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Genome Comparisons between Botrytis fabae and the Closely Related Gray Mold Fungus Botrytis cinerea Reveal Possible
Klaus Klug1, Pinkuan Zhu1,2, Patrick Pattar1
1Department of Biology, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany.
Abstract:
While Botrytis cinerea causes gray mold on many plants, its close relative, Botrytis fabae, is host-specifically infecting predominantly faba bean plants. To explore the basis for its narrow host range, a gapless genome sequence of B. fabae strain G12 (BfabG12) was generated. The BfabG12 genome encompasses 45.0 Mb, with 16 chromosomal telomere-to-telomere contigs that show high synteny and sequence similarity to the corresponding B. cinerea B05.10 (BcB0510) chromosomes. Compared to BcB0510, it is 6% larger, due to many AT-rich regions containing remnants of transposable elements, but encodes fewer genes (11,420 vs. 11,707), due to losses of chromosomal segments with up to 20 genes. The coding capacity of BfabG12 is further reduced by nearly 400 genes that had been inactivated by mutations leading to truncations compared to their BcB0510 orthologues. Several species-specific gene clusters for secondary metabolite biosynthesis with stage-specific expression were identified. Comparison of the proteins secreted during infection revealed high similarities, including 17 phytotoxic proteins that were detected in both species. Our data indicate that evolution of the host-specific B. fabae occurred from an ancestral pathogen with wide host range similar to B. cinerea and was accompanied by losses and degeneration of genes, thereby reducing its pathogenic flexibility.
Insights
Botrytis fabae, a faba bean pathogen, evolved from a broad-host ancestor like Botrytis cinerea. Genome analysis reveals gene loss and inactivation reduced its pathogenic flexibility, explaining its narrow host range.
Area of Science:
- Plant pathology
- Genomics
- Fungal genetics
Background:
- Botrytis cinerea causes gray mold on many plants.
- Botrytis fabae is a closely related species with a narrow host range, primarily infecting faba beans.
Purpose of the Study:
- To investigate the genetic basis for the host specificity of Botrytis fabae.
- To compare the genome of B. fabae with B. cinerea to understand evolutionary divergence.
Main Methods:
- Generation of a gapless genome sequence for Botrytis fabae strain G12 (BfabG12).
- Comparative genomic analysis between B. fabae and Botrytis cinerea (BcB0510).
- Analysis of gene content, including gene inactivation and secondary metabolite clusters.
Main Results:
- The BfabG12 genome is 45.0 Mb with high synteny to B. cinerea but is larger due to AT-rich regions.
- B. fabae encodes fewer genes than B. cinerea, with significant gene loss and inactivation (nearly 400 truncated genes).
- Species-specific secondary metabolite gene clusters were identified, and secreted proteins showed high similarity, including 17 shared phytotoxic proteins.
Conclusions:
- Host-specific B. fabae evolved from a wide-host-range ancestor similar to B. cinerea.
- Gene loss, inactivation, and degeneration contributed to reduced pathogenic flexibility and the evolution of host specificity.
