Differential gene expression in Helicoverpa zea provides new insights in phytosterol metabolism

Cholesterol is used in biomembranes and as a precursor to molting hormones in insects. However, insects are unable to synthesize sterols (including cholesterol) de novo and thus acquire sterols from dietary sources. Predacious and scavenger insects often acquire their dietary cholesterol directly as it is abundant in insect tissues. On the other hand, plant-feeding insects acquire limited dietary cholesterol because plants produce it in negligible quantities. Instead, plants commonly produce alkylated sterols (i.e. phytosterols) that plant-feeding insects convert to cholesterol through a dealkylation pathway. Dealkylation is well documented insofar as the intermediates of the conversion process have been identified in model species. However, there remains a significant knowledge gap in our understanding of the key enzymes involved in dealkylation. To that end, we conducted an RNA-Seq experiment to identify differentiated expressed genes associated with phytosterol metabolism in the generalist insect Helicoverpa zea. Our results suggest that subtle differences in dietary sterols have influential impacts on gene expression beyond phytosterol metabolism in a short period of time.