Ecophysiology of Plants Under Environmental Stress, INRA-SUPAGRO, Institute of Integrative Plant Biology, 2 Place Viala, Montpellier, France.
Plant Sci. 2011 Oct;181(4):387-400. doi: 10.1016/j.plantsci.2011.07.009. Epub 2011 Aug 3.
Myo-inositol is a versatile compound that generates diversified derivatives upon phosphorylation by lipid-dependent and -independent pathways. Phosphatidylinositols form one such group of myo-inositol derivatives that act both as membrane structural lipid molecules and as signals. The significance of these compounds lies in their dual functions as signals as well as key metabolites under stress. Several stress- and non-stress related pathways regulated by phosphatidylinositol isoforms and associated enzymes, kinases and phosphatases, appear to function in parallel to coordinatively adapt growth and stress responses in plants. Recent evidence also postulates their crucial roles in nuclear functions as they interact with the key players of chromatin structure, yet other nuclear functions remain largely unknown. Phosphatidylinositol monophosphate 5-kinase interacts with and represses a cytosolic neutral invertase, a key enzyme of sugar metabolism suggesting a crosstalk between lipid and sugar signaling. Besides phosphatidylinositol, myo-inositol derived galactinol and associated raffinose-family oligosaccharides are emerging as antioxidants and putative signaling compounds too. Importantly, myo-inositol polyphosphate 5-phosphatase (5PTase) acts, depending on sugar status, as a positive or negative regulator of a global energy sensor, SnRK1. This implies that both myo-inositol- and sugar-derived (e.g. trehalose 6-phosphate) molecules form part of a broad regulatory network with SnRK1 as the central regulator. Recently, it was shown that the transcription factor bZIP11 also takes part in this network. Moreover, a functional coordination between neutral invertase and hexokinase is emerging as a sweet network that contributes to oxidative stress homeostasis in plants. In this review, we focus on myo-inositol, its direct and more downstream derivatives (galactinol, raffinose), and the contribution of their associated networks to plant stress tolerance.
肌醇是一种多功能化合物，通过脂质依赖和非依赖途径磷酸化可产生多种衍生物。磷脂酰肌醇就是肌醇衍生物的一个群组，它们既作为膜结构脂质分子，又作为信号分子发挥作用。这些化合物的重要性在于它们作为信号分子和应激下关键代谢物的双重功能。几种由磷脂酰肌醇异构体和相关酶、激酶和磷酸酶调节的应激和非应激相关途径，似乎在植物中与协调适应生长和应激反应的功能平行发挥作用。最近的证据还假设它们在核功能中起关键作用，因为它们与染色质结构的关键参与者相互作用，但其他核功能在很大程度上仍然未知。磷脂酰肌醇单磷酸 5-激酶与细胞质中性转化酶相互作用并抑制其活性，而后者是糖代谢的关键酶，这表明脂质和糖信号之间存在串扰。除了磷脂酰肌醇，肌醇衍生的半乳糖醇和相关的棉子糖家族低聚糖也作为抗氧化剂和潜在的信号化合物出现。重要的是，肌醇多磷酸 5-磷酸酶（5PTase）根据糖的状态，作为全局能量传感器 SnRK1 的正或负调节剂发挥作用。这意味着肌醇和糖衍生的（例如海藻糖 6-磷酸）分子都作为 SnRK1 作为中央调节剂的广泛调控网络的一部分。最近的研究表明，转录因子 bZIP11 也参与了这个网络。此外，中性转化酶和己糖激酶之间的功能协调作为一种甜网络出现，有助于植物的氧化应激稳态。在这篇综述中，我们重点关注肌醇及其直接和更下游的衍生物（半乳糖醇、棉子糖），以及它们相关网络对植物应激耐受性的贡献。
