Infection of the brown alga Ectocarpus siliculosus by the oomycete Eurychasma dicksonii induces oxidative stress and halogen metabolism

Abstract

Pathogens are increasingly being recognized as key evolutionary and ecological drivers in marine ecosystems. Defence mechanisms of seaweeds, however, have mostly been investigated by mimicking infection using elicitors. We have established an experimental pathosystem between the genome brown model seaweed E ctocarpus siliculosus and the oomycete E urychasma dicksonii as a powerful new tool to investigate algal responses to infection. Using proteomics, we identified 21 algal proteins differentially accumulated in response to E u. dicksonii infection. These include classical algal stress response proteins such as a manganese superoxide dismutase, heat shock proteins 70 and a vanadium bromoperoxidase. Transcriptional profiling by qPCR confirmed the induction of the latter during infection. The accumulation of hydrogen peroxide was observed at different infection stages via histochemical staining. Inhibitor studies confirmed that the main source of hydrogen peroxide is superoxide converted by superoxide dismutase. Our data give an unprecedented global overview of brown algal responses to pathogen infection, and highlight the importance of oxidative stress and halogen metabolism in these interactions. This suggests overlapping defence pathways with herbivores and abiotic stresses. We also identify previously unreported actors, in particular a Rad23 and a plastid–lipid‐associated protein, providing novel insights into the infection and defence processes in brown algae.

Not in your usual Top 10: protists that infect plants and algae

“…dicksonii . Host genes differentially expressed during infection include those encoding for proteins involved in the detoxification of ROS and halogen metabolism (Strittmatter et al ., ). The host genome includes candidate immune receptors of the leucine‐rich and tetratricopeptide repeat families, which quickly evolve via an original exon shuffling mechanism (Zambounis et al ., ).…”

Transcriptomic insights into innate immunity responding to red rot disease in red alga Pyropia yezoensis

“…Several defense mechanisms have been identified in Phaeophyta such as Ectocarpus siliculosus and Saccharina japonica. E. siliculosus-Eurychasma dicksonii was used as a model of Phaeophyta-oomycete interaction [21,22]. E. siliculosus responds to infection by strengthening the cell wall, producing protease inhibitors, ROS and by halogen metabolism [23,24].…”

Ocean acidification increases iodine accumulation in kelp‐based coastal food webs

“…Iodide efflux occurs under oxidative stress and iodide in the peripheral tissues acts as an inorganic antioxidant to detoxify both aqueous oxidants and ozone, stimulating the release of molecular iodine and volatile iodinated compounds to the atmosphere (Cosse, Potin, & Leblanc, ; Küpper & Kroneck, ). Oxidative burst and associated iodine metabolism also play a direct defensive role in both controlling the growth of potentially pathogenic bacteria living at the thallus surface and scavenging a variety of reactive oxygen species (ROS) (Küpper et al, ; Küpper, Müller, Peters, Kloareg, & Potin, ; Strittmatter et al, ). During oxidative burst, algal cells rapidly release large amounts of activated oxygen species (AOS), such as superoxide (O 2 ‐ ), hydrogen peroxide (H 2 O 2 ), or hydroxyl radicals (OH ‐ ).…”