Interaction between the cell walls of microalgal host and fungal carbohydrate‐activate enzymes is essential for the pathogenic parasitism process

Abstract

Fungi can parasitize microalgae, exerting profound impacts on both the aquatic ecosystems and microalgal mass cultures. In this study, the unicellular green alga Haematococcus pluvialis and the blastocladialean fungus Paraphysoderma sedebokerense were used as a model system to address the mechanisms underlying the fungal parasitism on the algal host. High-throughput metabolic assay indicated that P. sedebokerense can utilize several carbon sources with a preference for mannose, glucose and their oligosaccharides, which was compatible with the profile of the host algal cell walls enriched with glucan and mannan. The results of dual transcriptomics analysis suggested that P. sedebokerense can upregulate a large number of putative carbohydrate-activate enzymes (CAZymes) encoding genes, including those coding for the endo-1,4-β-glucanase and endo-1,4-β-mannanase during the infection process. The cell walls of H. pluvialis can be decomposed by both P. sedebokerense and commercial CAZymes (e.g. cellulase and endo-1,4-β-mannanase) to produce mannooligomers, while several putative parasitismrelated genes of P. sedebokerense can be in turn upregulated by mannooligomers. In addition, the parasitism can be blocked by interfering the selected CAZymes including glucanase, mannanase and lysozyme with the specific inhibitors, which provided a framework for screening suitable compounds for pathogen mitigation in algal mass culture.

Physiological and Dual Transcriptional Analysis of Microalga Graesiella emersonii–Amoeboaphelidium protococcarum Pathosystem Uncovers Conserved Defense Response and Robust Pathogenicity

“…Knowledge about the isolation, identification, and progression of algal parasites is currently growing [ 7 ]. However, the underlying mechanisms of algal infection by fungal parasites remain largely unknown due to the lack of stable pathosystems for laboratory investigations [ 8 , 9 ].…”

Fenton Reaction Facilitates The Fungal Infection On The Unicellular Alga Haematococcus Pluvialis and Discovery of a Biosafe and Environment-Friendly Chemical That Blocks The Infection

“…Strains and culturing conditions H. pluvialis cells were maintained in our laboratory (Lin et al, 2021) and cultured in the BG11 growth medium at 21-23°C under continuous illumination (20 μmol•m -2 •s -1 ). The fungal parasite P. sedebokerense used in this study was isolated in the previous study (Lin et al, 2021).…”

“…Strains and culturing conditions H. pluvialis cells were maintained in our laboratory (Lin et al, 2021) and cultured in the BG11 growth medium at 21-23°C under continuous illumination (20 μmol•m -2 •s -1 ). The fungal parasite P. sedebokerense used in this study was isolated in the previous study (Lin et al, 2021). P. sedebokerense cells were grown in the fungal growth medium supplemented with yeast extract and peptone (Hoffman et al, 2008) on an orbital shaker at a speed of 150 rpm maintained at 30°C.…”

“…Heat-stable recognition sites on the algal cell were necessary for the fungal attachment and encystment, while signal transduction in H. pluvialis cells was obligated for the fungal sporangium development and epidemic (Asatryan et al, 2019). Interaction between the cell walls of H. pluvialis and carbohydrate activated enzymes in P. sedebokerense was believed to be essential for the parasitism process (Lin et al, 2021). These studies are focused on the speci c recognition of H. pluvialis cells by P. sedebokerense and the warfare between them during the early-stage of infection, but little is known for the mechanisms underlying the post-infection process, especially for the fast material degradation in algal cells.…”

Physiological and Dual Transcriptional Analysis of Microalga Graesiella Emersonii–Amoeboaphelidium Protococcarum Pathosystem Uncovers Conserved Defense Response and Robust Pathogenicity

“…Knowledge about the isolation, identi cation, and progression of algal parasites is currently growing [7]. However, the underlying mechanisms of algal infection by fungal parasites remain largely unknown due to the lack of stable pathosystems for laboratory investigations [8,9]. The oleaginous microalga Graesiella emersonii is an industrial strain for lipid production [10], but it is frequently infected by endoparasite Amoeboaphelidium protococcarum belonging to the class Aphelidea.…”