Physcomitrella MADS-box genes regulate water supply and sperm movement for fertilization

Area of Science:

• Plant developmental biology
• Evolutionary genetics
• Molecular genetics

Background:

• MIKC^C-type MADS-box genes are crucial transcription factors in flowering plant development, particularly floral organ identity.
• Their evolutionary history and precise functions in non-flowering plants remain largely unknown.
• Understanding these genes in basal land plants can illuminate their diversification and functional evolution.

Purpose of the Study:

• To investigate the functions of MIKC^C-type MADS-box genes in the moss Physcomitrella patens.
• To elucidate the roles of these genes in enabling fertilization and their evolutionary trajectory.
• To understand the ancestral functions of MADS-box genes in land plant diversification.

Main Methods:

• Phylogenetic analysis of MIKC^C-type MADS-box genes across land plants.
• Analysis of protein localization in Physcomitrella patens.
• Creation and analysis of deletion mutants and overexpression lines for all six P. patens MIKC^C-type MADS-box genes.

Main Results:

• Three MIKC^C-type MADS-box genes in P. patens redundantly regulate stem cell division and growth for water conduction.
• These genes also play a role in the formation of sperm with motile flagella.
• The water conduction function is conserved in flowering plants, while the sperm formation role was lost with the loss of sperm.

Conclusions:

• MIKC^C-type MADS-box genes in mosses have essential roles in fertilization, impacting both vegetative development for water transport and gamete formation.
• Functional divergence of these genes occurred during land plant evolution, with some roles retained and others lost.
• This study provides insights into the ancestral functions of MADS-box genes and their contribution to plant reproductive strategies.