Investigation of the diversity of effector genes in the banana pathogen,Fusarium oxysporum f. sp. cubense,reveals evidence of horizontal gene transfer |
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| Authors: | Elizabeth Czislowski Sam Fraser‐Smith Manuel Zander Wayne T. O'Neill Rachel A. Meldrum Lucy T. T. Tran‐Nguyen Jacqueline Batley Elizabeth A. B. Aitken |
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| Affiliation: | 1. School of Agriculture and Food Sciences, The University of Queensland, St. Lucia, Qld 4072, Australia;2. Biosecurity Queensland, Department of Agriculture and Fisheries, Ecosciences Precinct, Brisbane, Qld 4001, Australia;3. Department of Primary Industry and Resources, Northern Territory Government, Darwin, NT 0801, Australia;4. School of Plant Biology, The University of Western Australia, Crawley, WA 6009, Australia |
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| Abstract: | It is hypothesized that the virulence of phytopathogenic fungi is mediated through the secretion of small effector proteins that interfere with the defence responses of the host plant. In Fusarium oxysporum, one family of effectors, the Secreted In Xylem (SIX) genes, has been identified. We sought to characterize the diversity and evolution of the SIX genes in the banana‐infecting lineages of F. oxysporum f. sp. cubense (Foc). Whole‐genome sequencing data were generated for the 23 genetic lineages of Foc, which were subsequently queried for the 14 known SIX genes (SIX1–SIX14). The sequences of the identified SIX genes were confirmed in a larger collection of Foc isolates. Genealogies were generated for each of the SIX genes identified in Foc to further investigate the evolution of the SIX genes in Foc. Within Foc, variation of the SIX gene profile, including the presence of specific SIX homologues, correlated with the pathogenic race structure of Foc. Furthermore, the topologies of the SIX gene trees were discordant with the topology of an infraspecies phylogeny inferred from EF‐1α/RPB1/RPB2 (translation elongation factor‐1α/RNA polymerase II subunit I/RNA polymerase II subunit II). A series of topological constraint models provided strong evidence for the horizontal transmission of SIX genes in Foc. The horizontal inheritance of pathogenicity genes in Foc counters previous assumptions that convergent evolution has driven the polyphyletic phylogeny of Foc. This work has significant implications for the management of Foc, including the improvement of diagnostics and breeding programmes. |
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| Keywords: | effectors Fusarium oxysporum f. sp. cubense horizontal gene transfer |
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