Abstract
BackgroundRetrotransposons are genetic elements inducing mutations in all domains of life. Despite their detrimental effect, retrotransposons can become temporarily active during epigenetic reprogramming and cellular stress response, which may accelerate host genome evolution. In fungal pathogens, a positive role has been attributed to retrotransposons when shaping genome architecture and expression of genes encoding pathogenicity factors; thus, retrotransposons are known to influence pathogenicity.ResultsWe uncover a hitherto unknown role of fungal retrotransposons as being pathogenicity factors, themselves. The aggressive fungal plant pathogen, Botrytis cinerea, is known to deliver some long-terminal repeat (LTR) deriving regulatory trans-species small RNAs (BcsRNAs) into plant cells to suppress host gene expression for infection. We find that naturally occurring, less aggressive B. cinerea strains possess considerably lower copy numbers of LTR retrotransposons and had lost retrotransposon BcsRNA production. Using a transgenic proof-of-concept approach, we reconstitute retrotransposon expression in a BcsRNA-lacking B. cinerea strain, which results in enhanced aggressiveness in a retrotransposon and BcsRNA expression-dependent manner. Moreover, retrotransposon expression in B. cinerea leads to suppression of plant defence-related genes during infection.ConclusionsWe propose that retrotransposons are pathogenicity factors that manipulate host plant gene expression by encoding trans-species BcsRNAs. Taken together, the novelty that retrotransposons are pathogenicity factors will have a broad impact on studies of host-microbe interactions and pathology.
Highlights
Retrotransposons are genetic elements inducing mutations in all domains of life
The vast majority of B. cinerea small RNAs (BcsRNAs) effectors derive from long-terminal repeat (LTR) retrotransposons [22, 23], raising the hypothesis that retrotransposons could play a role as fungal pathogenicity factors
We analysed previously published sRNA-seq data regarding LTR retrotransposon BcsRNA production in B. cinerea axenic culture grown on agar plates or during infection of the host plants Solanum lycopersicum and Arabidopsis thaliana [23]
Summary
Retrotransposons are genetic elements inducing mutations in all domains of life Despite their detrimental effect, retrotransposons can become temporarily active during epigenetic reprogramming and cellular stress response, which may accelerate host genome evolution. Porquier et al Genome Biology (2021) 22:225 and heterochromatic small interfering RNAs in plants, are produced for retrotransposon control [4, 5] Despite their detrimental effect, retrotransposons become temporarily active during epigenetic reprogramming [6] and cellular stress response [7, 8], which may accelerate host genome evolution [9,10,11,12]. A positive role has been attributed to retrotransposons to shaping genome architecture and expression of genes encoding pathogenicity factors [13, 14]; retrotransposons can influence pathogenicity. The vast majority of BcsRNA effectors derive from long-terminal repeat (LTR) retrotransposons [22, 23], raising the hypothesis that retrotransposons could play a role as fungal pathogenicity factors
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