Award details

Plasmodesmata as regulators of the growth-defence trade-off

Reference	BB/X007685/1
Principal Investigator / Supervisor	Dr Christine Faulkner
Co-Investigators / Co-Supervisors
Institution	John Innes Centre
Department	Cell and Develop Biology
Funding type	Research
Value (£)	549,882
Status	Current
Type	Research Grant
Start date	01/04/2023
End date	31/03/2026
Duration	36 months

Abstract

Plant cells are cytoplasmically connected to their neighbours via plasma membrane-lined tunnels called plasmodesmata. Plasmodesmata allow the passage of molecules between cells and whether they are closed or open regulates the exchange of information and resources between cells and tissues. The plasma membrane that lines plasmodesmata is distinct in composition and function from the rest of the plasma membrane, suggesting independent control of cell-to-cell connectivity. One context for this is immune responses and our recent findings show that plasmodesmal responses are differently executed in mature and young leaves: young leaves do not close their plasmodesmata in response to microbial molecules like is observed in mature tissues, suggesting that young tissues might prioritise connection to the carbon source over defence. This proposal aims to exploit this finding to address how plasmodesmata regulate the the growth-defence trade-off. We will profile plasmodesmal responses across a range of tissue ages and physiological states and manipulate the sink-source status of tissues to reprogramme plasmodesmal responses. Plasmodesmal closure regulates the amplitude and timing of transcriptional responses to microbial molecules, and we will leverage this and other immune responses to determine how plasmodesmal closure influences immune responses in sink tissues. We will use mutants for altered plasmodesmal responses, as well as genetic tools to manipulate plasmodesmal closure, to assay for immune outputs. We will also use live-imaging and proteomics to determine how the composition of responsive and non-responsive plasmodesmata differs, and volume electron microscopy and super-resolution light microscopy methods to assess their structural differences. Thus, we will define the contexts in which plasmodesmata respond to immune signals and determine how plasmodesmata regulate the growth-defence trade-off.

Summary

Plant cells are connected to their neighbours for communication and resource exchange, with this interconnectivity enabling co-ordinated growth and responses across multicellular tissues and organs. Cell-to-cell connectivity is enabled by plasmodesmata, plasma membrane-lined 'tunnels' that connect neighbouring cells across the cell wall and establish both plasma membrane and cytoplasmic continuity between neighbouring cells. Plasmodesmata effectively act as 'sluice gates' to regulate the flux of soluble molecules, closing and opening in response to a range of stimuli. The plasma membrane that lines plasmodesmata is functionally distinct from the rest of the membrane, allowing discrete and independent functional control of their responses. Plasmodesmata respond to many stress signals by initiating a signalling cascade that results in their closure, and this was observed to be critical for optimal immune signalling when cells perceive microbe threats. In addition to contributing to immune responses, plasmodesmal closure induces cellular isolation that must limit the exchange of resources such as carbon, and signals relevant to other cellular processes. Indeed, plasmodesmata act as a key passage through which sugar is distributed through a plant, raising the possibility that plasmodesmal closure carries significant consequences for carbon allocation in a context in which sugars are required to maintain growth. We recently discovered that by contrast with mature leaves, young leaves do not close their plasmodesmata in response to microbe perception. This supports the hypothesis that young tissues prioritise growth over defence, keeping plasmodesmata open to maintain the flow of sugar from source tissues to sustain growth processes. This, and the observation that plasmodesmal responses are independently regulated, suggests plasmodesmata are a central component of the mechanism by which the trade-off between growth and defence is balanced. The proposal will test this model, determining whether plasmodesmal closure is differently regulated across a range of developmental stages, physiological states and stress contexts. We will exploit our knowledge that plasmodesmata regulate the amplitude and timing of immune responses, to profile how plasmodesmal manipulation perturbs the growth-defence trade-off in sink tissues. How plasmodesmata can differentially respond must depend on the machinery present to execute a response and therefore we will characterise the different protein composition of plasmodesmata in tissues that do and do not close their plasmodesmata. Further, as the structure of plasmodesmata has been shown to have some correlation with the sink or source status, we will profile plasmodesmal structure to identify what features define plasmodesmal responsiveness. Thus, we will define the mechanistic elements required for a plasmodesma to respond to stress. This proposal will detail how plasmodesmata regulate carbon allocation in an immune signalling context and how they function as a component of the signalling hub that controls the growth-defence trade-off. Beyond immune responses, regulation of carbon allocation is relevant to a range of physiological contexts and this proposal will therefore establish general understanding of how carbon resources are partitioned and consumed, finding application across plant growth, development and environmental responses.

Committee	Research Committee B (Plants, microbes, food & sustainability)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

I accept the terms and conditions of use (opens in new window)

export PDF file

back to list new search