Smoke signals and seed dormancy: where next for MAX2?

Area of Science:

• Plant Biology
• Molecular Plant Science
• Evolutionary Biology

Background:

• The F-box protein MAX2 in Arabidopsis thaliana plays a role in leaf senescence, seedling development, and seed germination.
• MAX2 mediates responses to both strigolactones and karrikins, structurally related signaling molecules.
• The precise mechanisms of MAX2's dual signaling roles and its evolutionary origins are not fully understood.

Purpose of the Study:

• To investigate the evolutionary history and functional divergence of MAX2 in response to strigolactones and karrikins.
• To explore how MAX2 mediates distinct plant responses to these signaling molecules across different plant lineages.

Main Methods:

• Comparative analysis of MAX2 orthologs across land plants, including mosses and parasitic Orobanchaceae.
• Phylogenetic analysis to identify distinct MAX2 sub-clades.

Main Results:

• MAX2 orthologs are conserved across land plants, suggesting an ancient origin for strigolactone and karrikin signaling.
• Orobanchaceae MAX2 orthologs form a distinct evolutionary clade, correlating with their specialized strigolactone-dependent germination.
• Evidence suggests lineage-specific evolution of MAX2 has led to specialized responses to these signaling molecules.

Conclusions:

• The MAX2-mediated signaling pathway for strigolactones and karrikins has ancient origins in land plants.
• Evolutionary divergence of MAX2 has shaped specialized responses to these plant hormones in different lineages, particularly in parasitic plants.