Anciently duplicated <Emphasis Type="Italic">Broad Complex</Emphasis> exons have distinct temporal functions during tissue morphogenesis |
| |
Authors: | Rebecca F Spokony Linda L Restifo |
| |
Institution: | (1) Graduate Interdisciplinary Program in Insect Science, University of Arizona, Tucson, AZ 85721-0108, USA;(2) ARL Division of Neurobiology, University of Arizona, Tucson, AZ 85721-0077, USA;(3) Department of Neurology, Arizona Health Sciences Center, Tucson, AZ 85724, USA;(4) Present address: Department of Human Genetics, The University of Chicago, 920 E 58th St, Chicago, IL 60637, USA |
| |
Abstract: | Broad Complex (BRC) is an essential ecdysone-pathway gene required for entry into and progression through metamorphosis in Drosophila melanogaster. Mutations of three BRC complementation groups cause numerous phenotypes, including a common suite of morphogenesis defects involving central nervous
system (CNS), adult salivary glands (aSG), and male genitalia. These defects are phenocopied by the juvenile hormone mimic
methoprene. Four BRC isoforms are produced by alternative splicing of a protein-binding BTB/POZ-encoding exon (BTB
BRC
) to one of four tandemly duplicated, DNA-binding zinc-finger-encoding exons (Z1
BRC
, Z2
BRC
, Z3
BRC
, Z4
BRC
). Highly conserved orthologs of BTB
BRC
and all four Z
BRC
were found among published cDNA sequences or genome databases from Diptera, Lepidoptera, Hymenoptera, and Coleoptera, indicating
that BRC arose and underwent internal exon duplication before the split of holometabolous orders. Tramtrack subfamily members, abrupt, tramtrack, fruitless, longitudinals lacking (lola), and CG31666 were characterized throughout Holometabola and used to root phylogenetic analyses of Z
BRC
exons, which revealed that the Z
BRC
clade includes Z
abrupt
. All four Z
BRC
domains, including Z4
BRC
, which has no known essential function, are evolving in a manner consistent with selective constraint. We used transgenic
rescue to explore how different BRC isoforms contribute to shared tissue-morphogenesis functions. As predicted from earlier
studies, the common CNS and aSG phenotypes were rescued by BRC-Z1 in rbp mutants, BRC-Z2 in br mutants, and BRC-Z3 in 2Bc mutants. However, the isoforms are required at two different developmental stages, with BRC-Z2 and -Z3 required earlier than
BRC-Z1. The sequential action of BRC isoforms indicates subfunctionalization of duplicated Z
BRC
exons even when they contribute to common developmental processes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
| |
Keywords: | Insect Crustacean Exon duplication Phylogenetic tree Molting hormone Purifying selection |
本文献已被 PubMed SpringerLink 等数据库收录! |
|