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首页> 外文期刊>Applied and Environmental Microbiology >Expression of Nodulation Genes in Rhizobium leguminosarum biovar trifolii Is Affected by Low pH and by Ca and Al Ions
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Expression of Nodulation Genes in Rhizobium leguminosarum biovar trifolii Is Affected by Low pH and by Ca and Al Ions

机译:低pH值和Ca和Al离子影响豆科根瘤菌根瘤中结瘤基因的表达。

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Early stages in the infection of leguminous plants by Rhizobium spp. are restricted at low pH and are further influenced by the presence of Ca and Al ions. In the experiments reported here, transcriptional and translational fusions of the Escherichia coli lacZ gene to Rhizobium leguminosarum biovar trifolii nodulation (nod) genes were used to investigate the effects of pH and of Ca and Al ions on nod gene expression. The regulatory nodD gene in R. leguminosarum biovar trifolii was constitutively expressed at a range of pH levels between 4.8 and 6.5, and expression was not affected by the addition of 22.5 μM Al or 1,250 μM Ca. Induction of expression of nodA, nodF, and region II nodulation genes in the presence of 5 × 10?7 M 7,4′-dihydroxyflavone was restricted at a pH of nodA expression was further restricted by 22.5 μM Al over a range of pH levels but was increased in the presence of Ca. The addition of Ca, however, only slightly alleviated the Al-mediated inhibition of nodA induction. Induction of expression of nodA was equally sensitive to low pH in three strains of R. leguminosarum biovar trifolii (ANU845, ANU815, and ANU1184), which exhibited contrasting growth abilities in solution culture at a pH of nodA in these three strains, with the most Al-tolerant strain for growth being the most Al-sensitive strain for nod gene induction. Poor induction of expression of nodulation genes in R. leguminosarum biovar trifolii was considered to be an important factor contributing to the acid-sensitive step of legume root infection.
机译:根瘤菌感染豆科植物的早期阶段。在低pH值时会受到限制,并且会进一步受到Ca和Al离子的影响。在此处报道的实验中,大肠杆菌lacZ基因与豆科根瘤菌生物变种节结(nod)基因的转录和翻译融合被用于研究pH以及Ca和Al离子对nod基因表达的影响。在4.8至6.5范围内的pH水平范围内,豆科植物变种三叶草中的调节性nodD基因组成性表达,且添加22.5μMAl或1,250μMCa不会影响表达。在5×10?7 M 7,4'-二羟基黄酮的存在下,nodA,nodF和II区结节基因表达的诱导在nodA的pH值下受到限制,在一定pH值范围内,22.5μMAl进一步限制了表达但在钙的存在下增加。然而,Ca的添加仅稍微减轻了Al介导的对nodA诱导的抑制。 nodA表达的诱导对三株豆科植物豆腐变种三叶草(ANU845,ANU815和ANU1184)的低pH值同样敏感,在这三株菌株中,在nodA的pH值下,溶液培养显示出相反的生长能力。用于生长的耐铝菌株是用于nod基因诱导的对铝最敏感的菌株。豆科植物根瘤菌(R. leguminosarum biovar trifolii)中结瘤基因表达的诱导不良被认为是导致豆科植物根部感染酸敏感步骤的重要因素。

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