Lunn John Edward, Delorge Ines, Figueroa Carlos María, Van Dijck Patrick, Stitt Mark
Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany.
Plant J. 2014 Aug;79(4):544-67. doi: 10.1111/tpj.12509. Epub 2014 May 21.
Trehalose is a quantitatively important compatible solute and stress protectant in many organisms, including green algae and primitive plants. These functions have largely been replaced by sucrose in vascular plants, and trehalose metabolism has taken on new roles. Trehalose is a potential signal metabolite in plant interactions with pathogenic or symbiotic micro-organisms and herbivorous insects. It is also implicated in responses to cold and salinity, and in regulation of stomatal conductance and water-use efficiency. In plants, as in other eukaryotes and many prokaryotes, trehalose is synthesized via a phosphorylated intermediate, trehalose 6-phosphate (Tre6P). A meta-analysis revealed that the levels of Tre6P change in parallel with sucrose, which is the major product of photosynthesis and the main transport sugar in plants. We propose the existence of a bi-directional network, in which Tre6P is a signal of sucrose availability and acts to maintain sucrose concentrations within an appropriate range. Tre6P influences the relative amounts of sucrose and starch that accumulate in leaves during the day, and regulates the rate of starch degradation at night to match the demand for sucrose. Mutants in Tre6P metabolism have highly pleiotropic phenotypes, showing defects in embryogenesis, leaf growth, flowering, inflorescence branching and seed set. It has been proposed that Tre6P influences plant growth and development via inhibition of the SNF1-related protein kinase (SnRK1). However, current models conflict with some experimental data, and do not completely explain the pleiotropic phenotypes exhibited by mutants in Tre6P metabolism. Additional explanations for the diverse effects of alterations in Tre6P metabolism are discussed.
海藻糖是许多生物体（包括绿藻和原始植物）中一种在数量上很重要的相容性溶质和应激保护剂。在维管植物中，这些功能在很大程度上已被蔗糖所取代，而海藻糖代谢则承担了新的角色。海藻糖是植物与致病或共生微生物以及食草昆虫相互作用中的一种潜在信号代谢物。它还与对寒冷和盐度的反应以及气孔导度和水分利用效率的调节有关。在植物中，与其他真核生物和许多原核生物一样，海藻糖是通过磷酸化中间体海藻糖6-磷酸（Tre6P）合成的。一项荟萃分析表明，Tre6P的水平与蔗糖平行变化，蔗糖是光合作用的主要产物和植物中的主要运输糖。我们提出存在一个双向网络，其中Tre6P是蔗糖可用性的信号，并起到将蔗糖浓度维持在适当范围内的作用。Tre6P影响白天叶片中积累的蔗糖和淀粉的相对量，并调节夜间淀粉降解的速率以匹配对蔗糖的需求。Tre6P代谢突变体具有高度多效性的表型，在胚胎发生、叶片生长、开花、花序分支和结实方面表现出缺陷。有人提出Tre6P通过抑制SNF1相关蛋白激酶（SnRK1）来影响植物的生长和发育。然而，目前的模型与一些实验数据相冲突，并且不能完全解释Tre6P代谢突变体所表现出的多效性表型。本文还讨论了Tre6P代谢改变产生多种效应的其他解释。
