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.
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Claims 10
Claim · model-written summary
LysM-RLKs are present in the charophyte alga Chara braunii.
- Taxon
- Chara braunii
Chara brauniie0 - Outcome
- presence of LysM-RLKse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Genomic analyses revealed the presence of LysM-RLKs in two streptophyte algal species, Charophyceae Chara braunii and Zygnematophyceae Spirogyra pratensis”
Claim · model-written summary
LysM-RLKs are present in the zygnematophyte alga Spirogyra pratensis.
- Taxon
- Spirogyra pratensisSpirogyra pratensise0
- Outcome
- presence of LysM-RLKse0
Verbatim
e0“Genomic analyses revealed the presence of LysM-RLKs in two streptophyte algal species, Charophyceae Chara braunii and Zygnematophyceae Spirogyra pratensis”
Claim · model-written summary
LysM-RLKs originated from the last common ancestor of Charophyceae, Zygnematophyceae and land plants.
- Taxon
- land plantsEmbryophytae1
- Outcome
- originated from the last common ancestore1
Verbatim
e1“I propose that LysM-RLKs originated from the last common ancestor of Charophyceae, Zygnematophyceae, and land plants”
Claim · model-written summary
A conserved CXC motif within the LysM ectodomains is present in streptophyte algal LysM-RLKs.
Verbatim
e2“A conserved CXC motif within the LysM ectodomains (ECDs) was identified in streptophyte algal LysM-RLKs”
e3“Streptophyte algae are widely recognized as the sister lineage of land plants”
Claim · model-written summary
Structural predictions indicate that the overall LysM ectodomain architecture is conserved, including a chitin-binding groove in the LysM2 domain.
- Taxon
- land plantsEmbryophytae5
- Outcome
- overall architecture of LysM ECDe4
- Qualifier
- chitin-binding groove within the LysM2 domaine4
Verbatim
e4“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”
e5“like those present in land plants”
Claim · model-written summary
LysM ectodomains from streptophyte algae bind chitin in vitro.
Verbatim
e6“In vitro binding assays further demonstrated the chitin-binding capability of LysM ECDs from both streptophyte algae and bryophytes”
Claim · model-written summary
LysM ectodomains from bryophytes bind chitin in vitro.
Verbatim
e6“In vitro binding assays further demonstrated the chitin-binding capability of LysM ECDs from both streptophyte algae and bryophytes”
Claim · model-written summary
Chitin treatment did not trigger downstream transcriptional responses in streptophyte algae.
- Taxon
- streptophyte algaee7
- Treatment
- chitin treatmente7
- Outcome
- downstream transcriptional responsese7
- Direction
- did not triggere7
Not reportedComparator
Verbatim
e7“chitin treatment did not trigger downstream transcriptional responses in streptophyte algae”
Claim · model-written summary
Heterodimerization and higher-order oligomeric complexes of LysM receptors are essential for proper function in bryophytes.
Verbatim
e0“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”
Claim · model-written summary
Chitin treatment did not promote homodimerization of algal LysM receptors, unlike in bryophytes.
Verbatim
e1“Streptophyte algae are widely recognized as the sister lineage of land plants”
e2“In contrast to bryophytes, chitin treatment did not promote homodimerization of algal LysM receptors”