(1st Place) Modifying phytosterol production in upland cotton reduces the performance of insect herbivores

Sterols are essential micronutrients that play fundamental roles in eukaryotic cells and physiology. Insects have lost the ability to synthesize sterols de novo and must derive them from their diet. Cholesterol is the dominant insect sterol and precursor to many ecdysteroids. Contrary to insect predators, herbivores have cholesterol-limited diets because most plants produce insignificant amounts of cholesterol. Instead, plants produce phytosterols that must be metabolized to cholesterol during digestion. Exploiting this metabolic constraint by interfering with phytosterol metabolism was explored as a potential pest management strategy. Virus-induced gene silencing (VIGS) was used to modify phytosterol biosynthesis in Upland cotton by transiently silencing an Arabidopsis hyd1 ortholog. Previous studies silencing hyd1 in Arabidopsis showed shifts in phytosterol ratios and the accumulation of delta-8 phytosterols that negatively impacted the performance of chewing and piercing-sucking insects. Insects showed similarly reduced performance when reared on hyd1-silenced cotton plants. We suggest that interfering with phytosterol metabolism is a potential method for controlling insect pests and can be achieved using genetic engineering technologies for long-term crop protection.