Interaction of ML1 and SRB1-12 mediates cholesterol transport in the brown planthopper

Cholesterol transport plays a pivotal role in maintaining sterol homeostasis within eukaryotic cells. In mammals, Niemann-Pick Type C (NPC) proteins are known to participate in cholesterol transport. However, the precise pathways remain largely unexplored in insects. Here, we reported ML1, a lipid-recognition protein in a rice pest Nilaparvata lugens, specifically bound cholesterol. In addition, we identified a scavenger receptor class B Type Ⅰ (SRB1-12) protein as the receptor for ML1. SRB1-12 was predominantly expressed in the integument and regulated cuticular chitin biosynthesis and lipid metabolism in nymphs to ensure molting success. ML1 delivered cholesterol to SRB1-12 and supplied the steroid precursor for 20E biosynthesis, as reflected by altered whole-body 20E titers. ML1 and SRB1-12 co-regulated the expression of a newly identified gene MLSR, which played important roles in nymphal development and egg hatching. This study establishes a pathway of cholesterol trafficking within tissues and deepens the understanding of sterol homeostasis in insects.