Plasmodesmata: genetic control of cell-to-cell communication during plant defence

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Plant defence responses require the co-ordinated action of groups of cells and tissues, implicating intercellular communication as an essential component of plant defence. The pathogen-derived molecules chitin and flg22 are both capable of triggering a reduction in molecular flux between cells. A major biological question is how and why cells are isolated during early defence responses, and what contribution this makes to the deployment of a full suite of defence responses. The recent discovery that chitin-induced plasmodesmal closure is mediated by a plasmodesmata-located chitin receptor (LYM2) provides us with a handle with which to investigate this phenomenon.
The overall aim of this proposal is to determine the role of cell-to-cell communication in the context of pathogen attack and to characterise the mode of LYM2 activity within this framework. In order to achieve this, we will characterise changes to molecular flux of inert and biologically relevant molecules during pathogen attack. Thus, we will monitor the movement of fluorescent probes (inert dyes such as carboxyfluorescein diacetate) and tracers (calcium and ROS sensing dyes) during pathogen infection and exposure to pathogen derived molecules by live-cell imaging. Further, we will assess changes to a range of defence responses and pathogen susceptibility following genetic manipulation of cell-to-cell connectivity. To determine mechanistic components of the LYM2-mediated plasmodesmal closure we will use targeted and non-targeted biochemical and genetic approaches to identify protein interactors of LYM2 and downstream signalling components. Finally, we will target LysM receptor proteins and screen knockout or silenced rice lines for altered plasmodesmal flux to identify candidate chitin receptors that regulate intercellular flux in rice.
This will pioneer new avenues from which to investigate and manipulate a plant’s ability to defend itself against harmful pathogens, with ultimate application in breeding programmes and the improvement of crop plants. Accordingly, the long term objective of this research is to exploit the regulation of intercellular flux during pathogen attack to enhance plant defence in key agricultural species.

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