Regulation of plasmodesmal receptor sorting and signalling by membrane scaffolds – the role of tetraspanins and flotillins

Samwald, Sebastian (2022) Regulation of plasmodesmal receptor sorting and signalling by membrane scaffolds – the role of tetraspanins and flotillins. Doctoral thesis, University of East Anglia.

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Plants can perceive and respond to the presence of microorganisms such as fungi and bacteria in their environment. One way for plants to perceive the presence of fungi is to detect the fungal cell wall component chitin, via pattern recognition receptors (PRR). During the perception of pathogens, plant cells close the membrane lined channels connecting the cytoplasm of adjacent cells (plasmodesmata) by depositing callose in the cell wall, and thereby restrict the molecular flux between neighbouring cells. Three different PRR are necessary for chitin-triggered plasmodesmal closure in Arabidopsis: LYSM DOMAIN GPIANCHORED PROTEIN 2 (LYM2), LYSM-CONTAINING RECEPTOR-LIKE KINASE 4 (LYK4), and LYSM-CONTAINING RECEPTOR-LIKE KINASE 5 (LYK5). Out of those three, only LYM2 is enriched at plasmodesmata, and chitin triggers a further increase of this enrichment. However, the molecular mechanisms underlying this process remain to be elucidated.

In this thesis I explore prerequisites and characteristics necessary to achieve this plasmodesmal localisation. I further show that all three receptors LYM2, LYK4 and LYK5 associate with each other in planta, and investigate how LYK5 could be important for chitintriggered plasmodesmal closure, even though it is absent at plasmodesmata itself.

I further demonstrate that not only receptors but also proteins of two different scaffolding families — the tetraspanins and flotillins — are necessary for these responses. Both of these families are known for their presence and orchestration of specialised membrane domains such as nanodomains. My data reveal that they are also important for signalling responses at the specialised plasmodesmal PM microdomain. I show how both tetraspanins and flotillins are necessary to achieve chitin-triggered ROS bursts, plasmodesmal regulation, as well as plant resistance against pathogenic fungi comparable to wild-type plants.

Together, the data presented in this work generate new insights on how chitin-triggered signalling processes depend on different receptors, and also on their partner scaffolding proteins, thereby creating new hypotheses and opportunities for future investigations.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 16 Feb 2023 13:25
Last Modified: 16 Feb 2023 13:25

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