CYCLOIDEA paralogs function partially redundantly to specify dorsal flower development in Mimulus lewisii

Area of Science:

• Plant evolutionary genetics
• Developmental biology
• Floral evolution

Background:

• Gene duplication is common in plants, influencing genetic programs and evolutionary novelty.
• The CYCLOIDEA (CYC)-dependent flower symmetry pathway is a key model for studying gene duplication evolution.
• A specific CYC gene lineage duplication event in higher core Lamiales (HCL) remains understudied.

Purpose of the Study:

• Investigate the evolutionary fate of duplicated HCL CYC2 genes.
• Determine the functional impact of these duplications on flower symmetry.
• Explore the regulatory interactions and retention forces of CYC paralogs in HCL.

Main Methods:

• Utilized RNA interference (RNAi) to suppress MlCYC2A and MlCYC2B expression in HCL species.
• Assessed phenotypic effects on flower symmetry in single and double gene-silenced plants.
• Conducted expression surveys of MlCYC2A, MlCYC2B, and a downstream RADIALIS (MlRAD5) ortholog.

Main Results:

• MlCYC2A and MlCYC2B jointly regulate bilateral flower symmetry.
• MlCYC2B has a distinct dorsal flower identity function and may influence carpel development.
• MlCYC2A is crucial for dorsal petal shape, and a regulatory interaction between MlCYC2A and MlCYC2B was suggested.

Conclusions:

• HCL-specific CYC paralogs are likely retained for their cooperative role in establishing bilateral flower symmetry.
• This retention mechanism mirrors that of independently evolved CYC paralogs in Antirrhinum majus (snapdragon).
• The study provides insights into the functional significance and evolutionary retention of gene duplicates in floral development.