Plants feature remarkable developmental plasticity, enabling them to respond to and cope with environmental cues, such as limited availability of phosphate, an essential macronutrient for all organisms. Under these adverse conditions, Arabidopsis roots undergo striking morphological changes, including exhaustion of the primary meristem, impaired unidirectional cell expansion and elevated density of lateral roots. Recently, the activity of two homologous brassinosteroid transcriptional effectors, BZR1 and BES1/BZR2, were shown to block these responses, consequently maintaining normal root development under low phosphate conditions, without impacting phosphate homeostasis. Our preliminary data suggests that BZR1 and BES1/BZR2 blocks this modulation of root system architecture (RSA) from a specific tissue of the root, the endodermis. Hence, we propose to identify BZR1 and BES1/BZR2 direct (and potentially universal) targets in at least two plant species: Arabidopsis and tomato, in a tissue specific manner. By applying rapid, genome-scale tools already available in Arabidopsis, with a newly developed tool kit that enables rapid molecular manipulations in tomato, we will perform RNA-seq analyses in specific tissues of the root, designed to identify these targets. Functional analysis of these conserved genes in both plant species, will be used to validate their role in RSA control, in response to phosphate-limited conditions. The proposed research is expected to contribute a step forward towards understanding the fundamentals of environmentally controlled developmental switch from deep to shallower root architecture. Furthermore, identification of conserved components and their tissue of action during root adaptation to low Pi availability can be leveraged toward potential biotechnology improvement of plant performance, specifically in tomato and other vegetable crops.
PIs: Sigal Savaldi-Goldstein (Technion, Israel) and Siobhan Brady (UC Davis)
Binational Agricultural Research and Development Fund