Neral (the Alarm Pheromone) Biosynthesis via the Mevalonate Pathway, Evidenced by D-Glucose-1-¹³C Feeding in Carpoglyphus lactis and ¹³C Incorporation into Other Opisthonotal Gland Exudates

Abstract

The monoterpene neral [(Z)-3,7-dimethyl-2,6-octadienal], an alarm pheromone, has been identified as a major component of the opisthonotal gland exudates of Carpoglyphus lactis, together with tridecane and (Z,Z)-6,9-heptadecadiene. The CDCl₃ extract of mites fed D-glucose-1-¹³C for 30 days was found to have ¹³C atoms at positions 2, 4, 6 and 8–10 by ¹³C-NMR analysis. The compound neral was, therefore, concluded to be produced via the mevalonate pathway from 2-¹³C-acetyl-CoA by glycolysis. After seven days of feeding on D-glucose-1-¹³C, at least one ¹³C atom was incorporated in 51.6% of neral molecules. Likewise, 51.8% of tridecane, 42.5% of (Z,Z)-6,9-heptadecadiene, 39.5% of γ-acaridial and 33.4% of neryl formate, were also labeled, while squalene was not labeled, indicative of its origin, the culture medium.