Abstract
BackgroundProgression 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.ResultsWe 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.ConclusionFour 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.
Highlights
Progression of development has to be insulated from the damaging impacts of environmental and genetic perturbations to produce highly predictable phenotypes
Based on the mixed results, Debat et al [7] suggested that Hsp90 is one of the multiple factors that participate in the developmental buffering of morphological traits rather than the only controlling factor
Repeatability and measurement error Repeatability of the acquisition of the individual landmark coordinates and CS was very high (R > 0.997 and 0.982 respectively), Procrustes ANOVA indicated that the contribution of measurement error to overall shape variation was small (Table 2), and the effect of fluctuating asymmetry (FA) was highly significant in all cases
Summary
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. Waddington [1] suggested a conceptual mechanism called canalization that buffers developmental processes from environmental and genetic perturbations and helps to produce constant phenotypes Molecular chaperones, such as the heat shock proteins (HSPs), are known to buffer various environmental stresses, and are deeply involved in protein homeostasis [2]. Inhibition of Hsp, one of the molecular chaperones, has been found to increase phenotypic diversity in various organisms such as Drosophila, Arabidopsis, and zebrafish [3,4,5] It suggests that Hsp buffers developmental perturbations on morphological traits in these species. Based on the mixed results, Debat et al [7] suggested that Hsp is one of the multiple factors that participate in the developmental buffering of morphological traits rather than the only controlling factor
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