Devaiah Ballachanda N, Karthikeyan Athikkattuvalasu S, Raghothama Kashchandra G
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907-1165, USA.
Plant Physiol. 2007 Apr;143(4):1789-801. doi: 10.1104/pp.106.093971. Epub 2007 Feb 23.
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 several transcription factors induced during Pi deprivation. In this study, we evaluated the role of the WRKY75 transcription factor in regulating Pi starvation responses in Arabidopsis (Arabidopsis thaliana). WRKY75 was found to be nuclear localized and induced differentially in the plant during Pi deficiency. Suppression of 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, Pi uptake of the mutant plant was also decreased during Pi starvation. In addition, when WRKY75 expression was suppressed, lateral root length and number, as well as root hair number, were significantly increased. However, changes in the root architecture were obvious under both Pi-sufficient and Pi-deficient conditions. This indicates that the regulatory effect of WRKY75 on 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.
磷（Pi）缺乏限制植物生长发育，引发适应性应激反应。在磷胁迫反应的分子决定因素中，转录因子在调节适应性机制方面发挥关键作用。WRKY75是磷缺乏期间诱导产生的几种转录因子之一。在本研究中，我们评估了WRKY75转录因子在调节拟南芥磷饥饿反应中的作用。发现WRKY75定位于细胞核，并且在植物磷缺乏期间差异诱导表达。通过RNA干扰沉默WRKY75的表达导致花青素提前积累，表明RNA干扰植株对磷胁迫更敏感。进一步分析表明，当WRKY75被抑制时，参与磷饥饿反应的几个基因的表达下降，包括磷酸酶、Mt4/TPS1样基因和高亲和力磷转运体。因此，在磷饥饿期间突变植株的磷吸收也减少。此外，当WRKY75表达被抑制时，侧根长度和数量以及根毛数量显著增加。然而，在磷充足和磷缺乏条件下，根系结构的变化都很明显。这表明WRKY75对根系结构的调节作用可能与植物的磷状态无关。总之，这些结果表明WRKY75是磷饥饿反应以及根系发育的调节因子。WRKY75是WRKY转录因子家族中首个被报道参与调节营养饥饿反应和根系发育的成员。
