Universität zu Köln

Foo, Mung Hsia ORCID: 0000-0001-7321-6572 (2025). The origin and evolution of LysM receptor-like kinases in plants. PhD thesis, Universität zu Köln.

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Abstract

The cell surface localized lysin motif (LysM) receptor-like kinases/proteins (RLKs/RLPs) function as sensors for pathogenic and symbiotic microbes in land plants, perceiving chitin, lipo-chitooligosaccharides (LCOs), and peptidoglycan. LysM-RLKs/RLPs play a crucial role in activating various responses that lead to defense against pathogens or the establishment of symbiosis. While the functions of LysM-RLKs/RLPs were well-studied in land plants, their evolutionary origin and broader functional roles remain less explored. Streptophyte algae are widely recognized as the sister lineage of land plants. Land plants are believed to have emerged from a streptophyte algal ancestor. Plant–pathogen interactions are ancient and have played a pivotal role in shaping the evolution and complexity of the plant innate immune system. Genomic analyses revealed the presence of LysM-RLKs in two streptophyte algal species, Charophyceae Chara braunii and Zygnematophyceae Spirogyra pratensis. The functional roles of LysM-RLKs in both species were subsequently characterized. Through phylogenetic analysis combined with sequence alignment, I propose that LysM-RLKs originated from the last common ancestor of Charophyceae, Zygnematophyceae, and land plants. A conserved CXC motif within the LysM ectodomains (ECDs) was identified in streptophyte algal LysM-RLKs, like those present in land plants. Structural predictions using AlphaFold2 and three-dimensional modeling revealed that the overall architecture of LysM ECD is conserved, including a chitin-binding groove within the LysM2 domain. In vitro binding assays further demonstrated the chitin-binding capability of LysM ECDs from both streptophyte algae and bryophytes, suggesting an ancestral role of LysM ECDs in chitin recognition. Intriguingly, however, chitin treatment did not trigger downstream transcriptional responses in streptophyte algae, pointing to a functional divergence in LysM-RLKs during evolution. Furthermore, genetic and interaction studies demonstrated that heterodimerization and the formation of higher-order oligomeric complexes of LysM receptors are essential for proper function in bryophytes. In contrast to bryophytes, chitin treatment did not promote homodimerization of algal LysM receptors. Overall, this study new provides an insight into the evolutionary origin and functional diversification of LysM RLKs/RLPs in plants.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Foo, Mung Hsia mhfoo89@gmail.com https://orcid.org/0000-0001-7321-6572 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-792210
Date:	2025
Language:	English
Faculty:	External institution
Divisions:	Außeruniversitäre Forschungseinrichtungen > MPI for Plant Breeding Research
Subjects:	Natural sciences and mathematics
Uncontrolled Keywords:	Keywords Language LysM UNSPECIFIED evolution UNSPECIFIED immunity UNSPECIFIED
Date of oral exam:	16 October 2025
Referee:	Name Academic Title Parker, Jane Prof. Dr. Zuccaro, Alga Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/79221