The infection cushion of Botrytis cinerea: a fungal ‘weapon’ of plant‐biomass destruction

Abstract

The necrotrophic plant-pathogen fungus Botrytis cinerea produces multicellular appressoria dedicated to plant penetration, named infection cushions (IC). A microarray analysis was performed to identify genes upregulated in mature IC. The expression data were validated by RT-qPCR analysis performed in vitro and in planta, proteomic analysis of the IC secretome and biochemical assays. 1231 upregulated genes and 79 up-accumulated proteins were identified. The data support the secretion of effectors by IC: phytotoxins, ROS, proteases, cutinases, plant cell wall-degrading enzymes and plant cell death-inducing proteins. Parallel upregulation of sugar transport and sugar catabolism-encoding genes would indicate a role of IC in nutrition. The data also reveal a substantial remodelling of the IC cell wall and suggest a role for melanin and chitosan in IC function. Lastly, mutagenesis of two upregulated genes in IC identified secreted fasciclin-like proteins as actors in the pathogenesis of B. cinerea. These results support the role of IC in plant penetration and also introduce other unexpected functions for this fungal organ, in colonization, necrotrophy and nutrition of the pathogen.

Transcriptome Profiling Reveals Differential Gene Expression of Secreted Proteases and Highly Specific Gene Repertoires Involved in Lactarius–Pinus Symbioses

“…This appears to be unique to Lactarius so far, as massive up-regulation of sedolisin genes has not been reported in any other ectomycorrhizal fungi ( Kohler et al, 2015 ; Miyauchi et al, 2020 ). Although a regulation of some sedolisin genes was observed in a few plant-interacting fungi, such as the necrotrophic pathogen Botrytis cinerea , their role(s) in the interaction remain largely unknown ( Choquer et al, 2021 ). However, their dramatic up-regulation observed in the present study and the striking expansion in Lactarius genomes ( Looney et al, 2021 ; Lebreton et al, in preparation), both suggest their involvement in Lactarius symbiosis.…”

Clathrin Is Important for Virulence Factors Delivery in the Necrotrophic Fungus Botrytis cinerea

“…Finally, microscopic studies revealed that both the T2.16 and HUB.1 mutants were altered in the production of infection cushions (IC), multicellular appressoria dedicated to the massive secretion of effectors during plant infection ( Mentges et al, 2020 ; Choquer et al, 2021 ). Based on the important role IC play in the virulence of B. cinerea ( de Vallée et al, 2019 ), this default could explain the loss of pathogenicity in these mutants.…”

Multiple knockout mutants reveal a high redundancy of phytotoxic compounds that determine necrotrophic pathogenesis of Botrytis cinerea

“…When incubated on glass surfaces for two days, WT germlings form large aggregates of appressorialike structures, so-called infection cushions. They are believed to represent alternative infection structures to simple appressoria (Choquer et al 2021). Infection cushions with similar morphology were formed by the WT and the 12xpg and 12xbb mutants (Fig.…”