Coupled enhancer and coding sequence evolution of a homeobox gene shaped leaf diversity

Area of Science:

• Evolutionary developmental biology
• Plant morphology
• Molecular evolution

Background:

• Understanding the genetic mechanisms driving the diversification of biological forms is a key challenge in evolutionary biology.
• Leaf shape in crucifers provides a tractable system for studying morphological evolution.

Purpose of the Study:

• To investigate the molecular mechanisms underlying the evolution of crucifer leaf shape.
• To identify the roles of regulatory and coding sequence changes in the REDUCED COMPLEXITY (RCO) gene.

Main Methods:

• Comparative genomics to identify regulatory and coding variants in RCO.
• Gene expression analysis to assess changes in RCO activity.
• Functional assays to evaluate the impact of RCO variants on leaf morphology and protein stability.
• Phylogenetic analysis to detect positive selection.

Main Results:

• Evolution of an enhancer element in RCO altered gene expression patterns, affecting leaf shape.
• A concurrent amino acid substitution reduced RCO protein stability, mitigating pleiotropic effects.
• Evidence of positive selection was found in both regulatory and coding sequences of RCO.
• Modulating RCO activity improved plant physiological performance.

Conclusions:

• The interplay between enhancer and coding sequence evolution in RCO provided an adaptive pathway for morphological evolution.
• RCO gene evolution offers insights into how novel forms arise and become established.
• This study highlights the importance of regulatory changes in driving evolutionary innovation.