Physiological drought stress imprints related to root exudation in the rhizosphere

• Applicant: Dr. Monika Wimmer
• Subject Area: Plant Cultivation, Plant Nutrition, Agricultural Technology
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 403626025

In Central Europe, transient drought spells are predicted to increase due to climate change. So-called “stress imprints” describe modifications in plants that occur after a stress event and improved responses to subsequent stresses. Such modifications are in the focus of this project. Root exudates are altered under drought stress to facilitate root growth into the drying soil, but it remains an open question (i) whether physiological drought stress imprints related to root exudation occur in the rhizophere, (ii) in which spatio-temporal pattern root exudation responds to stress severity, duration and stress onset type, and (iii) how metabolic re-organization of the root system in response to drought affects post-stress plant performance with respect to stress resilience and nutrient uptake.This project addresses four hypotheses: (1) physiological drought stress imprints occur in the rhizosphere and are mediated by altered root exudation; (2) the extent of these imprints depends on the speed of onset, severity and duration of the drought event and concomittant damage to the photosystem; (3) these imprints lead to spatio-temporal re-distribution of resources towards the root and (4) they affect post-stress plant performance with respect to water and nutrient uptake. In this project, plants are exposed to different drought stress types including different intensities, durations and speeds of progression. Exudate production is determined by collecting exudates and composition is assessed by LC-MS analyses. Photosynthesis-related processes are monitored during the progression of drought, and damage to the photosystem is assessed by chlorophyll fluorescence and biochemical stress markers. The persistence of the stress imprints is determined by time course analysis during re-watering. In a rhizobox setup, one half of the roots is exposed to a single, and one half to recurrent drought drought spells. Root exudates are collected from both root halves and metabolic reorganisation of the whole plant as well as metabolic crosstalk between the root halves is monitored using a proteomic approach. Post stress plant performance is analysed by assessing the recovery time for water relations in the plant and uptake of nutrients, complemented by expression studies of aquaporins and selected nutrient transporters. The pot experiments are complemented by similar analyses of exudates collected from root windows in the field.The outcomes of these studies will provide information on the spatio-temporal interplay between drought-induced changes in photosynthetic processes aboveground, and their lasting imprints on rhizosphere-based processes belowground, mediated by alterations in root exudates. They help to gain a mechanistic understanding of underlying metabolic responses of the system root/shoot which may lead to an improved post-stress performance under conditions of sub-optimum growth conditions after drought.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2089: Rhizosphere Spatiotemporal Organisation - a Key to Rhizosphere Functions
• International Connection: Austria
• Cooperation Partner: Professorin Dr. Stefanie Wienkoop