Cytoskeleton organisation during the infection of three brown algal species, Ectocarpus siliculosus,Ectocarpus crouaniorum and Pylaiella littoralis, by the intracellular marine oomycete Eurychasma dicksonii

Abstract

Oomycete diseases in seaweeds are probably widespread and of significant ecological and economic impact, but overall still poorly understood. This study investigates the organisation of the cytoskeleton during infection of three brown algal species, Pylaiella littoralis, Ectocarpus siliculosus, and Ectocarpus crouaniorum, by the basal marine oomycete Eurychasma dicksonii. Immunofluorescence staining of tubulin revealed how the development of this intracellular biotrophic pathogen impacts on microtubule (MT) organisation of its algal host. The host MT cytoskeleton remains normal and organised by the centrosome until very late stages of the infection. Additionally, the organisation of the parasite's cytoskeleton was examined. During mitosis of the E. dicksonii nucleus the MT focal point (microtubule organisation centre, MTOC, putative centrosome) duplicates and each daughter MTOC migrates to opposite poles of the nucleus. This similarity in MT organisation between the host and pathogen reflects the relatively close phylogenetic relationship between oomycetes and brown algae. Moreover, actin labelling with rhodamine-phalloidin in E. dicksonii revealed typical images of actin dots connected by fine actin filament bundles in the cortical cytoplasm. The functional and phylogenetic implications of our observations are discussed.

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

“…During this stage, the host nucleus and microtubules are still intact (Tsirigoti et al . , ), and a therefore an active host response can be monitored. The comparison of protein profiles revealed 21 spots whose relative abundance varied significantly between healthy and infected Ec.…”

“…dicksonii infection triggers cell wall modifications (Tsirigoti et al . , ). Even though the identification of a vBPO among the 21 differentially expressed proteins of Ec.…”

“…It has recently been demonstrated that a bromoperoxidase is involved in the in vitro cross-linking of phenolic substances and alginate in the presence of H2O2 (Salgado et al 2009), and Eu. dicksonii infection triggers cell wall modifications (Tsirigoti et al 2013(Tsirigoti et al , 2014. Even though the identification of a vBPO among the 21 differentially expressed proteins of Ec.…”

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

“…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]. Laminaria digitate, a model organism in macroalgae immune study, activates ROS [25,26], releases free fatty acid [27], and employs halogen metabolism and defense gene expression [28] in response to bacterial infection.…”

Filamentous brown algae infected by the marine, holocarpic oomyceteEurychasma dicksonii

“…13,14 In our recent publication, we analyze the typical cytoskeleton of a E. dicksonii spore during the different stages of infection. 15 It is clear that the duplication of the MTOC of each spore nucleus precedes the repeated and synchronous divisions. In parallel, we hypothesize that the parasite MTs participate actively in the compartmentalization of the E. dicksonii spores and the formation of the zoosporangium.…”