The Deubiquitinase OTU5 Regulates Root Responses to Phosphate Starvation.

Phosphorus, taken up by plants as inorganic phosphate (Pi), is an essential but often growth-limiting mineral nutrient for plants. As part of an orchestrated response to improve its acquisition, insufficient Pi supply triggers alterations in root architecture and epidermal cell morphogenesis. Arabidopsis () mutants defective in the expression of the () exhibited a constitutive Pi deficiency root phenotype, comprising the formation of long and dense root hairs and attenuated primary root growth. Quantitative protein profiling of and wild-type roots using the isobaric tag for relative and absolute quantification methodology revealed genotype- and Pi-dependent alterations in protein profiles. In plants, Pi starvation caused a short-root-hair phenotype and decreased abundance of a suite of Pi-responsive root hair-related proteins. Mutant plants also showed the accumulation of proteins involved in chromatin remodeling and altered distribution of reactive oxygen species along the root, which may be causative for the alterations in root hair morphogenesis. The root hair phenotype of was synergistic to that of (), harboring a mutation in the SWR1 chromatin-remodeling complex. Genetic analysis of double mutants suggests independent but functionally related roles of the two proteins in chromatin organization. The root hair phenotype of is not caused by a general up-regulation of the Pi starvation response, indicating that OTU5 acts downstream of or interacts with Pi signaling. It is concluded that OTU5 is involved in the interpretation of environmental information, probably by altering chromatin organization and maintaining redox homeostasis.