Yeast-like symbiotes as a sterol source in anobiid beetles (coleoptera, anobiidae): possible metabolic pathways from fungal sterols to 7-dehydrocholesterol

摘要

Insects are unable to synthesize and require exogenous sterol sources for their normal development and reproduction. A few exceptions are insects associated with symbiotic yeasts or fungi. We analyzed sterols by GC-MS in two anobiid beetles (Lasioderma serricorne and Stegobium paniceum), their intracellular yeast-like symbiotes (YLS), and their diets in order to darify the sterols synthesized by YLS and the metabolic pathways of the sterols in the beetles. Several C_(27), C_(28), C_(29) soturated and unsaturated sterols were identified; the predominant sterols were cholsterol and 7-dehydrocholesterol in the anobiid beetles and ergosterol in YLS. Most sterols detected in YLS were those known in the late pathway of the ergosterol biosynthesis in yeasts and most of the sterols in the beetles appear to be intermediate metabilites from YLS sterols to 7-dehydrocholesterol. The anobiid appear to use ergosterol and 5-dihydroergosterol as sources for 7-dehydrocholesterol.