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Life Sciences Seminar. Dr Christa Testerink, University of Amsterdam.
Title. Take it or leave it: How plant roots avoid salt
Summary. To deal with drought, high salinity, or nutrient deprivation, plants adjust and optimize their root system architecture. We study the intracellular signalling pathways linking salinity stress to root development and direction of root growth.
By quantifying root system architecture (RSA) dynamics of 31 different Arabidopsis accessions in mild salt stress conditions, differential regulation of main and lateral root growth rate and root branching were revealed. Applying ROOT-FIT to describe the dynamics of RSA allowed us to uncover the natural diversity in root morphology and cluster it into four response types that otherwise would have been overlooked. RSA strategies partially correlated with natural variation in abscisic acid sensitivity and different Na+/K+ ratios in shoots of seedlings grown under mild salt stress.
In addition to changing their overall RSA, a variety of plant species can also selectively change direction of root growth, to avoid high salt concentrations. Directionality of this response is established by an active redistribution of the plant hormone auxin in the root tip, which is mediated by lipid-dependent clathrin-mediated endocytosis of the PIN-FORMED 2 (PIN2) auxin efflux carrier. Our results thus identify a cellular pathway essential for plant responses to salt stress, which may serve to integrate multiple environmental signals to optimize root growth in response to changing conditions.