GSBS Student Publications

Student Author(s)

Quan Yuan

GSBS Program


Publication Date


UMMS Affiliation

Department of Neurobiology; Reppert Lab; Graduate School of Biomedical Sciences, Neuroscience Program

Document Type



Neuroscience and Neurobiology


Cryptochrome (CRY) proteins are components of the central circadian clockwork of metazoans. Phylogenetic analyses show at least 2 rounds of gene duplication at the base of the metazoan radiation, as well as several losses, gave rise to 2 cryptochrome (cry) gene families in insects, a Drosophila-like cry1 gene family and a vertebrate-like cry2 family. Previous studies have shown that insect CRY1 is photosensitive, whereas photo-insensitive CRY2 functions to potently inhibit clock-relevant CLOCK:CYCLE-mediated transcription. Here, we extended the transcriptional repressive function of insect CRY2 to 2 orders--Hymenoptera (the honeybee Apis mellifera and the bumblebee Bombus impatiens) and Coleoptera (the red flour beetle Tribolium castaneum). Importantly, the bee and beetle CRY2 proteins are not light sensitive in culture, in either degradation of protein levels or inhibitory transcriptional response, suggesting novel light input pathways into their circadian clocks as Apis and Tribolium do not have CRY1. By mapping the functional data onto a cryptochrome/6-4 photolyase gene tree, we find that the transcriptional repressive function of insect CRY2 descended from a light-sensitive photolyase-like ancestral gene, probably lacking the ability to repress CLOCK:CYCLE-mediated transcription. These data provide an evolutionary context for proposing novel circadian clock mechanisms in insects.

Rights and Permissions

Copyright 2007 The Authors. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Link to article on publisher's site

DOI of Published Version



Mol Biol Evol. 2007 Apr;24(4):948-55. Epub 2007 Jan 22.

Journal/Book/Conference Title

Molecular biology and evolution

Related Resources

Link to Article in PubMed

PubMed ID