Mechanisms of root system adaptation to hypoxic stress in Arabidopsis

• Applicant: Professorin Dr. Jennifer Selinski, since 7/2023
• Subject Area: Plant Physiology
• Term: from 2018 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 415031136

Plants are aerobic organisms. Oxygen shortage is a constraint because it prevents mitochondrial respiration, a major source of the universal energy unit ATP. Soil waterlogging and flooding are common causes of oxygen shortage and hence of energy restriction in roots. Growth requires energy and can be limited by energy supply. However, using the model plant Arabidopsis thaliana, we recently revealed that oxygen shortage does not simply result in root growth inhibition but in controlled reshaping of the root system. The primary root changes its growth direction when exposed to hypoxia, most likely to escape to better aerated soil layers. Molecular analysis revealed that root bending is controlled by the transcription factor RAP2.12, a member of group VII Ethylene Response Factors (ERFVII) that act as oxygen sensors in plants. At the primary root tip, RAP2.12 reduces the protein level of PIN2, a polar auxin transporter, and increases local auxin activity thereby modulating the degree of root bending. We further showed that lateral roots undergo a transient growth arrest after emergence from the maternal root during the first days of hypoxia after which they resume growth. Rescue of lateral root elongation is dependent on ERFVIIs and appears to be controlled through changes in abscisic acid levels that transiently decline due to elevated expression of abscisic acid-8’-hydroxylase genes. Altered primary root growth direction and delayed lateral root growth contribute to an overall altered root system architecture as a result of low oxygen stress. From these findings, it has become clear that root system development is actively controlled during, and despite of, oxygen shortage with ERFVIIs as key regulators. Auxin and abscisic acid are targets of ERFVIIs indicating that low oxygen signaling taps into hormonal pathways for developmental reprogramming of the root system. While we have identified some of the key players, we still need to elucidate in more detail the molecular mechanisms underlying root bending and lateral root elongation. For instance, we need to understand how PIN2 abundance and auxin distribution are altered by RAP2.12. What are the primary target genes of ERFVIIs that alter root development? And there is a need to evaluate the impact of root system architecture on flooding tolerance in the long term. This project aims to address these issues and will contribute to uncover the molecular mechanisms of root system development in response to oxygen shortage.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Professorin Dr. Margret Sauter, until 7/2023 (†)