Experimental Evidences Of Arabidopsis WRKY45Transcription Factor In Responses To Low-Phosphate Stress

Phosphours is an essential mineral element for plants as it is a component of nuclei acids, ATP and so on. However, plants always have to face the low phosphate of soil, in order to adapt the environment, plants have evolved series strategies to optimize their growth in phosphate-limiting condition. Two of the important responses are linked to root system architecture changing and induction of high-affinity Pi transporters such as PHT1:1and PTH1;4.WRKY transcription factor family belongs to plants uniquely, and some of them are involved in plant responses to biotic and abiotic stresses. This study evaluated the role of WRKY45in regulating phosphate (Pi) uptake in Arabidopsis. WRKY45was localized in the nucleus and mainly expressed in roots. During Pi starvation, WRKY45expression was markedly induced, typically in roots. WRKY45overexpression in Arabidopsis increased Pi content and Pi uptake, while RNAi suppression of WRKY45decreased Pi content and Pi uptake.These results indicate that WRKY45regulates Arabidopsis Pi uptake positively. Real-time PCR results and (3-glucuronidase staining assays showed that PHT1;1expression was enhanced in the35S:WRKY45lines and repressed in the WRKY45RNAi lines. ChIP and EMSA results indicated that WRKY45can bind to two W-boxes within the PHT1;1promoter, confirming the role of WRKY45directly up-regulating PHT1;1expression.phtl;l mutant showed decreased Pi content and Pi uptake, and Super:PHT1;1line resulted in enhanced Pi content and Pi uptake. Furthermore, the Super:PHT1;1line was much more sensitive to arsenate than35S:WRKY45lines and wild-type seedlings, the analogue of phosphate, indicating that PHT1;1overexpression can enhance Arabidopsis Pi uptake.Moreover, the enhanced Pi uptake and the increased arsenate-sensitivity of the35S:WRKY45lines was impaired by pht1;1(35S:WRKY45/pht1;1), demonstrating an epistatic genetic regulation between WRKY45and PHT1;1.Together, our results demonstrate that WRKY45is involved in Arabidopsis response to Pi starvation by direct up-regulation of PHT1;1expression.