Transcriptional and Morpho-Physiological Responses of upon Phosphate Starvation.

Phosphate (Pi) is a pivotal nutrient that constraints plant development and productivity in natural ecosystems. Land colonization by plants, more than 470 million years ago, evolved adaptive mechanisms to conquer Pi-scarce environments. However, little is known about the molecular basis underlying such adaptations at early branches of plant phylogeny. To shed light on how early divergent plants respond to Pi limitation, we analyzed the morpho-physiological and transcriptional dynamics of upon Pi starvation. Our phylogenomic analysis highlights some gene networks present since the Chlorophytes and others established in the Streptophytes (e.g., PHR1-SPX1 and STOP1-ALMT1, respectively). At the morpho-physiological level, the response is characterized by the induction of phosphatase activity, media acidification, accumulation of auronidins, reduction of internal Pi concentration, and developmental modifications of rhizoids. The transcriptional response involves the induction of Mp, Pi transporters, lipid turnover enzymes, and Mp, which is an essential transcription factor for auronidins biosynthesis. Mp up-regulation correlates with expression changes in genes related to organic acid biosynthesis and transport, suggesting a preference for citrate exudation. An analysis of MpPHR1 binding sequences (P1BS) shows an enrichment of this regulatory element in differentially expressed genes. Our study unravels the strategies, at diverse levels of organization, exerted by to cope with low Pi availability.