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Non-optimal codon usage is a mechanism to achieve circadian clock conditionality
Yao Xu1, Peijun Ma, Premal Shah
1Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA.
Nature
|February 19, 2013
Summary
Cyanobacteria use non-optimal gene codons to control circadian rhythms, adapting to environmental changes. This natural selection against optimal codons optimizes fitness by modulating circadian amplitude, challenging previous assumptions about codon usage.
Area of Science:
- Molecular Biology
- Chronobiology
- Evolutionary Biology
Background:
- Circadian rhythms are biological oscillations crucial for adapting to daily environmental cycles.
- In cyanobacteria, the KaiABC proteins form the core circadian clock oscillator.
- Optimal codon usage typically enhances translational efficiency for essential genes, but kaiBC genes show bias.
Purpose of the Study:
- To investigate the molecular basis of circadian rhythm conditionality in Synechococcus elongatus.
- To determine the role of non-optimal codon usage in regulating circadian gene expression.
- To explore the adaptive significance of codon usage bias in response to environmental conditions.
Main Methods:
- Experimental optimization of the kaiBC gene sequence to enhance KaiB and KaiC protein expression.
- Assessment of intrinsic circadian rhythmicity at different temperatures.
- Measurement of cellular fitness under varying temperature and circadian rhythm conditions.
Main Results:
- Optimizing kaiBC codon usage enhanced intrinsic rhythmicity at cool temperatures.
- Cellular fitness was highest when circadian rhythms were suppressed at cool temperatures.
- Natural selection favors suppression of robust circadian systems in cooler environments.
Conclusions:
- Non-optimal codon usage in kaiBC genes acts as a post-transcriptional mechanism to regulate circadian rhythm amplitude.
- This codon-based regulation allows adaptive switching between circadian and non-circadian states in response to environmental cues.
- The study demonstrates natural selection against optimal codons for adaptive phenotypic variation and organismal fitness.
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