Inositol as a regulator of seedling development

点击翻译按钮获取中文摘要

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.