Cloutler J, Laberge S, Castonguay Y, Antoun H
Recherche en sciences de la vie et de la sante, Université Laval, Québec, Canada.
Mol Plant Microbe Interact. 1996 Nov;9(8):720-8. doi: 10.1094/mpmi-9-0720.
We have shown, by sequencing the nodulation gene region of Rhizobium sp. strain N33 previously isolated from the Canadian high arctic, that the nodHPQ genes are located in a 4.8-kb region downstream of nodBCIJ. The open reading frames of nodHPQ are 747, 906, and 1941 nucleotides long, respectively. The strain N33 genome contains one copy of nodH and two copies of nodPQ that are homologous to those genes in Rhizobium meliloti. Tn5 insertions in the nodHPQ genes of strain N33 did not affect the formation of nodules on the two homologous hosts, Astragalus cicer and Onobrychis viciifolia. Since strain N33 contains the nodBCIJHPQ genes and the recently sequenced nodAFEG genes, we looked for similar host range with R. meliloti. Strain N33 and R. meliloti strains A2 and RCR2011 were shown to induce the formation of root nodules on plants of O. viciifolia. However, strain N33, compared with R. meliloti strains, was able to elicit a few, white, empty, root nodules on Medicago sativa. R. meliloti strains, compared with strain N33, were shown to induce only few nodules containing bacteria on A. cicer. Induction of nod genes transcription in strain N33 was shown to be induced by a variety of flavonoid compounds that are different from those inducing nod genes from R. meliloti.
我们通过对先前从加拿大高北极地区分离出的根瘤菌属菌株N33的结瘤基因区域进行测序，发现nodHPQ基因位于nodBCIJ下游4.8 kb的区域。nodHPQ的开放阅读框分别长747、906和1941个核苷酸。菌株N33的基因组包含一个nodH拷贝和两个nodPQ拷贝，它们与苜蓿根瘤菌中的那些基因同源。N33菌株的nodHPQ基因中的Tn5插入并不影响在两个同源宿主鹰嘴紫云英和红豆草上形成根瘤。由于菌株N33含有nodBCIJHPQ基因和最近测序的nodAFEG基因，我们寻找了与苜蓿根瘤菌相似的宿主范围。结果表明，菌株N33和苜蓿根瘤菌菌株A2及RCR2011能诱导红豆草植株形成根瘤。然而，与苜蓿根瘤菌菌株相比，菌株N33能够在紫花苜蓿上引发一些白色的、空的根瘤。与菌株N33相比，苜蓿根瘤菌菌株在鹰嘴紫云英上仅诱导出少数含细菌的根瘤。结果表明，菌株N33中结瘤基因的转录由多种类黄酮化合物诱导，这些化合物与诱导苜蓿根瘤菌结瘤基因的化合物不同。
