Rantala Anne, Fewer David P, Hisbergues Michael, Rouhiainen Leo, Vaitomaa Jaana, Börner Thomas, Sivonen Kaarina
Department of Applied Chemistry and Microbiology, University of Helsinki, P.O. Box 56, Viikki Biocenter, Viikinkaari 9, FIN-00014, Helsinki, Finland.
Proc Natl Acad Sci U S A. 2004 Jan 13;101(2):568-73. doi: 10.1073/pnas.0304489101. Epub 2003 Dec 30.
Cyanobacteria are a prolific source of secondary metabolites, including compounds with toxic and enzyme-inhibiting activities. Microcystins and nodularins are the end products of a secondary metabolic pathway comprised of mixed polyketide synthases and nonribosomal peptide synthetases. Both peptides are potent natural toxins produced by distantly related genera of cyanobacteria. Horizontal gene transfer is thought to play a role in the sporadic distribution of microcystin producers among cyanobacteria. Our phylogenetic analyses indicate a coevolution of housekeeping genes and microcystin synthetase genes for the entire evolutionary history of the toxin. Hence they do not corroborate horizontal transfer of genes for microcystin biosynthesis between the genera. The sporadic distribution of microcystin synthetase genes in modern cyanobacteria suggests that the ability to produce the toxin has been lost repeatedly in the more derived lineages of cyanobacteria. The data we present here strongly suggest that the genes encoding nodularin synthetase are recently derived from those encoding microcystin synthetase.
蓝藻是次生代谢产物的丰富来源，包括具有毒性和酶抑制活性的化合物。微囊藻毒素和节球藻毒素是由混合聚酮合酶和非核糖体肽合成酶组成的次生代谢途径的终产物。这两种肽都是由远缘蓝藻属产生的强效天然毒素。水平基因转移被认为在微囊藻毒素产生菌在蓝藻中的零星分布中起作用。我们的系统发育分析表明，在毒素的整个进化历史中，管家基因和微囊藻毒素合成酶基因共同进化。因此，它们不支持微囊藻毒素生物合成基因在不同属之间的水平转移。微囊藻毒素合成酶基因在现代蓝藻中的零星分布表明，在蓝藻的更多衍生谱系中，产生毒素的能力已多次丧失。我们在此展示的数据强烈表明，编码节球藻毒素合成酶的基因最近源自编码微囊藻毒素合成酶的基因。
