Distribution of 2,4-Diacetylphloroglucinol Biosynthetic Genes among the Pseudomonas spp. Reveals Unexpected Polyphyletism
Distribution of 2,4-Diacetylphloroglucinol Biosynthetic Genes among the Pseudomonas spp. Reveals Unexpected Polyphyletism
复制标题
DOI：
10.3389/fmicb.2017.01218
复制
发表时间：
2017-06-30
影响因子：
5.2
通讯作者：
Muller, Daniel
中科院分区：
文献类型：
--
作者：
Almario, Juliana;Bruto, Maxime;Muller, Daniel
通过产生2，4-二乙酰基间苯三酚（DAPG）保护植物根免受植物病原体侵害的荧光假单胞菌被认为形成由“荧光假单胞菌”组的“波纹假单胞菌”和“蛋白假单胞菌”亚组中的DAPG（+）假单胞菌菌株组成的单系谱系。然而，这两个亚群中的许多种的DAPG生产能力尚未被研究，并且DAPG（+）假单胞菌是否真正是单系的仍有待验证。因此，DAPG生物合成操纵子（phlACBD基因）在假单胞菌属中的分布。在测序的基因组和模式菌株中进行了研究。结果显示，DAPG（+）假单胞菌包括“荧光假单胞菌”组的种，即，Protegens、P. brassicacearum、P. kilonensis和P. thivervalensis，以及P. gingeri，其中没有记录。令人惊讶的是，它们还包括“荧光假单胞菌”组以外的细菌，如假单胞菌属OT 69，甚至包括两个β-变形菌属。基于phl操纵子的系统发育树与从串联的管家基因rpoB、gyrB和rrs推断的系统发育树基本一致。与目前的假设不同，祖先性格重建倾向于多个独立的收购，而不是一个祖先事件后的垂直遗传。事实上，基于同线性分析，这些收购似乎有所不同，根据假单胞菌亚组，甚至亚组内的系统发育组。总之，我们的研究表明，phl（+）假单胞菌种群形成了一个多系群，并表明DAPG的生物合成可能不限于该属。在评估根际生态系统中phl（+）细菌种群的生态学意义时，这一点很重要。
Fluorescent pseudomonads protecting plant roots from phytopathogens by producing 2,4-diacetylphloroglucinol (DAPG) are considered to form a monophyletic lineage comprised of DAPG(+) Pseudomonas strains in the "P. corrugata" and "P. protegens" subgroups of the "Pseudomonas fluorescens" group. However, DAPG production ability has not been investigated for many species of these two subgroups, and whether or not the DAPG(+) Pseudomonas are truly monophyletic remained to be verified. Thus, the distribution of the DAPG biosynthetic operon (phlACBD genes) in the Pseudomonas spp. was investigated in sequenced genomes and type strains. Results showed that the DAPG(+) Pseudomonas include species of the "P. fluorescens" group, i.e., P. protegens, P. brassicacearum, P. kilonensis, and P. thivervalensis, as expected, as well as P. gingeri in which it had not been documented. Surprisingly, they also include bacteria outside the "P. fluorescens" group, as exemplified by Pseudomonas sp. OT69, and even two Betaproteobacteria genera. The phl operon-based phylogenetic tree was substantially congruent with the one inferred from concatenated housekeeping genes rpoB, gyrB, and rrs. Contrariwise to current supposition, ancestral character reconstructions favored multiple independent acquisitions rather that one ancestral event followed by vertical inheritance. Indeed, based on synteny analyses, these acquisitions appeared to vary according to the Pseudomonas subgroup and even the phylogenetic groups within the subgroups. In conclusion, our study shows that the phl(+) Pseudomonas populations form a polyphyletic group and suggests that DAPG biosynthesis might not be restricted to this genus. This is important to consider when assessing the ecological significance of phl(+) bacterial populations in rhizosphere ecosystems.