CLE effector peptide signaling in plant-nematode interactions

预计到2050年，全球人口将达到90亿，而植物寄生线虫是应对这一挑战的主要障碍。这些线虫每年在全世界造成数十亿美元的产量损失。由于商业上可接受的抗性品种的缺乏或遗传基础有限，线虫田间种群的基因型变异以及新物种的出现，这类农业上重要的害虫对作物生产构成持续威胁。经济上最重要的植物寄生线虫包括囊状线虫。囊线虫通过在植物根部建立一个永久的取食点，与植物宿主形成寄生关系，作为营养汇，支持线虫的生长发育。该项目将为植物如何识别和响应线虫分泌的分子，从而在寄主根部形成独特和必需的摄食细胞提供新的见解，这可能反过来转化为生物工程作物的新策略，使其对致病性囊肿线虫具有强大的抗性。研究人员试图了解植物寄生性囊线虫在寄主发育过程中共同选择摄食细胞形成的详细分子机制和途径。摄食细胞的发育和维持依赖于囊线虫食道腺细胞中产生的花柱分泌效应蛋白。然而，我们对线虫分泌的效应物指导宿主细胞转化过程的信号传导过程的理解在很大程度上是缺乏的。花柱分泌效应物中有与植物CLAVATA3/胚乳周围区域相关（CLE）肽相似的小信号肽。研究人员已经证明，这些线虫分泌的肽信号是成功感染所必需的，但它们在根细胞发育重编程以形成喂养细胞中的确切作用尚不清楚。该项目的重点是阐明线虫分泌的CLE肽在调节植物细胞程序中的功能，以喂养细胞形成。分子，遗传，基因组学和生化分析将用于表征线虫CLE肽在喂养细胞形成中的作用。一旦进入宿主细胞，CLE蛋白通过一种新的翻译后转运机制被重定向到外质体。转运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。在外质体中，CLE肽被植物受体感知。受体定位将被表征，缺失和诱变研究将用于评估受体对线虫CLE肽的结合特异性。CLE肽调节植物激素和防御信号通路的假设将通过突变体、报告系和其他相关试验（包括线虫感染试验和体外肽应用试验）的细胞特异性研究来验证。所产生的数据将提供关于一类植物寄生囊肿线虫特有的病原体效应物的信息，以及病原体分泌植物肽激素的蛋白质模拟物的第一个例子。除了囊线虫与植物的相互作用之外，所产生的数据将有助于理解CLE信号和植物中潜在的新型蛋白质运输途径。该项目将把研究活动与女性和少数民族本科生在植物分子遗传学和细胞生物学方面的教育和培训结合起来，通过针对小学五年级的外展项目，重点关注植物科学和技术的社会应用。

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.