CLE effector peptide signaling in plant-nematode interactions

植物寄生线虫是应对养活预计到2050年将达到90亿人口的挑战的主要障碍。这些线虫每年在全球造成数十亿美元的产量损失。商业上可接受的抗性品种的缺乏或遗传基础有限，田间线虫种群的基因变异性，以及新物种的出现，对这类农业重要害虫的作物生产构成了持续的威胁。经济上最重要的植物寄生线虫包括形成包囊的线虫。孢囊线虫通过在根部建立一个永久的取食部位，作为支持线虫生长和发育的营养库，与植物宿主形成寄生关系。该项目将为植物如何识别和响应线虫分泌的分子以在宿主根中形成独特和必要的摄食细胞提供新的见解，这反过来可能转化为生物工程作物的新策略，使其对致病胞囊线虫具有强大的抗性。研究人员试图了解植物寄生孢囊线虫共同选择寄主发育程序以形成摄食细胞的详细分子机制和途径。摄食细胞的发育和维持依赖于孢囊线虫食管腺细胞中产生的口针分泌的效应蛋白。然而，我们对线虫分泌的效应器引导宿主细胞转化过程的信号过程的了解很少。在口针分泌的效应物中，有一些小信号肽与植物CLAVATA3/胚乳周围区域相关肽(CLE)有相似之处。研究人员已经证明，这些线虫分泌的多肽信号是成功感染所必需的，但它们在根细胞发育重新编程以形成摄食细胞方面的确切作用尚不清楚。该项目的重点是阐明线虫分泌的CLE多肽在调节植物细胞程序中的功能，以形成摄食细胞。分子、遗传、基因组和生化分析将被用来描述线虫CLE多肽在摄食细胞形成中的作用。一旦被送入宿主细胞，CLE蛋白就通过一种新的翻译后转运机制被重定向到质外体。运输途径将通过亚细胞定位和宿主相互作用蛋白的分析来研究。在质外体中，CLE多肽被植物受体感知。将确定受体定位，并将使用缺失和突变研究来评估线虫CLE多肽的受体结合特异性。CLE多肽调节植物激素和防御信号通路的假说将通过对突变体、报告系和其他相关测试的细胞特异性研究来验证，包括线虫感染测试和体外多肽应用测试。产生的数据将提供关于植物寄生孢囊线虫特有的一类病原体效应器的信息，以及第一个病原体分泌模拟植物多肽激素的蛋白质的例子。除了孢囊线虫与植物的相互作用外，产生的数据将有助于理解CLE信号和潜在的植物中新的蛋白质运输途径。该项目将通过针对K-5的推广计划，将研究活动与植物分子遗传学和细胞生物学方面的女性和代表性较低的少数族裔本科生的教育和培训结合起来，重点是植物科学和技术对社会的应用。

Plant-parasitic nematodes are a major impediment to meeting the challenge of feeding a population projected to reach 9 billion by 2050. These nematodes cause billions of dollars in yield losses annually worldwide. The unavailability or limited genetic base of commercially acceptable resistant cultivars, genotypic variability in nematode field populations, as well as the emergence of new species, pose a continued threat to crop production by this group of agriculturally important pests. The most economically important plant-parasitic nematodes include the cyst forming nematodes. Cyst nematodes form parasitic relationships with their plant hosts by establishing a permanent feeding site within the root, which serves as a nutrient sink to support growth and development of the nematode. This project will provide new insights into how plants recognize and respond to nematode-secreted molecules to form unique and essential feeding cells within host roots, which may, in turn, translate into novel strategies to bioengineer crops with robust resistance to pathogenic cyst nematodes. The investigators seek to understand the detailed molecular mechanisms and pathways by which plant-parasitic cyst nematodes co-opt host developmental programs for feeding cell formation. Feeding cell development and maintenance is dependent on stylet-secreted effector proteins produced in the esophageal gland cells of cyst nematodes. However, our understanding of signaling processes directing the process of host cell transformation by nematode-secreted effectors is largely lacking. Among the stylet-secreted effectors are small signaling peptides sharing similarity with plant CLAVATA3/ENDOSPERM SURROUNDING REGION-related (CLE) peptides. The investigators have demonstrated that these nematode-secreted peptide signals are required for successful infection, but their exact role in developmental reprogramming of root cells for feeding cell formation remains unclear. The project focuses on elucidating the function of nematode-secreted CLE peptides in modulating the plant cellular program for feeding cell formation. Molecular, genetic, genomic, and biochemical analyses will be used to characterize the role of nematode CLE peptides in feeding cell formation. Once delivered into host cells, CLE proteins are retargeted to the apoplast via a novel post-translational trafficking mechanism. The trafficking pathway will be investigated through subcellular localization and analyses of host-interacting proteins. In the apoplast, CLE peptides are perceived by plant receptors. Receptor localization will be characterized and deletion and mutagenesis studies will be used to evaluate receptor binding specificity to nematode CLE peptides. The hypothesis that CLE peptides act to modulate phytohormone and defense signaling pathways will be tested through cell-specific studies of mutants, reporter lines, and other related assays including nematode infection assays and in vitro peptide application assays. The data generated will provide information about a class of pathogen effectors unique to plant-parasitic cyst nematodes and the first example of a pathogen secreting a protein mimic of a plant peptide hormone. Beyond the cyst nematode-plant interaction, the data generated will contribute to an understanding of CLE signaling and potentially novel protein trafficking pathways in plants. The project will integrate research activities with education and training of female and underrepresented minority undergraduate students in plant molecular genetics and cell biology through outreach programs targeting K-5 focused on applications of plant science and technology for society.