Evolution of the plant-microbe symbiotic 'toolkit'

Area of Science:

• Plant biology
• Mycology
• Evolutionary biology

Background:

• Arbuscular mycorrhizal fungi form crucial symbiotic associations with plants, vital for terrestrial ecosystems and sustainable agriculture.
• A core set of molecules, including proteins and microRNAs, form a symbiotic toolkit essential for establishing these plant-fungal interactions.
• This toolkit is also implicated in other plant symbiotic relationships, such as the rhizobia-legume symbiosis.

Purpose of the Study:

• To propose an evolutionary framework for the symbiotic toolkit used in plant-microbe interactions.
• To investigate the evolutionary origins and conservation patterns of genes and molecules involved in arbuscular mycorrhizal symbiosis.

Main Methods:

• Comparative genomics and phylogenetic analysis of genes involved in symbiosis across diverse plant lineages.
• Literature review and synthesis of recent findings on molecular components of plant-microbe interactions.

Main Results:

• The symbiotic toolkit exhibits varied evolutionary histories, with some components being angiosperm-specific and others highly conserved across land plants.
• Evidence suggests that certain toolkit components predate the emergence of arbuscular mycorrhizal fungi, implying pre-existing functions.
• The toolkit's ancient origins point to potential roles beyond known symbioses and hint at possible symbiotic interactions in earlier plant lineages.

Conclusions:

• The symbiotic toolkit is ancient, with components evolving at different rates and times.
• The pre-fungal existence of some toolkit elements suggests novel, undiscovered functions and evolutionary pathways.
• This framework opens avenues for exploring symbiotic associations in non-mycorrhizal plants and even in charophyte green algae.