@article {2504, title = {Kr{\"u}ppel homolog 1 (Kr-h1) mediates juvenile hormone action during metamorphosis of Drosophila melanogaster.}, journal = {Mechanisms of Development}, volume = {125}, year = {2008}, month = {2008 Jan-Feb}, pages = {91-105}, abstract = {

Juvenile hormone (JH) given at pupariation inhibits bristle formation and causes pupal cuticle formation in the abdomen of Drosophila melanogaster due to its prolongation of expression of the transcription factor Broad (BR). In a microarray analysis of JH-induced gene expression in abdominal integument, we found that Kr{\"u}ppel homolog 1 (Kr-h1) was up-regulated during most of adult development. Quantitative real-time PCR analyses showed that Kr-h1 up-regulation began at 10h after puparium formation (APF), and Kr-h1 up-regulation occurred in imaginal epidermal cells, persisting larval muscles, and larval oenocytes. Ectopic expression of Kr-h1 in abdominal epidermis using T155-Gal4 to drive UAS-Kr-h1 resulted in missing or short bristles in the dorsal midline. This phenotype was similar to that seen after a low dose of JH or after misexpression of br between 21 and 30 h APF. Ectopic expression of Kr-h1 prolonged the expression of BR protein in the pleura and the dorsal tergite. No Kr-h1 was seen after misexpression of br. Thus, Kr-h1 mediates some of the JH signaling in the adult abdominal epidermis and is upstream of br in this pathway. We also show for the first time that the JH-mediated maintenance of br expression in this epidermis is patterned and that JH delays the fusion of the imaginal cells and the disappearance of Dpp in the dorsal midline.

}, keywords = {Animals, Base Sequence, Biological, DNA Primers, Drosophila melanogaster, Drosophila Proteins, Kruppel-Like Transcription Factors, Larva, Metamorphosis, Oligonucleotide Array Sequence Analysis, Polymerase Chain Reaction, Up-Regulation}, issn = {0925-4773}, doi = {10.1016/j.mod.2007.10.002}, author = {Minakuchi, Chieka and Zhou, Xiaofeng and Riddiford, Lynn M} } @article {2513, title = {Overexpression of broad: a new insight into its role in the Drosophila prothoracic gland cells.}, journal = {The Journal of Experimental Biology}, volume = {207}, year = {2004}, month = {2004 Mar}, pages = {1151-61}, abstract = {

Insect molting is triggered by ecdysteroids, which are produced in the prothoracic glands (PG). The broad (br) gene is one of the {\textquoteright}early genes{\textquoteright} directly regulated by ecdysteroids. Ectopic expression of the BR-Z3 isoform in early second instar Drosophila larvae (L2) before the rise of the ecdysteroid titer prevented molting to the third instar, but the larvae subsequently formed L2 prepupae after prolonged feeding. When these larvae were fed on diet containing 20-hydroxyecdysone (20E), they formed pharate third instar larvae. The critical weight for normal L3 pupariation of w(1118) larvae was found to be 0.8 mg and that for L2 pupariation was 0.45 mg. We also defined a threshold weight for metamorphosis of 0.3 mg, above which L2 larvae will metamorphose when provided with 20E. BR-Z3 apparently works through the PG cells of the ring gland but not the putative neurosecretory cells that drive ecdysone secretion, because ectopic expression of BR-Z3 specifically in the ring gland caused 53\% of the larvae to become permanent first instar larvae. Driving other BR isoforms in the ring gland prevented larval molting or pupariation to varying degrees. These molting defects were rescued by feeding 20E. Overexpression of each of the BR isoforms caused degeneration of the PG cells but on different time courses, indicating that BR is a signal for the degeneration of the PG cells that normally occurs during the pupal-adult transition.

}, keywords = {Animals, Body Weights and Measures, Drosophila, Drosophila Proteins, Ecdysterone, Exocrine Glands, Gene Expression Regulation, Genetically Modified, Immunohistochemistry, Larva, Molting, Protein Isoforms, Transcription Factors}, issn = {0022-0949}, author = {Zhou, Xiaofeng and Zhou, Baohua and Truman, James W and Riddiford, Lynn M} } @article {2515, title = {Broad specifies pupal development and mediates the {\textquoteright}status quo{\textquoteright} action of juvenile hormone on the pupal-adult transformation in Drosophila and Manduca.}, journal = {Development }, volume = {129}, year = {2002}, month = {2002 May}, pages = {2259-69}, abstract = {

The understanding of the molecular basis of the endocrine control of insect metamorphosis has been hampered by the profound differences in responses of the Lepidoptera and the Diptera to juvenile hormone (JH). In both Manduca and Drosophila, the broad (br) gene is expressed in the epidermis during the formation of the pupa, but not during adult differentiation. Misexpression of BR-Z1 during either a larval or an adult molt of Drosophila suppressed stage-specific cuticle genes and activated pupal cuticle genes, showing that br is a major specifier of the pupal stage. Treatment with a JH mimic at the onset of the adult molt causes br re-expression and the formation of a second pupal cuticle in Manduca, but only in the abdomen of Drosophila. Expression of the BR isoforms during adult development of Drosophila suppressed bristle and hair formation when induced early or redirected cuticle production toward the pupal program when induced late. Expression of BR-Z1 at both of these times mimicked the effect of JH application but, unlike JH, it caused production of a new pupal cuticle on the head and thorax as well as on the abdomen. Consequently, the {\textquoteright}status quo{\textquoteright} action of JH on the pupal-adult transformation is mediated by the JH-induced re-expression of BR.

}, keywords = {Animals, Developmental, Drosophila, Gene Expression Regulation, Genes, Insect, Juvenile Hormones, Manduca, Messenger, Protein Isoforms, Pupa, RNA, Species Specificity}, issn = {0950-1991}, author = {Zhou, Xiaofeng and Riddiford, Lynn M} }