Evolution in action: following function in duplicated floral homeotic genes

Area of Science:

• Evolutionary biology
• Developmental genetics
• Plant biology

Background:

• Gene duplication is a key evolutionary mechanism, enabling the emergence of new gene functions through processes like subfunctionalization and neofunctionalization.
• The MADS-box genes AGAMOUS (Arabidopsis) and PLENA (Antirrhinum) are crucial C-function genes for reproductive organ development.
• These genes are functionally similar, encoding related homeotic transcription factors, but their evolutionary relationship is complex.

Purpose of the Study:

• To investigate the evolutionary trajectory of duplicated genes, specifically focusing on the C-function MADS-box genes PLENA and AGAMOUS.
• To confirm the nonorthologous nature of PLENA and AGAMOUS and their origins from a common ancestor's duplication event.
• To illustrate how subfunctionalization and neofunctionalization drive functional divergence in duplicated genes, impacting morphology.

Main Methods:

• Phylogenetic analyses were employed to determine the evolutionary relationships between PLENA and AGAMOUS.
• Genome synteny was used to confirm the gene duplication event in a common ancestor.
• Functional studies in transgenic Antirrhinum and Arabidopsis were conducted to observe the morphological consequences of gene functional divergence.

Main Results:

• Phylogenetic and synteny analyses confirmed that PLENA and AGAMOUS are nonorthologous genes originating from a duplication event in a shared ancestor.
• Independent subfunctionalization occurred in the orthologs SHATTERPROOF (Arabidopsis) and FARINELLI (Antirrhinum), involving regulatory and protein function changes.
• The functional divergence between PLENA and FARINELLI resulted in observable morphological differences in both Antirrhinum and Arabidopsis, demonstrating subfunctionalization at the protein level.

Conclusions:

• The study provides a clear example of how gene duplication can lead to divergent evolutionary paths for gene functions, highlighting the role of chance.
• Subfunctionalization of duplicated genes, as seen in PLENA and FARINELLI, can lead to distinct roles in development, such as differential promotion of male or female reproductive development.
• The findings underscore the importance of gene duplication as a source of evolutionary innovation and the unpredictable nature of functional divergence.