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首页> 外文期刊>Molecular ecology >Diversity of microcystin genotypes among populations of the filamentous cyanobacteria Planktothrix rubescens and Planktothrix agardhii
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Diversity of microcystin genotypes among populations of the filamentous cyanobacteria Planktothrix rubescens and Planktothrix agardhii

机译：丝状蓝藻浮游植物和浮游藻琼脂种群中微囊藻毒素基因型的多样性

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Microcystins (MCs) are toxic heptapeptides that are produced by filamentous cyanobacteria Planktothrix rubescens and Planktothrix agardhii via nonribosomal peptide synthesis. MCs share a common structure cyclo (-D-Alanine(1)-L-X-2- D-erythro-ss-iso-aspartic acid(3)-L-Z(4)-Adda(5)-D-Glutamate(6)- N-methyl-dehydroalanine(7)) where X-2 and Z(2) are variable L-amino acids in positions 2, 4 of the molecule. Part of the mcyB gene (1,451 bp) that is involved in the activation of the X-2 amino acid during MC synthesis was sequenced in 49 strains containing different proportions of arginine, homotyrosine, and leucine in position 2 of the MC molecule. Twenty-five genotypes were found that consisted of eight genotype groups (A-H, comprising 2-11 strains) and 17 unique genotypes. P. rubescens and P. agardhii partly consisted of the same mcyB genotypes. The occurrence of numerous putative recombination events that affected all of the genotypes can explain the conflict between taxonomy and mcyB genotype distribution. Genotypes B (homotyrosine and leucine in X-2) and C (arginine in X-2) showed higher nonsynonymous/synonymous (d(N)/d(S)) substitution ratios implying a relaxation of selective constraints. In contrast, other genotypes (arginine, leucine, homotyrosine) showed lowest d(N)/d(S) ratios implying purifying selection. Restriction fragment length polymorphism (RFLP) revealed the unambiguous identification of mcyB genotypes, which are indicative of variable X-2 amino acids in eight populations of P. rubescens in the Alps (Austria, Germany, and Switzerland). The populations were found to differ significantly in the proportion of specific genotypes and the number of genotypes that occurred over several years. It is concluded that spatial isolation might favour the genetic divergence of microcystin synthesis in Planktothrix spp.
机译：微囊藻毒素（MCs）是有毒的七肽，是由丝状蓝细菌兰氏浮游生物和琼脂浮游生物通过非核糖体肽合成产生的。 MC共有一个共同结构的环（-D-丙氨酸（1）-LX-2-D-赤藓基-异天冬氨酸（3）-LZ（4）-Adda（5）-D-谷氨酸（6）- N-甲基-脱氢丙氨酸（7），其中X-2和Z（2）是分子第2、4位的可变L-氨基酸。 MC合成过程中涉及X-2氨基酸活化的部分mcyB基因（1,451 bp）在49个菌株中进行了测序，该菌株在MC分子的2位含有不同比例的精氨酸，高酪氨酸和亮氨酸。发现了由八个基因型组（A-H，包括2-11个菌株）组成的二十五个基因型和17个独特的基因型。风疹假单胞菌和琼脂假单胞菌部分地由相同的mcyB基因型组成。影响所有基因型的众多推定的重组事件的发生可以解释分类学和mcyB基因型分布之间的冲突。基因型B（X-2中的酪氨酸和亮氨酸）和C（X-2中的精氨酸）显示出更高的非同义/同义（d（N）/ d（S））取代比，这意味着选择性约束的放松。相反，其他基因型（精氨酸，亮氨酸，高酪氨酸）显示出最低的d（N）/ d（S）比，这意味着纯化选择。限制性片段长度多态性（RFLP）揭示了mcyB基因型的明确鉴定，其指示了阿尔卑斯山（奥地利，德国和瑞士）的八个红斑假单胞菌种群中可变的X-2氨基酸。发现这些人群在特定基因型的比例和几年内发生的基因型数量上有显着差异。结论是，空间隔离可能有利于Planktothrix spp中微囊藻毒素合成的遗传差异。

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