Department of Plant and Microbial Biology, North Carolina State University Raleigh, NC, USA.
Front Plant Sci. 2014 Jun 11;5:267. doi: 10.3389/fpls.2014.00267. eCollection 2014.
The phosphoinositide pathway and inositol-1,4,5-triphosphate (InsP3) have been implicated in plant responses to many abiotic stresses; however, their role in response to biotic stress is not well characterized. In the current study, we show that both basal defense and systemic acquired resistance responses are affected in transgenic plants constitutively expressing the human type I inositol polyphosphate 5-phosphatase (InsP 5-ptase) which have greatly reduced InsP3 levels. Flagellin induced Ca(2+)-release as well as the expressions of some flg22 responsive genes were attenuated in the InsP 5-ptase plants. Furthermore, the InsP 5-ptase plants were more susceptible to virulent and avirulent strains of Pseudomonas syringae pv. tomato (Pst) DC3000. The InsP 5-ptase plants had lower basal salicylic acid (SA) levels and the induction of SAR in systemic leaves was reduced and delayed. Reciprocal exudate experiments showed that although the InsP 5-ptase plants produced equally effective molecules that could trigger PR-1 gene expression in wild type plants, exudates collected from either wild type or InsP 5-ptase plants triggered less PR-1 gene expression in InsP 5-ptase plants. Additionally, expression profiles indicated that several defense genes including PR-1, PR-2, PR-5, and AIG1 were basally down regulated in the InsP 5-ptase plants compared with wild type. Upon pathogen attack, expression of these genes was either not induced or showed delayed induction in systemic leaves. Our study shows that phosphoinositide signaling is one component of the plant defense network and is involved in both basal and systemic responses. The dampening of InsP3-mediated signaling affects Ca(2+) release, modulates defense gene expression and compromises plant defense responses.
磷脂酰肌醇途径和肌醇 1,4,5-三磷酸 (InsP3) 已被牵涉到植物对许多非生物胁迫的反应中；然而，它们在生物胁迫反应中的作用尚未得到很好的描述。在本研究中，我们表明，在持续表达人类 I 型肌醇多磷酸 5-磷酸酶（InsP 5-ptase）的转基因植物中，基础防御和系统获得性抗性反应均受到影响，这些植物的 InsP3 水平大大降低。鞭毛蛋白诱导的 Ca2+释放以及一些 flg22 响应基因的表达在 InsP 5-ptase 植物中受到抑制。此外，InsP 5-ptase 植物对丁香假单胞菌 pv.番茄（Pst）DC3000 的毒性和非毒性菌株更为敏感。InsP 5-ptase 植物的基础水杨酸（SA）水平较低，系统叶片中的 SAR 诱导减少且延迟。相互渗出实验表明，尽管 InsP 5-ptase 植物产生了同样有效的分子，可以在野生型植物中触发 PR-1 基因表达，但从野生型或 InsP 5-ptase 植物收集的渗出物在 InsP 5-ptase 植物中触发的 PR-1 基因表达较少。此外，表达谱表明，与野生型相比，InsP 5-ptase 植物中的几种防御基因，包括 PR-1、PR-2、PR-5 和 AIG1，基础表达水平下调。在受到病原体攻击时，这些基因在系统叶片中的表达要么没有被诱导，要么诱导延迟。我们的研究表明，磷脂酰肌醇信号是植物防御网络的一个组成部分，参与基础和系统反应。InsP3 介导的信号转导的减弱会影响 Ca2+释放、调节防御基因表达，并损害植物的防御反应。
