The Fall Armyworm Functional Genomics: Genome Editing and RNAi

Agricultural losses due to arthropod pests continue to grow despite the application of approximately three million tons of pesticides worth $40 billion worldwide each year. Development of novel and environmentally friendly pest management methods are urgently needed to meet the global challenge of sustained agricultural production with reduced pesticide use. The fall armyworm (FAW), Spodoptera frugiperda is a polyphagous pest that causes economic losses to many crops including corn, cotton, rice, apples, oranges and many vegetables in Americas and Caribbean countries. Because of its voracious feeding on many plants, year-round breeding and highly efficient detoxification system to cope with plant toxins and insecticides, this pest is becoming a major concern around the world. FAW belongs to the family, Noctuidae and the best lepidopteran model insect, the silkworm, Bombyx mori belongs to the family, Bombycidae, these families are thought to have diverged about 95 million years ago. Also, the silkworm is a monophagous insect whereas, FAW is a polyphagous insect. Therefore, we need to develop resources to study the molecular basis of biological processes that make this insect successful in causing crop losses despite our best efforts to control this devastating pest. Both genome and transcriptome sequences for FAW as well as for a cell line derived from this insect have been completed. However, functional genomics studies, as well as research to understand various developmental and physiological processes at the molecular level, are not performed in this insect. One of the main reasons for the lack of information on functional genomics in this insect is due to its recalcitrance to RNA interference (RNAi). RNAi is inefficient in this insect because double-stranded RNases (dsRNases) rapidly degrade double-stranded RNA (dsRNA) fed or injected into this insect. Also, some of the dsRNA entering the cells is entrapped in the endosomes, and some of the critical genes (e.g., StaufenC) required for efficient RNAi are not present in this insect. Genome editing technologies, especially the CRISPR/Cas method may help to overcome these problems and bring research on FAW to functional genomics era. Preliminary experiments in our laboratory showed that FAW eggs are relatively easy to inject and CRISPR/Cas9–based genome editing technique works in this insect. The major goal of this proposal is to develop the CRISPR/Cas9-based genome editing method for use by the scientific community working on this and other important lepidopteran pest insects. This goal will be achieved by conducting experiments under two objectives.