Uncovering the mechanisms of the root gravitropic set-point angle and its application in agriculture

Root system architecture determines the ability of plants to take up water and nutrients from the soil. The gravitropic set-point angle (GSA) describes the orientation of single roots to the gravitropic vector and is therefore essential for shaping the root system architecture. The GSA differs between root types and even between roots of the same type and can be adapted according to environmental conditions. However, to date it is still largely unknown which signalling pathways maintain the GSA and how the environmental cues are transduced to changes in the angle. Here we propose to use RNA sequencing of barley seminal roots with different GSAs to understand the transcriptomic basis of GSA maintenance. We will then compare the data set to existing transcriptome datasets of the hypergravitropic barley mutant enhanced gravitropism2 (egt2) and of barley roots after rotation to identify candidate genes. These candidate genes we will analyse regarding their expression and mutant phenotype. In parallel, we will dissect the signalling pathway of EGT2 in more detail, by analysing the expression pattern and screening for interaction partners. To understand the influence of the root growth angle in water and nutrient uptake, we will use the egt2 mutant as well as mutants derived from the transcriptome data set, to test plant performance under different challenging soil conditions, such as drought or phosphate starvation. With this proposed project, we hope to gain new insights into GSA signalling and a better understanding for the connection of the root growth angle to different soil conditions.