Grass awns: Morphological diversity arising from developmental constraint.

Area of Science:

• Plant Biology
• Evolutionary Developmental Biology
• Agricultural Science

Background:

• Grasses are ecologically and agriculturally dominant.
• The awned lemma aids grass seed dispersal and seedling establishment.
• Awns exhibit diverse forms and have evolved repeatedly throughout grass history.

Purpose of the Study:

• To investigate the hypothesis that conserved developmental genes underlie the evolution of awn emergence in grasses.
• To explore the relationship between awn development and leaf blade development.
• To understand how developmental conservation drives evolutionary diversity.

Main Methods:

• Comparative analysis of grass floral development.
• Hypothesizing homology between awns and leaf blades.
• Examining the role of latent developmental programs in lemma evolution.

Main Results:

• Awns are likely homologous to leaf blades, suggesting a conserved developmental pathway.
• A latent developmental program for leaf blades may be repeatedly reactivated in lemmas for awn development.
• The non-essential nature of awns allows for frequent modification and loss, driving diversity.

Conclusions:

• Deep conservation of developmental genes potentiates the evolution of diverse awn forms in grasses.
• Replicated evolution of awns demonstrates how developmental plasticity fuels biodiversity.
• Grass awns offer a model system for studying leaf development mechanisms.