Plants are under constant stress from attackers as well as abiotic factors, which threaten their survival and that of their offspring. However, being well protected though the use of defence mechanisms is not always the best strategy for countering environmental threats due to trade-offs associated with such responses. Hence, plants have developed a number of systems for monitoring changes in their growth and structure and initiating a specific response. One of these mechanisms, known as cell wall integrity (CWI, or WALLIN), is based on the cell wall, an extremely dynamic and complex structure that is essential to the protection of plant cells against external threats. It also helps to regulate plant growth and development. Studies have shown the existence of a CWI maintenance mechanism that integrates many different sources of signalling into one overarching signalling system. The EU-funded project SIGNWALLING (Plant immunity regulated by cell wall integrity) explored some of the CWI-mediated mechanisms of plant resistance against pathogens and revealed some of its molecular basis. Researchers monitored cell wall modifications from 30 Arabidopsis thaliana mutants using Fourier transform infrared spectroscopy to recognise polymers and functional groups and to provide information about their organisation. Generated data was modelled, revealing the importance of a handful of cell wall epitopes in regulating plant resistance phenotypes. Two cell wall mutants were selected according to the predictive model and the molecular basis of the wall mediated-resistance found within them was characterised. In addition, several chemically extracted wall fractions were further chromatographically purified and tested for their ability to activate pattern triggered immunity. The immune active components were shown to be carbohydrate in nature. Therefore, monosaccharide and glycosidic linkage analyses were conducted to determine the structure of these active endogenous molecules known as damage-associated molecular patterns (DAMPS). SIGNWALLING will further investigate the novel carbohydrate DAMP structures to determine their ability to protect crops against pathogens. The efforts promise to open up novel research avenues based on the potential to remodel the plant cell wall.
Cell walls, plant immunity, cell wall integrity, SIGNWALLING, plant resistance