Plant Physiology Preview Published on February 23, 2007; 10.1104/pp.106.093971
OPEN ACCESS ARTICLE
Received November 30, 2006
Accepted February 20, 2007
WRKY75 Transcription Factor Is a Modulator of Phosphate Acquisition and Root Development in Arabidopsis
Ballachanda N. Devaiah , Athikkattuvalasu S. Karthikeyan , and Kashchandra G. Raghothama *
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907-1165
* Corresponding author; email: kraghoth{at}purdue.edu.
Phosphate (Pi) deficiency limits plant growth and development resulting in adaptive stress responses. Among the molecular determinants of Pi stress responses, transcription factors play a critical role in regulating adaptive mechanisms. WRKY75 is one of the several transcription factors induced during Pi-deprivation. In this study, we evaluated the role of the WRKY75 transcription factor in regulating phosphate starvation responses in Arabidopsis thaliana. WRKY75 was found to be nuclear localized and induced differentially in the plant during Pi-deficiency. Suppression of the WRKY75 expression through RNAi silencing resulted in early accumulation of anthocyanin, indicating that the RNAi plants were more susceptible to Pi stress. Further analysis revealed that the expression of several genes involved in Pi-starvation responses, including phosphatases, Mt4/TPS1-like genes and high affinity Pi transporters was decreased when WRKY75 was suppressed. Consequently, the Pi uptake of the mutant plant was also decreased during Pi-starvation. In addition, when WRKY75 expression was suppressed, the lateral root length and number, as well as the root hair number, were significantly increased. However, changes in the root architecture were obvious both under Pi-sufficient or Pi-deficient conditions. This indicates that the regulatory effect of WRKY75 on the root architecture could be independent of the Pi status of the plant. Together, these results suggest that WRKY75 is a modulator of Pi-starvation responses as well as root development. WRKY75 is the first member of the WRKY transcription factor family reported to be involved in regulating a nutrient starvation response and root development.
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