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Interspecific transfer of host-specific toxin genes in Stagonospora nodorum

Oliver, R.P., Solomon, P.S., Hane, J., Stukenbrock, E.H., McDonald, B.A., Liu, Z., Faris, J.D. and Friesen, T.L. (2007) Interspecific transfer of host-specific toxin genes in Stagonospora nodorum. In: XXIV Fungal Genetics Conference, 20 - 25 March, Pacific Grove, California, USA.


The host-specific toxin ToxA, produced by P. tritici-repentis, confers virulence on wheat genotypes carrying Tsn1. The Stagonospora nodorum gene, SnToxA was identified from a reannotation of the genome sequence and is nearly identical to PtrToxA. Disruption of SnToxA reduced disease on wheat lines carrying Tsn1. ToxA genes from a large isolate collection from P. tritici-repentis were identical but those from S. nodorum were highly variable. P. tritici-repentis was first identified in 1902 but it was not until 1941 that typical tan spot symptoms were first described. Nowadays, P. tritici- repentis is a regular and abundant pathogen. Our evidence strongly suggests that ToxA was horizontally transferred to P. tritici-repentis some time prior to 1941. These new forms appear to have rapidly spread around the world, probably in grain shipments (Nature Genetics 38 953-956). Our work indicates that S. nodorum produces several other toxins. The presence of multiple host-specific toxins and their transfer between species raises many interesting evolutionary questions; 1. How does toxin possession and expression affect the fecundity of fungal strains carrying the toxins? 2. How can we explain the expression of toxin receptor genes? 3.What are the mechanisms of sequence diversification in toxin genes?

Item Type: Conference Item
Murdoch Affiliation(s): Australian Centre for Necrotrophic Fungal Pathogens
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