Xero-Branching: discovering how plant roots adapt to reduced water availability

ended

Plant roots forage for key resources like water and nutrients which are often distributed heterogeneously in soil. Plants optimize foraging by employing adaptive responses to modify their root shape. The host laboratory recently discovered (using non-invasive X-ray microCT imaging) that root branching is tightly regulated by the availability of soil moisture. For example, roots growing through an air-filled space transiently repress root branching until re-entering moist soil. This new root adaptive response is termed Xerobranching. Initial studies reveal that Xerobranching is dependent on ABA and auxin responses. However, how these hormone pathways cross-talk to regulate Xerobranching is unclear. Xerobranching is induced by transient accumulation of ABA in root tip tissues following reduced water uptake. Transient water stress also increases levels of protein SUMOylation in plant roots. The host lab recently reported in the journal Science that the transcription factor ARF7 is a target for SUMOylation during transient water stress. I will examine whether Xerobranching requires the ABA-dependent post-translational modification of key lateral root regulator, AUXIN RESPONSE FACTOR 7 (ARF7). I will also investigate whether Xerobranching depends on specific components of the SUMOylation machinery in an ABA-dependent manner. Furthermore, I will explore the wider impact of Xerobranching on soil exploration and crop performance. The highly interdisciplinary project will allow me to master advanced molecular and imaging techniques. This experience will uniquely position me to study adaptive responses at the root-soil interface and exploit allelic variation in key loci to create new varieties of cereal crops with greater foraging abilities.