RUI: Regulation of natural variation in maize (Zea mays) defense responses by jasmonate signaling

Each year, global agriculture suffers significant yield losses due to attack by insect pests. The United States is estimated to lose 25-30% of its agricultural production to insect attack, while estimates for tropical countries are as high as 50%. Damage from insect feeding and implementation of methods to reduce this damage cost American farmers about $40 billion annually. However, all plants have varying levels of natural protection against insect herbivory, including both mechanical barriers such has hairs and thorns and chemical defenses that deter or kill insect pests. Additionally, plants can emit volatile signals to recruit predators that consume the attacking insects. Although some defenses are always present, others are turned on only when the plants detect insect feeding. This defense induction is orchestrated by a hormone signaling pathway that is highly conserved in the plant kingdom. The proposed research is focused on identifying and investigating novel components of the defense signaling pathway in maize, the most important food crop in the United States. The identification of natural variation in the resistance of maize to insect feeding will provide new opportunities for breeding plants that are more pest tolerant. In addition, the project will provide authentic research experiences to undergraduate students, including students from groups that are underrepresented in science. A proposed outreach component of the project will expose the broader community to research on plant-insect interactions.<br/> <br/>The jasmonic acid signaling cascade, which regulates the transcriptomic responses of plants to insect attack, influences the expression of thousands of genes. Despite the global importance of maize (Zea mays) as a crop species and the critical role of jasmonates in regulating plant defense responses, the maize jasmonic acid signaling cascade remains relatively uninvestigated compared to the corresponding pathways in well-studied model plant species such as Arabidopsis and tomato. Considering the evolutionary distance between these model dicots and maize, it is reasonable to expect distinct jasmonic acid regulatory mechanisms in the defense responses of this economically important monocot species. An integrated systems biology approach, involving transcriptomic, metabolomic, and genetic methods, will be used to uncover and characterize novel aspects of defense regulation in maize. A genetically diverse population of maize inbred lines will be used to assess natural variation in the accumulation of herbivore-induced jasmonate and jasmonate-like molecules, identify previously unknown regulators of defense responses, and elucidate their roles in maize defense against two lepidopteran pests, fall armyworms (Spodoptera frugiperda) and beet armyworms (Spodoptera exigua). In addition to providing the scientific community with insight into the regulation of defense responses in maize, the planned studies will generate high-quality transcriptomic and metabolomic data sets that will enable other researchers to conduct further investigations of natural variation in maize defense responses. A graduate student and a postdoc will receive research training and will gain mentoring experience by helping to supervise the experiments of undergraduate students contributing on this project.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.