Plant-Plant Signaling in the Rhizosphere: the Role of Quinone Oxidoreductases in Host Perception by Parasitic Plants

根际植物间信号传导：醌氧化还原酶在寄生植物宿主感知中的作用

• 批准号: 9983053
• 负责人: John Yoder
• 金额: $ 30万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-01 至 2003-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9983053&HistoricalAwards=false
• 关键词: Plant; Signaling; Rhizosphere; Role; Quinone

Plants identify nearby plants by perceiving chemical signals released by roots into the soil. Parasitic plants in the family Scrophulariaceae recognize quinone molecules released by the roots of host plants to trigger the development of haustoria, parasite-specific root organs that function in host attachment and invasion. Haustorium induction and development is readily monitored in vitro by applying host root exudates or purified haustoria inducing factors (HIFs) onto roots of aseptic parasite seedlings. Because haustorium development is rapid, highly synchronous and strictly dependent on exogenous HIFs, it is a fantastic system for investigating molecular mechanisms governing subterranean plant-plant interactions.It is likely that a common redox reaction occurring between structurally diverse HIFs and a parasite receptor initiates the haustorium development signal pathway. Two quinone oxidoreductases have been cloned from the parasitic plant Triphysaria that have properties consistent with them being directly involved in the perception and initial processing of the HIF 2,6-dimethoxybenzoquinone (DMBQ). Based on sequence and structural homologies with well characterized proteins in microbes, fungi and vertebrates, TvQR1 and TvQR2 likely encode different NAD(P) dependent quinone oxidoreductases. TvQR1 is homologous to a family of oxidoreductases that catalyze one-electron quinone reductions, yielding the semiquinone intermediate predicted to be critical in HIF signal transduction. In contrast, TvQR2 is homologous to a detoxifying quinone oxidoreductase that catalyzes two electron reductions, thus bypassing the semiquinone intermediate. These experiments will test the hypothesis that TvQR1 and TvQR2 catalyze distinct reactions fulfilling different biological functions.Both TvQR1 and TvQR2 are primary response genes transcriptionally activated in Triphysaria by DMBQ in the absence of de novo protein synthesis. Promoter sequences responsible for DMBQ responsiveness will be identified by assaying reporter fusions in transgenic Arabidopsis. Sequence comparisons of TvQR1 promoters in parasitic and non-parasitic plants will elucidate the mechanism of parasite specific responsiveness. Because TvQR2 is predicted to cleanse the cells of oxidized quinones used by TvQR1 as HIF substrates, the relative levels of these two enzymes in parasite roots is predicted to determine HIF responsiveness. Western blots probed with TvQR1 and TvQR2 specific antibodies will determine if protein levels reflect transcript abundance. A comparison of protein levels and activities in DMBQ responsive and non-responsive lines will relate TvQR1 and / or TvQR2 to specialized functions in parasitic plants. By understanding the mechanisms that plants use to recognize and respond to other plants, it should be possible to engineer plants for optimal growth in the presence of weeds.

植物通过感知根部释放到土壤中的化学信号来识别附近的植物。玄参科的寄生植物识别寄主植物根系释放的醌分子，从而触发吸器的发育，这是寄生虫特有的根系器官，在寄主附着和入侵中起作用。通过将寄主根系分泌物或纯化的吸器诱导因子（hif）施用于无菌寄生虫幼苗的根部，可以很容易地在体外监测吸器的诱导和发育。由于吸器发育迅速、高度同步且严格依赖外源hif，因此它是研究地下植物-植物相互作用分子机制的绝佳系统。很可能在结构不同的hif和寄生虫受体之间发生的共同氧化还原反应启动了吸器发育信号通路。从寄生植物三绒藻中克隆出两个醌氧化还原酶，其性质与直接参与HIF 2,6-二甲氧基苯醌（DMBQ）的感知和初始加工相一致。基于与微生物、真菌和脊椎动物中已被充分表征的蛋白质的序列和结构同源性，TvQR1和TvQR2可能编码不同的NAD(P)依赖的醌氧化还原酶。TvQR1与一个氧化还原酶家族同源，该家族催化单电子醌还原，产生半醌中间体，预计在HIF信号转导中至关重要。相反，TvQR2与一种解毒醌氧化还原酶同源，该酶催化两次电子还原，从而绕过半醌中间体。这些实验将验证TvQR1和TvQR2催化不同反应实现不同生物学功能的假设。TvQR1和TvQR2都是在没有新生蛋白合成的情况下由DMBQ转录激活的主要应答基因。负责DMBQ响应性的启动子序列将通过分析转基因拟南芥的报告基因融合来确定。比较寄生植物和非寄生植物中TvQR1启动子的序列将有助于阐明寄生虫特异性应答的机制。由于预计TvQR2可以清除细胞中被TvQR1用作HIF底物的氧化醌，因此预计这两种酶在寄生虫根中的相对水平可以确定HIF反应性。Western blots检测的TvQR1和TvQR2特异性抗体将确定蛋白水平是否反映转录物的丰度。比较DMBQ响应系和非响应系的蛋白水平和活性将使TvQR1和/或TvQR2与寄生植物的特殊功能联系起来。通过了解植物用来识别和响应其他植物的机制，应该有可能在杂草存在的情况下设计植物以实现最佳生长。