Department of Genetics, Forestry and Agricultural Biotechnology Institute, University of Pretoria, South Africa.
Fungal Genet Biol. 2011 Jul;48(7):731-40. doi: 10.1016/j.fgb.2011.03.005. Epub 2011 Mar 29.
Mating type genes are central to sexual reproduction and compatibility in Ascomycete fungi. However the "MAT" loci experience unique evolutionary pressures that can result in rapid divergence and enhanced inter-specific gene-flow (lateral gene transfer). In this study, molecular evolution of MAT loci was considered using the genus Fusarium (Teleomorph: Gibberella) as a model. Both MAT1-1 and MAT1-2 "idiomorphs" from eleven species of the Gibberellafujikuroi species complex were sequenced. Molecular evolution of the MAT loci from these heterothallic (self-sterile) species was compared with that of the MAT loci from nine homothallic (self-fertile) species in the Fusariumgraminearum species complex. Although Fusarium has previously been thought to have the same complement of four MAT genes that are found in Neurospora, we found evidence of a novel gene, MAT1-2-3, that may be specific to the Hypocreales. All MAT genes share a similar set of cis-regulatory motifs, although homothallic species might have recruited novel regulatory elements, which could potentially facilitate alternate expression of MAT1-1-1 and MAT1-2-1. FusariumMAT loci displayed evidence consistent with historical lateral gene-flow. Most notably, the MAT1-1 idiomorph of Fusariumsacchari appears to be unrelated to those of other species in the G.fujikuroi complex. In general, FusariumMAT genes are highly divergent. Both positive selection and relaxed selective constraint could account for this phenomenon. However, the extent of both recombination and inter-specific gene-flow in the MAT locus also appears to affect the rate of divergence.
交配型基因是子囊菌真菌有性生殖和相容性的核心。然而，“MAT”基因座经历了独特的进化压力，这可能导致快速的分化和增强的种间基因流动（水平基因转移）。在这项研究中，以镰孢菌属（有性型：赤霉属）为模型，考虑了 MAT 基因座的分子进化。从 11 种藤仓赤霉菌种复合体的物种中测序了 MAT1-1 和 MAT1-2“同型异型”。比较了这些异宗配合（自交不育）物种的 MAT 基因座的分子进化与 9 种同宗配合（自交可育）物种的 MAT 基因座的分子进化。尽管以前认为镰孢菌具有与曲霉属相同的四个 MAT 基因，但我们发现了一种新基因 MAT1-2-3 的证据，该基因可能是 Hypocreales 特有的。所有 MAT 基因都共享一组相似的顺式调控元件，尽管同宗配合物种可能招募了新的调控元件，这可能有助于 MAT1-1-1 和 MAT1-2-1 的交替表达。镰孢菌 MAT 基因座显示出与历史水平基因流动一致的证据。最值得注意的是，镰孢菌 sacchari 的 MAT1-1 同型异型似乎与藤仓赤霉菌种复合体中的其他物种无关。一般来说，镰孢菌 MAT 基因高度分化。正选择和放松的选择约束都可以解释这种现象。然而，MAT 基因座中的重组和种间基因流动的程度似乎也会影响分化的速度。
