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Open Access Research article

Effects of small Hsp genes on developmental stability and microenvironmental canalization

Kazuo H Takahashi123*, Lea Rako1, Toshiyuki Takano-Shimizu2, Ary A Hoffmann1 and Siu F Lee1

Author Affiliations

1 Centre for Environmental Stress and Adaptation Research, Department of Genetics, Bio21 Institute, The University of Melbourne, Parkville, Melbourne 3010, Australia

2 Department of Population Genetics, National Institute of Genetics, Mishima, Shizuoka-ken 411-8540, Japan

3 Research Core for Interdisciplinary Sciences, Okayama University, Tsushimanaka 3-1-1, Kita-ku, Okayama City, Japan

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BMC Evolutionary Biology 2010, 10:284  doi:10.1186/1471-2148-10-284

Published: 16 September 2010

Abstract

Background

Progression of development has to be insulated from the damaging impacts of environmental and genetic perturbations to produce highly predictable phenotypes. Molecular chaperones, such as the heat shock proteins (HSPs), are known to buffer various environmental stresses, and are deeply involved in protein homeostasis. These characteristics of HSPs imply that they might affect developmental buffering and canalization.

Results

We examined the role of nine Hsp genes using the GAL4/UAS-RNAi system on phenotypic variation of various morphological traits in Drosophila melanogaster. The stability of bristle number, wing size and wing shape was characterized through fluctuating asymmetry (FA) and the coefficient of variation (CV), or among-individual variation. Progeny of the GAL4/Hsp-RNAi crosses tended to have reduced trait means for both wing size and wing shape. Transcriptional knockdown of Hsp67Bc and Hsp22 significantly increased FA of bristle number, while knockdown of Hsp67Ba significantly increased FA and among-individual variation of wing shape but only in males. Suppression of Hsp67Bb expression significantly increased among-individual variation of bristle number. The knockdown of gene expression was confirmed for Hsp67Ba, Hsp67Bc, Hsp22, and Hsp67Bb. Correlation between FA and CV or among-individual variation of each trait is weak and not significant except for the case of male wing shape.

Conclusion

Four small Hsp genes (Hsp22, Hsp67Ba, Hsp67Bb and Hsp67Bc) showed involvement in the processes of morphogenesis and developmental stability. Due to possible different functions in terms of developmental buffering of these small Hsps, phenotypic stability of an organism is probably maintained by multiple mechanisms triggered by different environmental and genetic stresses on different traits. This novel finding may lead to a better understanding of non-Hsp90 molecular mechanisms controlling variability in morphological traits.