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First published online 2 January 2008
doi: 10.1242/dev.015263

Development 135, 569-577 (2008)
Published by The Company of Biologists 2008
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The role of Broad in the development of Tribolium castaneum: implications for the evolution of the holometabolous insect pupa

Yuichiro Suzuki, James W. Truman* and Lynn M. Riddiford*,{dagger}

Department of Biology, University of Washington, Box 351800, Seattle, WA 98195-1800, USA.

{dagger} Author for correspondence (e-mail: riddifordl{at}janelia.hhmi.org)

Accepted 6 November 2007

The evolution of complete metamorphosis in insects is a key innovation that has led to the successful diversification of holometabolous insects, yet the origin of the pupa remains an enigma. Here, we analyzed the expression of the pupal specifier gene broad (br), and the effect on br of isoform-specific, double-stranded RNA-mediated silencing, in a basal holometabolous insect, the beetle Tribolium castaneum. All five isoforms are weakly expressed during the penultimate instar and highly expressed during the prepupal period of the final instar. Application of hydroprene, a juvenile hormone analog, during the penultimate instar caused a repeat of the penultimate br expression patterns, and the formation of supernumerary larvae. Use of dsRNA against the br core region, or against a pair of either the br-Z2 or br-Z3 isoform with the br-Z1 or br-Z4 isoform, produced mobile animals with well-differentiated adult-like appendages, but which retained larval-like urogomphi and epidermis. Disruption of either the br-Z2 or the br-Z3 isoform caused the formation of shorter wings. Disruption of both br-Z1 and br-Z4 caused the appearance of pupal traits in the adults, but disruption of br-Z5 had no morphological effect. Our findings show that the br isoform functions are broadly conserved within the Holometabola and suggest that evolution of br isoform expression may have played an important role in the evolution of the pupa in holometabolous insects.

Key words: Metamorphosis, Broad, Juvenile hormone, Pupation, Tribolium




This article has been cited by other articles:


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B. Konopova and M. Jindra
Broad-Complex acts downstream of Met in juvenile hormone signaling to coordinate primitive holometabolan metamorphosis
Development, February 1, 2008; 135(3): 559 - 568.
[Abstract] [Full Text] [PDF]


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