Genomics of Resistance to Mite Herbivores Associated with Drought Stress in Cereals

害虫造成的作物损失，包括毛虫或蚜虫等动物，对可持续农业实践提出了重大挑战。在以植物组织为食的食草动物中，昆虫是迄今为止最具特色的。然而，作为昆虫远亲的植物饲养螨也可能是农业中的主要害虫。特别是，许多螨类物种在干旱胁迫的植物上茁壮成长并破坏干旱胁迫的植物，包括玉米和小麦等主要谷类作物。在这些情况下，螨对控制构成了重大挑战，因为它们通常对常用的农药具有抗性。植物可以保护自己免受食草动物的攻击和破坏。 例如，对于许多植物物种，已知某些品种比其他品种更能抵抗螨虫，因为它们能够产生对食草动物有毒的化合物。本研究的目的是了解植物防御途径的遗传和基因组性质，以阻止农业上重要的螨。要检查的螨种是二斑叶螨（二斑叶螨）和银行草螨（草地小爪螨），与干旱胁迫玉米或其他谷物物种的重大爆发。这项研究将使用基因组和遗传方法来阐明玉米（Zea mays ssp.）mays）和大麦（Hordeum vulgare L.）响应螨植食性，以及这些途径的变化如何影响植物的抗性。此外，将评估干旱（水分胁迫）对这些防御途径的影响，这一目标的动机是观察到这些害虫中的每一种在干旱期间都可能造成经济损失。因此，该项目与开发更多抗螨作物的努力有关。所有数据都将通过基因表达综合数据库（GEO）和玉米数据库（MaizeGDB）等长期公共数据库向公众开放。项目期间产生的生物资源将应要求提供。作为该项目的一部分，这项工作将培训本科生、研究生和研究生学者。 此外，还将编写关于植物与螨相互作用的教育材料，在Learn.Genetics网站（http：//learn.genetics.utah.edu/）上向公众分发。为了确定植物对叶螨害虫作出反应的遗传途径，将在受双斑叶螨（双子叶植物和单子叶植物上的通才害虫）和班克斯草螨（禾本科植物上的专门害虫）侵染的玉米和大麦叶片上使用RNA-seq方法（cDNA的高通量测序）进行基因表达谱分析。此外，为了理解农业上重要的非生物胁迫对植物防御途径的影响，将在充分浇水和水胁迫的植物上进行螨响应的表达谱分析。比较植物的转录反应的两种食草动物，并作为一个功能的非生物胁迫有关螨爆发，将揭示植物反应的特异性，以通才和专家食草动物，以及环境如何影响植物的相互作用。一个具体的结果将是确定螨抗性的基因调控网络。此外，已知对螨损害的易感性在植物物种（包括玉米）内的个体之间变化。为了研究这一点，将筛选用于创建巢式关联作图（NAM）社区遗传作图资源的近交玉米品系的集合，以确定对每种螨类食草动物的易感性或抗性。敏感和抗性玉米品系的基因表达研究将用于评估植物抗螨性变异的基因组基础。平行地，并且为了将螨响应的植物分子表型与农业环境中螨侵染后的植物性能相关联，将在玉米近交系的子集的高水和干旱胁迫条件下对植物进行抗性的田间试验。

Crop losses to pests, including animals like caterpillars or aphids, present a major challenge for sustainable agricultural practices. Among herbivores that feed on plant tissues, insects are by far the best characterized. However, plant-feeding mites, which are distant relatives of insects, can also be major pests in agriculture. In particular, many mite species thrive on and damage drought-stressed plants, including major cereal crops like maize and wheat. Under these situations, mites pose a significant challenge for control as they are often resistant to commonly used pesticides. Plants can defend themselves against attack and damage by herbivores. For example, for a number of plant species, certain varieties are known to be more resistant to mites than others because of their ability to produce compounds toxic to herbivores. The objective of this research is to understand the genetic and genomic nature of plant defense pathways that function to deter agriculturally important mites. The mite species to be examined are the two-spotted spider mite (Tetranychus urticae) and the Banks grass mite (Oligonychus pratensis) that are associated with significant outbreaks on drought-stressed maize or other cereal species. The research will use genomic and genetic methods to elucidate which plant defense pathways in maize (Zea mays ssp. mays) and barley (Hordeum vulgare L.) respond to mite herbivory, and how variation in these pathways impacts plant resistance. Moreover, the effect of drought (water stress) on these defense pathways will be assessed, an objective motivated by the observation that each of these pests can be economically damaging during droughts. This project has relevance, therefore, to efforts to develop more mite resistant crop plants. All data will be accessible to the public through long-term public repositories such as the Gene Expression Omnibus (GEO) and MaizeGDB. Biological resources generated during the project will be available upon request. As part of the project, the work will train undergraduate, graduate and post-graduate scholars. In addition, educational material will be developed on plant-mite interactions for distribution to the public on the Learn.Genetics website (http://learn.genetics.utah.edu/).To identify genetic pathways in plants that respond to spider mite pests, gene expression profiling using the RNA-seq method (high throughput sequencing of cDNA) will be performed on maize and barley leaves infested with both two-spotted spider mites (a generalist pest on both dicot and monocot plants) and Banks grass mites (a specialist pest on grasses). Further, to understand the effect of an agriculturally important abiotic stress on plant defense pathways, expression profiling for mite responses will be performed on both well watered and water stressed plants. Comparisons of plant transcriptional response to the two herbivores, and as a function of an abiotic stress relevant to mite outbreaks, will shed light on the specificity of plant responses to generalist and specialist herbivores, and how the environment affects the interaction in plants. A specific outcome will be the identification of gene regulatory networks underlying mite resistance. Further, susceptibility to mite damage is known to vary among individuals within plant species, including maize. To investigate this, a collection of inbred maize lines used to create the Nested Association Mapping (NAM) community genetic mapping resource will be screened for susceptibility or resistance to each mite herbivore. Gene expression studies with sensitive and resistant maize lines will then be used to assess the genomic basis of variation in plant mite resistance. In parallel, and to relate plant molecular phenotypes of mite response to plant performance upon mite infestation in an agricultural setting, field trials for resistance will be performed on plants under high water and drought stress conditions for a subset of maize inbred lines.