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Disease and immunity in marine brown algae

Final Report Summary - DIMBA (Disease and immunity in marine brown algae)

Project context and objectives

Do algae ever get sick, and why does it matter?

Brown algae make up over 70% of the biomass of our rocky seashores. As the seaweed aquaculture industry grows exponentially worldwide, their economic importance is increasing rapidly. In the United Kingdom and other Western countries, algae are being considered as a potential sustainable biofuel source. The development of experimental aquaculture facilities is currently attracting considerable investment in the context of the ongoing transition towards a low carbon economy.

Like any other living organism, brown algae are plagued by diseases caused by fungi, bacteria or viruses. Among them, Eurychasma dicksonii - the parasite that I am studying - is very common and widespread. However, little is known about its biology, or indeed the biology of similar algal pathogens. This lack of information hampers our capacity to comprehend the impact of diseases in natural algal populations and, more broadly, on the functioning of marine ecosystems. Additionally, the interplay between natural populations, crops and their pathogens, which are central to the design of management policies concerning any agricultural production, remain entirely unknown for marine seaweeds.

For these reasons, I have developed a laboratory model of Eurychasma and the filamentous brown alga Ectocarpus siliculosus in order to address all these questions.

Work performed

Pathogenicity and immunity, the yin and yang of disease

I have been applying cutting-edge molecular techniques to understand how algae defend themselves against infection, and to identify the infection strategies of its pathogen, Eurychasma. During this project, I have been able to demonstrate that brown algae resort to local cell death in order to contain infection. Specific markers of these responses have been identified and will be useful to further dissect the exact steps of this process at the molecular level.

Main results

Eurychasma genes potentially involved in the infection process have been identified and their functional characterisation has been initiated. Finally, unique biological material has been collected to integrate our data on host specificity with other environmental parameters. In particular, a transcriptomic approach has been initiated in order to investigate the polymorphism of Eurychasma pathogenicity effectors, and to assess the existence of host-pathogen co-evolutionary trends. In the future, this new knowledge will be invaluable to address ecologically relevant questions from a position of strength and novelty.

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