WRKY42 Modulates Phosphate Homeostasis through Regulating Phosphate Translocation and Acquisition in Arabidopsis

The Arabidopsis (Arabidopsis thaliana) WRKY transcription factor family has more than 70 members, and some of them have been reported to play important roles in plant response to biotic and abiotic stresses. This study shows that WRKY42 regulated phosphate homeostasis in Arabidopsis. TheWRKY42-overexpressing lines, similar to thephosphate1(pho1) mutant, were more sensitive to low-inorganic phosphate (Pi) stress and had lower shoot Pi content compared with wild-type plants. ThePHO1expression was repressed inWRKY42-overexpressing lines and enhanced in thewrky42 wrky6double mutant. The WRKY42 protein bound to thePHO1promoter under Pi-sufficient condition, and this binding was abrogated during Pi starvation. These data indicate that WRKY42 modulated Pi translocation by regulatingPHO1expression. Furthermore, overexpression ofWRKY42increased root Pi content and Pi uptake, whereas thewrky42mutant had lower root Pi content and Pi uptake rate compared with wild-type plants. Under Pi-sufficient condition, WRKY42 positively regulatedPHOSPHATE TRANSPORTER1;1(PHT1;1) expression by binding to thePHT1;1promoter, and this binding was abolished by low-Pi stress. During Pi starvation, the WRKY42 protein was degraded through the 26S proteasome pathway. Our results showed that AtWRKY42 modulated Pi homeostasis by regulating the expression ofPHO1andPHT1;1to adapt to environmental changes in Pi availability.