Universität zu Köln

Yan, Yijia ORCID: 0009-0002-4742-4073 (2024). Deciphering the role of the malectin-like RLK and LRR-RLKs in the liverwort Marchantia polymorpha. PhD thesis, Universität zu Köln.

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Abstract

FERONIA (FER) is a member of the malectin-like receptor-like kinase (MLR) family that plays versatile roles in various plant processes such as reproduction, cell growth, and immunity in angiosperms. FER perceives RAPID ALKALINISATION FACTOR (RALF) peptides to modulate development and immunity. While MLRs are conserved among land plants, the molecular and biological functions of FER in non-flowering plants remain largely unexplored. The liverwort Marchantia polymorpha encodes a single homologue of FER, known as MpFER, which has been reported to play roles in growth and development. However, its ligands and role in immunity have not yet been described. In this study, I found that M. polymorpha recognises and responds to MpRALF1 and MpRALF3 peptides by producing reactive oxygen species (ROS) in an MpFER-dependent manner. The rhizoids and rhizoid-initiated areas mainly contributed significantly to ROS production, indicating that MpRALFs and MpFER function as a module in M. polymorpha. Using the proximity labelling-based interactome analysis, LysM RECEPTOR-LIKE KINASE1, MpLYK1, and LysM RECEPTOR-LIKE KINASE-RELATED, MpLYR, were identified as candidate interactors of MpFER, pointing to a potential crosstalk between MpFER- and MpLYK1-mediated signalling pathways. Transcriptome analysis of M. polymorpha treated with MpRALF1 suggested that MpRALF1 positively regulates defence responses. This was supported by the finding that MpRALF1 treatment primed the resistance of M. polymorpha against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 (Pto DC3000). Altogether, this study demonstrates the conservation of the RALF‒FER module and its contribution to plant immunity in the liverwort M. polymorpha. The leucine-rich repeat receptor-like kinases (LRR-RLKs) family is the most prominent and best-characterised RLK family in plants. LRR-RLKs are structurally classified into 14 subfamilies. Several subfamily XII LRR-RLKs have been proven to function as pattern-recognition receptors (PRRs) that sense pathogen invasions. Subfamily II LRR-RLKs are generally considered to function as co-receptors, required for LRR-RLK-type PRR-mediated signalling. Within subfamily II, SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASES3 (SERK3) was identified as a co-receptor for the PRRs, and thereby plays a role in immunity in the angiosperm Arabidopsis thaliana. AtSERK3 also functions with other LRR-RLKs, including BRASSINOSTEROID INSENSITIVE1 (BRI1), to regulate growth and development. The conserved tyrosine residue in AtSERK3 is crucial for signalling specificity in differentiating PRR- and BRI1-mediated pathways. Marchantia polymorpha encodes three subfamily II LRR-RLKs, MpSERK, MpAPEX, and MpCIK, whose functions are poorly characterised. Here, I investigated the functions of MpSERK and MpAPEX. I found that MpAPEX has a minimal role in growth and development. Mpapex mutants tended to be resistant against Pto DC3000 compared to wild-type plants, indicating a possible role for MpAPEX in immunity. In contrast, I found that MpSERK plays a crucial role in growth and sexual or vegetative reproduction. Complementation analysis demonstrated that the conserved tyrosine residue of MpSERK is important for thallus growth. Proximity labelling-based interactome analysis identified MpBIR as an MpSERK interactor. Mpbir mutants displayed defects in reproductive organ development. Transcriptome analysis revealed that the patterns of development- and immunity-related gene expression in Mpserk and Mpbir were antagonistic, suggesting that MpBIR functions as an MpSERK repressor. I further found that Pto DC3000 barely grew on Mpbir, highlighting the significant role of the MpSERK‒MpBIR module in immunity. Taken together, this study shows that MpAPEX and MpSERK play roles in immunity. The SERK‒BIR working module appears to regulate immunity and development across land plants.

Item Type:	Thesis (PhD thesis)
Translated title:	Title Language UNSPECIFIED English
Creators:	Creators Email ORCID ORCID Put Code Yan, Yijia yj.yan@outlook.com orcid.org/0009-0002-4742-4073 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-747244
Date:	19 December 2024
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Außeruniversitäre Forschungseinrichtungen > MPI for Plant Breeding Research
Subjects:	Natural sciences and mathematics
Uncontrolled Keywords:	Keywords Language plant immunity UNSPECIFIED PTI UNSPECIFIED Marchantia polymorpha UNSPECIFIED
Date of oral exam:	21 November 2024
Referee:	Name Academic Title Zuccaro, Alga Prof. Dr. Parker, Jane Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/74724