Takeuchi Kasumi, Noda Naomi, Katayose Yuichi, Mukai Yoshiyuki, Numa Hisataka, Yamada Kosumi, Someya Nobutaka
Mol Plant Microbe Interact. 2015 Mar;28(3):333-42. doi: 10.1094/MPMI-09-14-0294-FI.
Two strains of Pseudomonas sp., Os17 and St29, were newly isolated from the rhizosphere of rice and potato, respectively, by screening for 2,4-diacetylphloroglucinol producers. These strains were found to be the same species and were the closest to but different from Pseudomonas protegens among the sequenced pseudomonads, based on 16S ribosomal RNA gene and whole-genome analyses. Strain Os17 was as effective a biocontrol agent as reported for P. protegens Cab57, whereas strain St29 was less effective. The whole-genome sequences of these strains were obtained: the genomes are organized into a single circular chromosome with 6,885,464 bp, 63.5% G+C content, and 6,195 coding sequences for strain Os17; and with 6,833,117 bp, 63.3% G+C content, and 6,217 coding sequences for strain St29. Comparative genome analysis of these strains revealed that the complete rhizoxin analog biosynthesis gene cluster (approximately 79 kb) found in the Os17 genome was absent from the St29 genome. In an rzxB mutant, which lacks the polyketide synthase essential for the production of rhizoxin analogs, the growth inhibition activity against fungal and oomycete pathogens and the plant protection efficacy were attenuated compared with those of wild-type Os17. These findings suggest that rhizoxin analogs are important biocontrol factors of this strain.
通过筛选2,4-二乙酰基间苯三酚产生菌，分别从水稻和马铃薯根际新分离出两株假单胞菌属菌株，Os17和St29。基于16S核糖体RNA基因和全基因组分析，发现这些菌株属于同一物种，在已测序的假单胞菌中与荧光假单胞菌最为接近但又有所不同。菌株Os17作为生防菌的效果与报道的荧光假单胞菌Cab57相当，而菌株St29的效果较差。获得了这些菌株的全基因组序列：Os17菌株的基因组由一条单环染色体组成，大小为6,885,464 bp，G+C含量为63.5%，有6,195个编码序列；St29菌株的基因组大小为6,833,117 bp，G+C含量为63.3%，有6,217个编码序列。对这些菌株的比较基因组分析表明，在Os17基因组中发现的完整根霉素类似物生物合成基因簇（约79 kb）在St29基因组中不存在。在一个缺乏根霉素类似物生产所必需的聚酮合酶的rzxB突变体中，与野生型Os17相比，其对真菌和卵菌病原体的生长抑制活性以及植物保护效果均有所减弱。这些发现表明根霉素类似物是该菌株重要的生防因子。
