The Epichloë festucae Antifungal Protein Efe-AfpA Protects Creeping Bentgrass (Agrostis stolonifera) from the Plant Pathogen Clarireedia jacksonii, the Causal Agent of Dollar Spot Disease

Abstract

Dollar spot disease, caused by the fungal pathogen Clarireedia jacksonii, is a major problem in many turfgrass species, particularly creeping bentgrass (Agrostis stolonifera). It is well-established that strong creeping red fescue (Festuca rubra subsp. rubra) exhibits good dollar spot resistance when infected by the fungal endophyte Epichloë festucae. This endophyte-mediated disease resistance is unique to the fine fescues and has not been observed in other grass species infected with other Epichloë spp. The mechanism underlying the unique endophyte-mediated disease resistance in strong creeping red fescue has not yet been established. We pursued the possibility that it may be due to the presence of an abundant secreted antifungal protein produced by E. festucae. Here, we compare the activity of the antifungal protein expressed in Escherichia coli, Pichia pastoris, and Penicillium chrysogenum. Active protein was recovered from all systems, with the best activity being from Pe. chrysogenum. In greenhouse assays, topical application of the purified antifungal protein to creeping bentgrass and endophyte-free strong creeping red fescue protected the plants from developing severe symptoms caused by C. jacksonii. These results support the hypothesis that Efe-AfpA is a major contributor to the dollar spot resistance observed with E. festucae-infected strong creeping red fescue in the field, and that this protein could be developed as an alternative or complement to fungicides for the management of this disease on turfgrasses.

Co‐evolution within the plant holobiont drives host performance

“…In the A. thaliana phyllosphere, the oomycete hub Albugo laibachii affects plant health unless controlled by a lysozyme secreted by the yeast Moesziomyces bullatus (Eitzen et al , 2021 ). Similarly, the bentgrass leaf endophyte Epichloë festucae secretes an antifungal protein that antagonizes the dollar spot pathogen Clarireedia jacksonii (Fardella et al , 2022 ). Upon sugar beet infection by Rhizoctonia solani , root endophytic bacteria prevent disease development by production of antifungal secondary metabolites (Carrión et al , 2019 ).…”

AMAPEC: accurate antimicrobial activity prediction for fungal effector proteins

“…Recently, major efforts were made to develop new functional annotation methods, relying mostly on machine-learning prediction, but these were not aimed to discover antimicrobial activities 58–62 . Following the recent characterization of various fungal effectors with antimicrobial activities 5,28–33 , we aimed to develop a method to predict antimicrobial activity in fungal secretomes and assist discoveries of such proteins across the fungal tree of life.…”

“…The secretomes of plant-associated fungi include diverse carbohydrate-active enzymes (CAZymes) that digest host cell walls, but also small proteins termed “effectors” that promote fungal colonization of plant tissues 24–26 . While modulation of host immunity and, in a broader sense, host physiology was long thought to be the main function of effector proteins 26,27 , recent discoveries of antimicrobial activities displayed by effectors of diverse fungi suggest that microbial antagonism may be one of their key roles as well 5,28–33 . For instance, the plant-pathogenic fungus Verticillium dahliae secretes antimicrobial proteins during both the soil-dwelling stages of its life cycle and during host colonization, to antagonize niche competitors and foster the invasion of both soil and plant tissues 5,29,30 .…”