Lipochitooligosaccharide recognition: an ancient story.

Area of Science:

• Plant science
• Molecular biology
• Evolutionary biology

Background:

• Chitin, a natural polysaccharide, and its derivatives have significant interactions with plants.
• Chitooligosaccharides induce plant innate immunity, while modified forms (LCOs) act as signaling molecules in plant symbioses.

Purpose of the Study:

• To review the evolutionary origins of symbiotic lipochitooligosaccharide (LCO) recognition in plants.
• To explore the relationship between LCO perception, plant innate immunity, and symbiotic signaling.

Main Methods:

• Literature review of studies on chitin, chitooligosaccharides, and LCOs in plant-microbe interactions.
• Analysis of proposed evolutionary pathways for symbiotic signaling molecule perception.
• Synthesis of evidence linking LCO recognition to plant innate immunity and symbiosis.

Main Results:

• Unmodified chitooligosaccharides (degree of polymerization 6–8) are potent inducers of plant innate immunity.
• Acylated chitooligosaccharides (LCOs) function as Nod factors in legume-rhizobium symbiosis and Myc factors in arbuscular mycorrhizal (AM) symbiosis.
• Evidence suggests LCO perception in symbiosis may have evolved from plant innate immunity signaling, potentially predating Nod factor evolution.

Conclusions:

• Lipochitooligosaccharide (LCO) recognition in symbiotic contexts likely evolved from pre-existing plant innate immunity signaling pathways.
• Understanding the evolutionary history of LCO recognition provides insights into the development of plant-microbe symbioses.
• The study highlights the complex evolutionary interplay between plant immunity and symbiotic signaling molecules.