title: Photoperiodic induction of diapause requires regulated transcription of timeless in the larval brain of Chymomyza costata.
abstract: Photoperiodic signal stimulates induction of larval diapause in Chymomyza costata. Larvae of NPD strain (npd-mutants) do not respond to photoperiod. Our previous results indicated that the locus npd could code for the timeless gene and its product might represent a molecular link between circadian and photoperiodic clock systems. Here we present results of tim mRNA (real time-PCR) and TIM protein (immunohistochemistry) analyses in the larval brain. TIM protein was localized in 2 neurons of each brain hemisphere of the 4-d-old 3rd instar wild-type larvae. In a marked contrast, no TIM neurons were detected in the brain of 4-day-old 3rd instar npd -mutant larvae and the level of tim transcripts was approximately 10-fold lower in the NPD than in the wild-type strain. Daily changes in tim expression and TIM presence appeared to be under photoperiodic control in the wild-type larvae. Clear daily oscillations of tim transcription were observed during the development of 3rd instars under the short-day conditions. Daily oscillations were less apparent under the long-day conditions, where a gradual increase of tim transcript abundance appeared as a prevailing trend. Analysis of the genomic structure of tim gene revealed that npd-mutants carry a 1855 bp-long deletion in the 5'-UTR region. This deletion removed the start of transcription and promoter regulatory motifs E-box and TER-box. The authors hypothesize that this mutation was responsible for dramatic reduction of tim transcription rates, disruption of circadian clock function, and disruption of photoperiodic calendar function in npd-mutant larvae of C. costata.
authors: Institute of Entomology, Biology Centre AS CR, Ceske Budejovice, Czech Republic.
authors: J
authors: J
authors: Stehlík
authors: R
authors: R
authors: Závodská
authors: K
authors: K
authors: Shimada
authors: I
authors: I
authors: Sauman
authors: V
authors: V
authors: Kostál
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology; D018428:Drosophilidae / Q000502:physiology*; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007814:Larva / Q000166:cytology / Q000378:metabolism; D008018:Life Cycle Stages; D017440:Photoperiod; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D019476:Insect Proteins; D012333:RNA, Messenger