Drosophila-type timeless (dTIM) is a key clock protein in fruit flies, regulating rhythmicity and light-mediated entrainment. However, functional experiments indicate that its contribution to the clock differs in various insects. Therefore, we conducted a comprehensive phylogenetic analysis of dTIM across animals and dated its origin, gene duplications, and losses. We identified variable and conserved protein domains and pinpointed animal lineages that underwent the biggest changes in dTIM. While dTIM modifications are only mildly affected by changes in the PER protein, even the complete loss of PER in echinoderms had no impact on dTIM. However, changes in dTIM always co-occur with the loss of CRYPTOCHROMES or JETLAG. This is exemplified by the remarkably accelerated evolution of dTIM in phylloxera and aphids. Finally, alternative d-tim splicing, characteristic of Drosophila melanogaster temperature-dependent function, is conserved to some extent in Diptera, albeit with unique alterations. Altogether, this study pinpoints major changes that shaped dTIM evolution.

• Klíčová slova
• Evolutionary biology, Genetics, Molecular biology, Neuroscience,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: Diapause is a developmental alternative to direct ontogeny in many invertebrates. Its primary adaptive meaning is to secure survival over unfavourable seasons in a state of developmental arrest usually accompanied by metabolic suppression and enhanced tolerance to environmental stressors. During photoperiodically triggered diapause of insects, the ontogeny is centrally turned off under hormonal control, the molecular details of this transition being poorly understood. Using RNAseq technology, we characterized transcription profiles associated with photoperiodic diapause induction in the larvae of the drosophilid fly Chymomyza costata with the goal of identifying candidate genes and processes linked to upstream regulatory events that eventually lead to a complex phenotypic change. RESULTS: Short day photoperiod triggering diapause was associated to inhibition of 20-hydroxy ecdysone (20-HE) signalling during the photoperiod-sensitive stage of C. costata larval development. The mRNA levels of several key genes involved in 20-HE biosynthesis, perception, and signalling were significantly downregulated under short days. Hormonal change was translated into downregulation of a series of other transcripts with broad influence on gene expression, protein translation, alternative histone marking by methylation and alternative splicing. These changes probably resulted in blockade of direct development and deep restructuring of metabolic pathways indicated by differential expression of genes involved in cell cycle regulation, metabolism, detoxification, redox balance, protection against oxidative stress, cuticle formation and synthesis of larval storage proteins. This highly complex alteration of gene transcription was expressed already during first extended night, within the first four hours after the change of the photoperiodic signal from long days to short days. We validated our RNAseq differential gene expression results in an independent qRT-PCR experiment involving wild-type (photoperiodic) and NPD-mutant (non-photoperiodic) strains of C. costata. CONCLUSIONS: Our study revealed several strong candidate genes for follow-up functional studies. Candidate genes code for upstream regulators of a complex change of gene expression, which leads to phenotypic switch from direct ontogeny to larval diapause.

• MeSH
• Drosophilidae embryologie   genetika   MeSH
• genetická transkripce * MeSH
• larva genetika   MeSH
• reprodukovatelnost výsledků MeSH
• sekvenční analýza RNA MeSH
• shluková analýza MeSH
• stanovení celkové genové exprese MeSH
• transkriptom MeSH
• vývojová regulace genové exprese MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

In temperate regions, the shortening day length informs many insect species to prepare for winter by inducing diapause. The adult diapause of the linden bug, Pyrrhocoris apterus, involves a reproductive arrest accompanied by energy storage, reduction of metabolic needs, and preparation to withstand low temperatures. By contrast, nondiapause animals direct nutrient energy to muscle activity and reproduction. The photoperiod-dependent switch from diapause to reproduction is systemically transmitted throughout the organism by juvenile hormone (JH). Here, we show that, at the organ-autonomous level of the insect gut, the decision between reproduction and diapause relies on an interaction between JH signaling and circadian clock genes acting independently of the daily cycle. The JH receptor Methoprene-tolerant and the circadian proteins Clock and Cycle are all required in the gut to activate the Par domain protein 1 gene during reproduction and to simultaneously suppress a mammalian-type cryptochrome 2 gene that promotes the diapause program. A nonperiodic, organ-autonomous feedback between Par domain protein 1 and Cryptochrome 2 then orchestrates expression of downstream genes that mark the diapause vs. reproductive states of the gut. These results show that hormonal signaling through Methoprene-tolerant and circadian proteins controls gut-specific gene activity that is independent of circadian oscillations but differs between reproductive and diapausing animals.

• MeSH
• cirkadiánní hodiny fyziologie   MeSH
• fotoperioda MeSH
• Heteroptera genetika   metabolismus   MeSH
• hmyzí geny fyziologie   MeSH
• hmyzí proteiny biosyntéza   genetika   MeSH
• kryptochromy biosyntéza   genetika   MeSH
• methopren metabolismus   MeSH
• signální transdukce fyziologie   MeSH
• střevní sliznice metabolismus   MeSH
• transkripční faktory biosyntéza   genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• hmyzí proteiny MeSH
• kryptochromy MeSH
• methopren MeSH
• transkripční faktory MeSH