Juvenile hormone regulation of gene expression in the female reproduction of African migratory locusts, Locusta migratoria

Although juvenile hormone (JH) has essential roles in insect development and reproduction, the molecular mechanisms of gene regulation by JH remain an enigma. Locusta migratoria represents a suitable organism to conduct these studies. As the locust adult female matures, the JH titer rises and the fat body produces vitellogenins or yolk proteins. One fat body gene that is regulated by JH, jhp21, contains a partially palindromic 15-nt sequence, GAGGTTCGAGA/_TCCT T/_C, designated as a putative juvenile hormone response element (JHRE). The binding of a dephosphorylated protein (a transcriptional factor) to this DNA depended on an inverted repeat with GAGGTTC in the left half-site and a single nucleotide spacer in the JHRE as well as JH treatment of the locust. To identify the transcriptional factor yeast one-hybrid experiments using JHRE as “bait” were undertaken. Of four putative proteins, only one designated as 65.3 was soluble after bacterial expression and bound JHRE in electrophoretic mobility shift experiments. The presence of JH may stimulate the association of pre-existing proteins, including 65.3, to form an active protein complex, which binds to JHREs in the upstream region of JH-responsive genes and consequently regulates their transcription.; Two other JH-influenced sequences, encoding the α and γ subunits of the translation elongation factor-1 (EF-1) have been cloned and sequenced. The developmental expression of EF-1α and - 1γ, both single copy genes, paralleled reported changes in the hemolymph JH titer in the fifth instar and were elevated during early reproductive maturation in the female adult. The levels of both transcripts were also greatly increased by an enriched diet, previously shown to elevate JH titers and accelerate vitellogenin production as well as by the experimental treatment of JH-deprived adult females with the JH analog, methoprene. I suggest that production of elongation factors, increased by JH, may contribute to the massive protein synthesis required for egg production.; These studies taken together, increase our understanding of the complexity of JH regulation during the maturing of these insects.