Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 8, 2008
Publication Date: April 8, 2008
Citation: Proctor, R., Mc Cormick, S.P., Alexander, N.J., Desjardins, A.E. 2008. Variation in nucleotide sequence of TRI1 in 13 trichothecene-producing species of Fusarium: evidence for a complex evolutionary history of a mycotoxin biosynthetic locus [abstract]. European Conference on Fungal Genetics. p. 29. Technical Abstract: Trichothecenes are mycotoxins produced by several genera of fungi, including some agriculturally important Fusarium species. In the two species, Fusarium graminearum and F. sporotrichioides, that have been examined most thoroughly, trichothecene biosynthetic enzymes are encoded at three loci: (1) the 12-gene, core trichothecene biosynthetic gene (TRI) cluster; (2) the TRI1/TRI16 locus; and (3) the TRI101 locus. In F. graminearum, the cytochrome P450 monooxygenase encoded by TRI1 catalyzes trichothecene C-7 and C-8 hydroxylation, whereas in F. sporotrichioides, the enzyme catalyzes only C-8 hydroxylation. Here, nucleotide sequence analysis of 13 Fusarium species distinguished four transpecies groups of TRI1. Within each group, predicted TRI1 amino acid sequences are 85-99% identical, and between groups, sequences are only 65-75% identical. TRI1 sequence variation is not correlated with phylogenetic relationships of Fusarium species inferred by maximum parsimony analysis of nucleotide sequences of beta-tubulin, translation elongation factor, and two core TRI cluster genes. Sequence analysis of TRI1-flanking regions indicated that TRI1 exists in at least three distinct genetic environments. In contrast to variation in TRI1 sequence, these genetic environments are highly correlated with inferred phylogenetic relationships of Fusarium species. Together, these and other data indicate that the evolutionary history of the TRI1/TRI16 locus has been complex and has involved ancestral polymorphism as well as gene relocation, inversion, and nonfunctionalization.