Suppression of Oocyte Development by a Trehalase Inhibitor, Validoxylamine A, through Inhibition of Juvenile Hormone Biosynthesis and Vitellogenesis in the Migratory Locust, Locusta migratoria L.

Validoxylamine A (VAA) is a highly specific trehalase inhibitor and its administration to insects results in accumulation of trehalose in their body. In the migratory locust, Locusta migratoria, this compound suppressed oocyte development when injected to reproductively active females. Most individuals injected with VAA stopped oocyte development completely after producing a few egg-pods, whereas water-injected controls continued to lay eggs until they died. VAA did not influence longevity of females unless a large dose (100μg/animal) was given. JH biosynthetic activity in vitro was 18.8 pmol/h/pair on average for corpora allata (CA) taken from water-injected females, whereas it was only 1.01 pmol/h for those removed from VAA-injected females, in spite of the fact that the culture medium used contained a large amount of glucose, the metabolic fuel normally produced from trehalose by the action of trehalase. It seems that the reduced activity by CA from VAA-injected females was brought about by reduced amounts of precursors, because an addition of a precursor, farnesol, to the medium restored the function of such CA. Topical application of a JH analog, methoprene, stimulated oocyte growth in reproductively inactive females injected with water, but failed to do so in those injected with VAA. However, in vitro incubation of fat body with labelled methionine indicated that JHA stimulated vitellogenenin synthesis both in VAA-injected and water-injected females, though protein synthesis appeared to be less active in the former. SDS-PAGE profiles of hemolymph samples also confirmed the presence of various proteins including vitellogenins in the two groups of locusts. These results apparently suggest that VAA suppressed oocyte development in this species through affecting JH biosynthesis by CA, vitellogenin synthesis by the fat body, and uptake of yolk material by the ovary.