Inositol as a regulator of seedling development

环糖醇肌醇在植物的各种代谢途径中起着重要作用。肌醇可以通过从头生物合成从葡萄糖衍生，但也可以通过肌醇转运蛋白输入细胞或从液泡释放。细胞内肌醇含量的变化，例如在生物合成突变体中，导致多效性效应，例如含肌醇的膜组分的水平改变，膜动力学受影响和幼苗发育缺陷。此外，生长素信号通过改变生长素流出载体的膜定位而受损。拟南芥有三种转运蛋白用于将肌醇输入胞质溶胶：质膜中的AtINT 2和AtINT 4以及液泡膜中的AtINT 1。如果AtINT 1蛋白，运输肌醇的液泡进入细胞质，是失踪，这些Atint 1幼苗表现出抑制细胞伸长的根和黄化的下胚轴。这仅在向生长培养基中添加蔗糖时发生。Atint1植物生长在培养基上没有蔗糖没有表现出明显的生长差异相比，野生型，但增加了水平的肌醇含有膜组件。Atint 1幼苗与肌醇生物合成缺陷突变体的比较表明，所观察到的表型差异并不依赖于肌醇缺乏，而是依赖于细胞内肌醇分布的不平衡。由于肌醇参与许多不同的过程，我们将采用各种方法来科普肌醇转运改变的多效性效应。分析的代谢物的收集将扩大，例如，将包括在植物中具有假定信号功能的磷酸化肌醇。将分析蔗糖是否作为营养分子或信号分子发挥作用。由于肌醇参与各种代谢途径，对编码肌醇代谢关键酶的基因的表达分析将揭示Atint 1突变体中哪些代谢途径发生了改变，Atint 1幼苗中生长素流出载体的定位和使植物中生长素分布可视化的生长素响应标记的使用将阐明缺失的肌醇转运和生长素信号传导之间的潜在联系。此外，研究将集中在Atint 1植物与野生型相比的进一步表型差异上，例如向重力性，肌醇的贡献已经被描述。

The cyclic sugar alcohol inositol plays a central role in various metabolic pathways in plants. Inositol can be derived from glucose via de novo-biosynthesis, but also be imported into the cell or released from the vacuole via inositol transport proteins. Changes in intracellular inositol content, e.g. in biosynthesis mutants, lead to pleiotropic effects such as altered levels of inositol-containing membrane components, affected membrane dynamics and defects in seedling development. Moreover, auxin signalling is impaired by changing the membrane localisation of auxin efflux carriers.Arabidopsis thaliana has three transport proteins for the import of inositol into the cytosol: AtINT2 and AtINT4 in the plasma membrane and AtINT1 in the tonoplast. If the AtINT1 protein, which transports inositol out of the vacuole into the cytoplasm, is missing, these Atint1 seedlings show an inhibition of cell elongation in roots and in etiolated hypocotyls. This only occurs when sucrose is added to the growth medium. Atint1 plants grown on medium without sucrose do not show apparent growth differences compared to wild type, but have increased levels of inositol-containing membrane components. Comparison of Atint1 seedlings with mutant plants defective in inositol biosynthesis revealed that the observed phenotypic differences do not rely on inositol deficiency, but rather on imbalance in intracellular inositol distribution.The aim of this project is to unravel the impact of inositol balance maintained by intracellular inositol transport on plant development. Because inositol is involved in many different processes we will perform various approaches to cope with the pleiotropic effects of altered inositol transport. The collection of metabolites analysed will be extended, e.g. phosphorylated inositols with supposed signalling function in plants will be included.It will be analysed, if sucrose plays a role as nutrimental or signalling molecule.Due to the fact that inositol is involved in various metabolic pathways, expression analysis of genes encoding key enzymes in inositol metabolism will reveal which metabolic pathways are changed in the Atint1 mutant compared to wild type.Localisation of auxin effluc carriers in Atint1 seedlings and use of an auxin response marker that visualises auxin distribution in plants will elucidate a potential connection between missing inositol transport and auxin signalling. Additionally, research will focus on further phenotypic differences of Atint1 plants compared to wild type, e.g. gravitropism, for which a contribution of inositol was already described.