Introduction and aims

Cell walls provide plant cells with structural support during growth and differentiation as well as with protection against environmental stress. However, they are not simply static exoskeletons, but highly dynamic and adaptive in their structure and composition dependent on the requirements they have to fulfil during development and response to biotic or abiotic stress. Adaptation to the environment is controlled by a dedicated mechanism to maintain functional cell wall integrity (CWI). The available evidence suggests that the CWI mechanism is an important regulator of cell wall and carbohydrate metabolism and that signalling of sugar levels is essential for its function. Both cell wall and carbohydrate metabolism are strongly affecting pathogen defense, suggesting significant co-regulation with the CWI mechanism.

By performing a forward genetic screen I will identify novel components involved in sugar-signalling in the context of CWI maintenance and pathogen defence. Using a combination of genetic mapping and next-generation sequencing, I will determine the identity of the components, whose specific activities will be identified through targeted functional analyses. In the second part of my project I will determine the functions of the signaling metabolites trehalose-6-phosphate (T6P) and glycerol-3-phophate (G3P) in CWI maintenance and analyse the osmo-sensitive regulation of these functions. This will include analysis of developmental, hormonal and structural responses to CWI impairment in overexpression and knockout lines of candidate genes already identified. To further characterize the mode of action of identified osmo-sensitive processes, I will quantify metabolite levels and enzyme activities related to T6P and G3P metabolism.

This project will make use of the circumstance that CWI maintenance is involved in a variety of biological processes to identify signalling components and osmo-sensitive mechanisms for the coordination of carbohydrate metabolism with cell wall metabolism and pathogen defence. The knowledge generated in this project will provide novel functional insights into the metabolic processes relevant for facilitating bioenergy production and increasing the yield of food crops.

 

Overview of selected activities and outputs

In September 2016 Timo Engelsdorf organised the participation of the research group in NTNU´s researchers night. This is an event where appropriate. 1500 high school pupils visit research laboratories on the Gløshaugen campus of the university to explore what it means to do research in natural sciences.

 

Scientific outputs

One of the work streams aimed to understand how the cell wall integrity maintenance mechanism and plant immunity interact in order to adapt responses of the plant to a changing environment. This involves modulating responses to ensure that they are successfully helping the plant to adapt to both biotic and abiotic stress. There results of this work are provisionally accepted for publication in Science Signalling. The main findings have already been made available to the public in open access format via BioRxiv. The figure shown below illustrates the mode of interaction between cell wall integrity maintenance and immune signalling.

Cell wall integrity (CWI) signaling and pattern-triggered immunity (PTI) regulate jointly plant defense responses. Cell wall damage arising during biotic and abiotic stress induces both THE1-mediated CWI signaling and AtPROPEP1 / AtPROPEP3-mediated PTI signaling. CWI signaling involves MCA1, FEI2 and other components (not shown), which activate stress responses including production of phytohormones like Jasmonic acid and  Salicylic acid  as well as cell wall components like lignin. If CWD persists and other pathogen-derived stimuli are detected simultaneously, PTI-controlled defense responses are enhanced via AtPEP1 and AtPEP3 and CWI-controlled ones are inhibited.