The purB gene controls rhizosphere colonization by Pantoea agglomerans
The purB gene controls rhizosphere colonization by Pantoea agglomerans
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DOI：
10.1111/j.1472-765x.2009.02779.x
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发表时间：
2010-02-01
影响因子：
2.4
通讯作者：
Nautiyal, C. S.
中科院分区：
文献类型：
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作者：
Chauhan, P. S.;Nautiyal, C. S.
目的：分离Pantoea agglomerans NBRISRM （SRM）根际能力缺陷转座子Tn5突变体，并鉴定导致其根定植能力缺陷的基因。方法和结果：从5000多个含有Tn5的无性系中，选择了一个突变体P. agglomerans NBRISRMT (SRMT)，与SRM相比，其定植量减少了6个log单位，经过30天的砂-非无菌土壤试验系统，进一步研究了该突变对根际能力的影响。SRMT限制性基因组DNA的Southern杂交分析表明，该突变体具有单个Tn5插入。SRM滴度增加到约2 × 108 CFU g-1根，而异养菌的本地细菌种群约为5 × 107 CFU g-1根。相比之下，30天后，在1 × 102 CFU g-1根中，SRMT的滴度几乎无法检测到，表明其无法存活并定植根际。对Tn5突变体侧翼区域的测序显示，Tn5破坏了purB基因。结论：SRMT定植表型的缺陷是由于pur B基因编码的腺苷酸琥珀酸裂解酶（EC 4.3.2.2）的破坏，该酶是聚团草根际定植所必需的。由于purB基因的破坏，与SRM相比，SRMT形成的胞外多糖和生物膜明显减少。研究的意义和影响：本研究首次证明了purB基因在根际能力和根定植中的功能作用。
Aims:To isolate the rhizosphere competence-defective transposon Tn5 mutant of Pantoea agglomerans NBRISRM (SRM) and to identify the gene causing defect in its root colonization ability.Methods and Results:From over 5000 clones containing Tn5, one mutant P. agglomerans NBRISRMT (SRMT) showing 6 log units less colonization when compared with SRM, after 30 days in sand-nonsterilized soil assay system was selected for further work to determine the effects of the mutation on rhizosphere competence. Southern hybridization analysis of restricted genomic DNA of SRMT demonstrated that the mutant had a single Tn5 insert. SRM increased in titre to about 2 x 108 CFU g-1 root, compared with the indigenous bacterial population of heterotrophs of about 5 x 107 CFU g-1 root. In contrast, 30 days later, the titre value of SRMT was almost undetectable at 1 x 102 CFU g-1 root, demonstrating its inability to survive and colonize the rhizosphere. Sequencing of the flanking region of the Tn5 mutant revealed that Tn5 disrupted the purB gene.Conclusions:A defect in the colonization phenotype of the SRMT was attributed to the disruption in adenylosuccinate lyase (EC 4.3.2.2) which is encoded by the pur B gene and is required for rhizosphere colonization in P. agglomerans. Significantly less exopolysaccharide and biofilm was formed by SRMT when compared to SRM, because of the disruption of the purB gene.Significance and Impact of the Study:This work provides the first evidence for a functional role of purB gene in rhizosphere competence and root colonization by any rhizobacteria.