D3130: Linking 9-lipoxygenase enzymes to WCR resistance

The western corn rootworm (WCR), Diabrotica virgifera virgifera is a devastating pest of maize (Zea mays) in the United States and is responsible for over $1 billion in control costs and yield losses, annually. While traditional plant breeding programs have developed tolerant maize varieties, little is known about the specific mechanisms responsible for plant resistance and tolerance. This highlights a critical need to determine the natural enzymes and their products that may facilitate maize resistance to WCR to advance modern breeding methods as well as our understanding of maize insect defense. 

Through this study, we characterized potential role  of nearly identical 9-lipoxygenases lipoxygenase 4 (LOX4) and lipoxygenase 5 (LOX5) genes in maize resistance to WCR. We recently showed that LOX5 is required for resistance to aboveground herbivores such as fall armyworms due to its role in the synthesis of a 9-LOX-derived ketol, 9,10-KODA. By utilizing both single and double mutants, our goal was to investigate these enzymes and their products in terms of insect performance, survival and development speed as well as plant metabolite profile and root and shoot growth in response to herbivory. We found that transposon-insertional disruption of LOX4 and LOX5 leads to larger larvae with their double mutant (lox4lox5) increasing overall larvae survival. Root phenotypes were not affected by mutation and all genotypes suffered similar root damage. We suspect that this is due to reduced ketol production. Further studies need to be conducted to identify the specific ketol responsible for these phenotypic changes.