Authors:
Roman Paul Hartwig | University of Hohenheim (340e) | Germany
Michael Santangeli | University of Natural Resources and Life Sciences (BOKU) Vienna
Henrike Würsig | Helmholtz Centre for Environmental Research (UFZ)
María Martín Roldán | Helmholtz Centre for Environmental Research (UFZ)
Bunlong Yim | Julius Kühn-Institut (JKI)
Eva Lippold | Helmholtz Centre for Environmental Research (UFZ)
Ariel Tasca | Technical University of Munich (TUM)
Eva Oburger | University of Natural Resources and Life Sciences (BOKU) Vienna
Mika Tarkka | Helmholtz Centre for Environmental Research (UFZ)
Doris Vetterlein | Helmholtz Centre for Environmental Research (UFZ)
Prof. Patrick Bienert | Technical University of Munich (TUM)
Evgenia Blagodatskaya | Helmholtz Centre for Environmental Research (UFZ)
Kornelia Smalla | Julius Kühn-Institut (JKI)
Monika Wimmer | University of Hohenheim (340e)
Background: Drought stress inconsistently alters root exudation. Little is known about the extent of change, how it affects the soil microbiome, and the spatio-temporal order of responses in the shoot-root-rhizosphere continuum.
Objective: This interdisciplinary study aims to establish whether drought-induced changes in photosynthesis directly affect rhizosphere-based processes, mediated by alterations in root exudates, and modulated by the presence of root hairs.
Materials and Methods: Maize genotypes B73 and rth3 were exposed to a progressive drought, and physicochemical parameters were monitored daily. After 7 d we determined biomass, relative water content (RWC), osmolality, nutrients, metabolomics and proteomics of leaves and roots, RNAseq of roots, root system architecture, fungal and prokaryotic microbiome as well as enzymatic activity of rhizosphere and bulk soil. A second batch of plants was used to collect root exudates.
Results: Both genotypes had a moderate stress level based on RWC, osmolality (leaves) and ABA levels (roots). In roots, drought increased exudation, altered gene expression levels related to drought, immunity and nutrient transporters, and reduced extracellular enzyme activity in the rhizosphere. Drought significantly affected prokaryotic and fungal communities in the bulk soil.
Discussion: A surprisingly fast effect of moderate drought on soil microbial communities correlated with an increase in root exudates. Rhizosphere soil was less affected indicating a “buffering” capacity of roots, either by maintaining a higher water content for microbes at the root surface, or by altering exudation patterns. We expect to identify involved biochemical pathways and consequences for nutrient uptake once metabolomic and RNAseq data are fully evaluated.