Abstract
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. The WRKY42-overexpressing lines, similar to the phosphate1 (pho1) mutant, were more sensitive to low-inorganic phosphate (Pi) stress and had lower shoot Pi content compared with wild-type plants. The PHO1 expression was repressed in WRKY42-overexpressing lines and enhanced in the wrky42 wrky6 double mutant. The WRKY42 protein bound to the PHO1 promoter under Pi-sufficient condition, and this binding was abrogated during Pi starvation. These data indicate that WRKY42 modulated Pi translocation by regulating PHO1 expression. Furthermore, overexpression of WRKY42 increased root Pi content and Pi uptake, whereas the wrky42 mutant had lower root Pi content and Pi uptake rate compared with wild-type plants. Under Pi-sufficient condition, WRKY42 positively regulated PHOSPHATE TRANSPORTER1;1 (PHT1;1) expression by binding to the PHT1;1 promoter, 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 of PHO1 and PHT1;1 to adapt to environmental changes in Pi availability.
Highlights
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
The PHOSPHATE TRANSPORTER TRAFFIC FACILITATOR1 (PHF1) protein is necessary for PHOSPHATE TRANSPORTER1;1 (PHT1);1 plasma membrane localization, and mutation of PHF1 impairs the localization of PHT1;1 at the plasma membrane (González et al, 2005)
We report that Arabidopsis WRKY42 plays important roles in modulating Pi homeostasis in Arabidopsis
Summary
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. The WRKY42 protein bound to the PHO1 promoter under Pi-sufficient condition, and this binding was abrogated during Pi starvation These data indicate that WRKY42 modulated Pi translocation by regulating PHO1 expression. E2 conjugase PHOSPHATE2 (PHO2) modulates PHT1;1 protein degradation (Huang et al, 2013), and NITROGEN LIMITATION ADAPTATION mediates PHT1;1 and PHT1;4 degradation to Another important pathway controlling Pi homeostasis involves PHO1, which plays an important role in Pi translocation from roots to shoots (Poirier et al, 1991; Hamburger et al, 2002; Wang et al, 2004). PHO2 can modulate PHO1 degradation (Liu et al, 2012)
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