Epigenetic neofunctionalisation and regulatory gene evolution in grasses.

Area of Science:

• Plant genetics
• Epigenetics
• Evolutionary biology

Background:

• Genome duplication in plants leads to gene duplication and functional diversification (sub- and neofunctionalisation).
• Polycomb group (PcG) genes are crucial for development, with a single copy in Arabidopsis thaliana.
• Maize (Zea mays) possesses a pair of PcG genes, differing from its single Arabidopsis homolog.

Purpose of the Study:

• To explore the functional and evolutionary implications of duplicated PcG genes in maize.
• To investigate the unique imprinting mechanisms and parent-specific expression of maize PcG genes.
• To propose 'epigenetic neofunctionalisation' as a driver of enhanced maternal control in seed development.

Main Methods:

• Comparative genomics analysis of PcG genes in maize and Arabidopsis.
• Analysis of parental imprinting and allele-specific expression in maize endosperm.
• Review of existing literature on gene duplication, imprinting, and plant evolution.

Main Results:

• Maize PcG genes are both parentally imprinted, with maternal allele expression in the endosperm.
• Distinct imprinting mechanisms regulate the two maize PcG genes, leading to differential parent-specific expression.
• This differential imprinting suggests a novel form of functional divergence, termed 'epigenetic neofunctionalisation'.

Conclusions:

• Epigenetic neofunctionalisation of PcG genes in maize enhances maternal control over seed development.
• This mechanism may have played a role in the evolution of large and persistent endosperms in cereal grains.
• The study highlights the importance of epigenetic regulation in plant evolution following gene duplication.