Evolution of the land plant exocyst complexes

Area of Science:

• Plant cell biology
• Molecular evolution
• Protein complex evolution

Background:

• The exocyst complex is crucial for exocytosis and cell growth in eukaryotes.
• Plant homologs of exocyst subunits are known to form complexes and aid in polarized growth.
• The evolutionary history and diversity of plant exocyst complexes remain largely unexplored.

Purpose of the Study:

• To conduct a phylogenetic analysis of land plant exocyst subunits.
• To investigate the evolutionary trajectories and diversification patterns of exocyst genes in plants.
• To understand the implications of exocyst diversity for plant cell structure and function.

Main Methods:

• Phylogenetic analysis of exocyst subunit genes from sequenced plant genomes.
• Comparative genomics to trace the evolution and duplication events of exocyst genes.
• Analysis of gene family expansion, particularly for Exo70 and Exo84 subunits.

Main Results:

• Core exocyst subunits (Sec3, Sec5, Sec6, Sec8, Sec10) show limited duplication in tracheophytes.
• Peripheral subunits, especially Exo70 and Exo84, exhibit significant gene family expansion in land plants.
• Evidence suggests three ancestral Exo70 paralogs diversified extensively throughout land plant evolution.
• Plant exocyst subunit diversity is unparalleled compared to other studied organisms.

Conclusions:

• Land plants possess a remarkable diversity of exocyst variants, not a single conserved complex.
• The extensive diversification of exocyst subunits, particularly Exo70, likely underpins the complex structural requirements of multicellular plants.
• This diversity may be linked to the maintenance of intricate endomembrane and cell surface structures in plants.