Liu Siwen, Wu Bo, Lv Shuxia, Shen Zongzhuan, Li Rong, Yi Ganjun, Li Chunyu, Guo Xiuwu
College of Horticulture, Shenyang Agricultural University, Shenyang, China.
Key Laboratory of South Subtropical Fruit Biology and Genetic Resource Utilization, Ministry of Agriculture, Key Laboratory of Tropical and Subtropical Fruit Tree Research of Guangdong Province, Institution of Fruit Tree Research, Guangdong Academy of Agricultural Sciences, Guangzhou, China.
Front Plant Sci. 2019 Sep 4;10:1069. doi: 10.3389/fpls.2019.01069. eCollection 2019.
Fusaric acid (FA) is an important secondary metabolite of many Fusarium species and involved in the wilt symptoms caused in banana by f. sp. . To investigate the evolution characteristics of the 12 FA biosynthetic genes (), coding sequences of the 12 genes and three housekeeping genes, α (translation elongation factor-1α/RNA polymerase II subunit I/RNA polymerase II subunit II), were subjected to genetic diversity analysis, phylogenetic analysis, recombination detection, and selective pressure analysis. The results of selective pressure analysis showed that the 15 genes were mainly subjected to negative selection. However, a significantly higher number of silent mutations, which could not be simply explained by selective pressure difference, were observed in the 12 genes in than in the three housekeeping genes. Infraspecies phylogeny and recombination detection analysis showed that significantly more horizontal gene transfer (HGT) events (normalized) had occurred in the genes than in the three housekeeping genes. In addition, many of these events involved outgroup isolates and significantly increased the genetic diversity of genes in . The infraspecies phylogenetic analysis suggested that the polyphyletic phylogeny proposed for Foc requires further discussion, and the divergence of race 1, race 4, and the common ancestor of several () isolates pathogenic to nonbanana plants should have diverged over a short period. Finally, our results suggest that the genes in should have benefited from HGT to gain a relatively high genetic diversity to respond to different host plants and environments despite mainly being subject to negative selection.
镰刀菌酸（FA）是许多镰刀菌属物种的一种重要次生代谢产物，与尖孢镰刀菌古巴专化型（Foc）引起的香蕉枯萎症状有关。为了研究12个FA生物合成基因（FAS基因）的进化特征，对这12个基因以及3个看家基因α（翻译延伸因子-1α/RNA聚合酶II亚基I/RNA聚合酶II亚基II）的编码序列进行了遗传多样性分析、系统发育分析、重组检测和选择压力分析。选择压力分析结果表明，这15个基因主要受到负选择。然而，在尖孢镰刀菌古巴专化型的12个FAS基因中观察到的沉默突变数量明显高于3个看家基因，这不能简单地用选择压力差异来解释。种内系统发育和重组检测分析表明，FAS基因中发生的水平基因转移（HGT）事件（标准化后）明显多于3个看家基因。此外，许多这些事件涉及外群分离株，并显著增加了尖孢镰刀菌古巴专化型中FAS基因的遗传多样性。种内系统发育分析表明，针对尖孢镰刀菌古巴专化型提出的多系系统发育需要进一步讨论，1号生理小种、4号生理小种以及几种对非香蕉植物致病的尖孢镰刀菌（Foc）分离株的共同祖先应该在短时间内发生了分化。最后，我们的结果表明，尽管尖孢镰刀菌古巴专化型中的FAS基因主要受到负选择，但它们应该从水平基因转移中受益，从而获得相对较高的遗传多样性，以应对不同的寄主植物和环境。
