Phosphate starvation responses. Insights from the identification of PHR1 targets and from studies on natural variation

Plants have evolved an array of adaptive responses to cope with groth under lo phosphate (Pi) regimens, and involve developmental, physiological changes aiming to increase Pi acquisition and use efficiency and to protect the plant from the stress caused by Pi starvation. This adaptive system has recently received great attention, not only for its suitability as a model to study regulation of gene activity, but also for its importance in the context of generating plants requiring less Pi fertilizer. In this communication, we will refer to our studies on the PHR1 transcription factor and on natural variation of the Pi starvation transcriptome. PHR1 is a master regulator of the Pi starvation rescue system, controlling most of the responses associated to this system and integrating Pi signals and other modulators of PSR (eg, cytokinins and sucrose). We found PHR1 recognizes more than 2500 targets which are enriched in Pi starvation induced genes. Pi starvation induced PHR1 targets are enriched in drought response genes. In line with this we found that Pi starvation provokes a reduction in water content, which likely represents an adaptive response as it is mediated by PHR1. As for natural variation studies, I will refer to the analysis of the Pi starvation transcriptome in 5 Arabidopsis ecotypes and to an eQTL analysis of a RIL population ColxCt-1