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DOI：
10.1073/pnas.1618782114
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发表时间：
2017-03-07
影响因子：
11.1
通讯作者：
Xiong, Yan
中科院分区：
文献类型：
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作者：
Li, Xiaojuan;Cai, Wenguo;Xiong, Yan
植物的发育可塑性依赖于分生组织将营养和能量的可利用性与环境信号相结合的非凡能力。根尖和顶端的分生组织具有高度相似的分子成员，但在空间上被土壤分开。这两个分生组织是否以及如何对局部营养、激素和环境信号(如光)具有不同的激活要求，在光合作用植物中仍然是一个谜。在这里，我们报告了根尖和茎尖的激活依赖于不同的葡萄糖和光信号。葡萄糖能量信号足以激活根尖的雷帕霉素(TOR)激酶靶标。相反，葡萄糖和光信号都是TOR在茎尖激活所必需的。值得注意的是，外源生长素能够取代光激活顶端的TOR，促进真叶的发育。地上部生长素浓度相对较低，而根部生长素浓度较高，这可能是根尖和顶端这种独特的光需求的原因，因为光是促进地上部生长素生物合成所必需的。此外，我们还揭示了小GTP酶Rho相关蛋白2(ROP2)通过直接相互作用转导光生长素信号来激活TOR，进而促进转录因子E2Fa，b来激活茎尖中的细胞周期基因。即使在没有光的情况下，结构性激活的ROP2植株也会刺激顶端的TOR，并导致真正的叶片发育。综上所述，我们的发现确立了TOR信号在整合不同环境信号以调节不同的发育过渡和地上部和根部生长方面的关键枢纽作用。
The developmental plasticity of plants relies on the remarkable ability of the meristems to integrate nutrient and energy availability with environmental signals. Meristems in root and shoot apexes share highly similar molecular players but are spatially separated by soil. Whether and how these two meristematic tissues have differential activation requirements for local nutrient, hormone, and environmental cues (e.g., light) remain enigmatic in photosynthetic plants. Here, we report that the activation of root and shoot apexes relies on distinct glucose and light signals. Glucose energy signaling is sufficient to activate target of rapamycin (TOR) kinase in root apexes. In contrast, both the glucose and light signals are required for TOR activation in shoot apexes. Strikingly, exogenously applied auxin is able to replace light to activate TOR in shoot apexes and promote true leaf development. A relatively low concentration of auxin in the shoot and high concentration of auxin in the root might be responsible for this distinctive light requirement in root and shoot apexes, because light is required to promote auxin biosynthesis in the shoot. Furthermore, we reveal that the small GTPase Rho-related protein 2 (ROP2) transduces light-auxin signal to activate TOR by direct interaction, which, in turn, promotes transcription factors E2Fa,b for activating cell cycle genes in shoot apexes. Consistently, constitutively activated ROP2 plants stimulate TOR in the shoot apex and cause true leaf development even without light. Together, our findings establish a pivotal hub role of TOR signaling in integrating different environmental signals to regulate distinct developmental transition and growth in the shoot and root.