The orphan nuclear receptors BmE75A and BmE75C of the silkmoth Bombyx mori: hornmonal control and ovarian expression.
The steroid hormone 20-hydroxyecdysone (20E) plays a key role in the stimulation of ovarian follicle development in the silkmoth, Bombyx mori. To understand better the mechanism by which 20E regulates silkmoth oogenesis, Bombyx homologs of the ecdysone-inducible orphan nuclear receptor E75 (BmE75) were cloned and their expression was analyzed in developing ovaries and staged follicles during metamorphosis. Of the two BmE75 isoforms isolated, only the A-isoform (BmE75A) has been identified previously in lepidopteran insects. BmE75C, on the other hand, shows significant sequence homology in its N-terminus to the Drosophila E75C isoform. Northern blot analysis shows unique expression patterns for each isoform mRNA during ovarian development. While the A-isoform seems to be mainly implicated in the earlier stages of the ecdysone response during previtellogenesis and vitellogenesis, expression of the C-isoform becomes strongly induced in an ecdysteroid-independent fashion at the transition from vitellogenesis to choriogenesis. Our data indicate a complex regulation of the expression of the BmE75 gene during oogenesis and postulate a new role for the BmE75C receptor at the end of vitellogenesis and the beginning of choriogenesis.
Swevers
L
L
Institute of Biology, National Centre for Scientific Research Demokritos, P.O. Box 60228, Aghia Paraskevi Attikis, 153 10 Athens, Greece.
Eystathioy
T
T
Iatrou
K
K
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx; D002823:Chorion / Q000502:physiology; D017931:DNA Primers; D005260:Female; D005786:Gene Expression Regulation; D007301:Insect Hormones; D008969:Molecular Sequence Data; D006080:Ovarian Follicle / Q000502:physiology; D010053:Ovary / Q000502:physiology; D016133:Polymerase Chain Reaction; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics*; D013045:Species Specificity
D017931:DNA Primers; D007301:Insect Hormones; D020033:Protein Isoforms; D018160:Receptors, Cytoplasmic and Nuclear