ASSIGNMENT OF SYMBIOTIC DEVELOPMENTAL PHENOTYPES TO COMMON AND SPECIFIC NODULATION (NOD) GENETIC-LOCI OF RHIZOBIUM-MELILOTI
ASSIGNMENT OF SYMBIOTIC DEVELOPMENTAL PHENOTYPES TO COMMON AND SPECIFIC NODULATION (NOD) GENETIC-LOCI OF RHIZOBIUM-MELILOTI
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DOI：
10.1128/jb.168.3.1075-1086.1986
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发表时间：
1986-12-01
影响因子：
3.2
通讯作者：
TRUCHET, G
中科院分区：
文献类型：
--
作者：
DEBELLE, F;ROSENBERG, C;TRUCHET, G
苜蓿根瘤菌特异性侵染和诱导苜蓿生长所需的nod基因已被克隆。转座子Tn 5诱变限定了跨越pSym大质粒的16个酶的三个结区。遗传和细胞学研究62结瘤缺陷突变体允许分配共生发展表型共同和特定的节点位点。根毛卷曲决定共同的（区域I）和特定的（区域III）节点转录单位;位点IIIb（caseH基因）积极控制卷曲的同源宿主苜蓿，而位点IIIa（caseFE）和IIIb（caseH）负控制卷曲的异源主机。区域I（RAC-ABC）是牧羊人弯中细菌渗透和感染线起始所需的，并且RAC-FE转录单元控制苜蓿根毛内的感染线发育。与此相反，根瘤器官发生的诱导，这可以从远处触发，似乎是由共同的nod ABC基因控制，而不需要特定的nod基因nod FE和nod H。区域II影响头发卷曲和感染线形成的效率。
Rhizobium meliloti nodulation (nod) genes required for specific infection and nodulation of alfalfa have been cloned. Transposon Tn5 mutagenesis defined three nod regions spanning 16 kilobases of the pSym megaplasmid. Genetic and cytological studies of 62 nodulation-defective mutants allowed the assignment of symbiotic developmental phenotypes to common and specific nod loci. Root hair curling was determined by both common (region I) and specific (region III) nod transcription units; locus IIIb (nodH gene) positively controlled curling on the homologous host alfalfa, whereas loci IIIa (nodFE) and IIIb (nodH) negatively controlled curling on heterologous hosts. Region I (nodABC) was required for bacterial penetration and infection thread initiation in shepherd''s crooks, and the nodFE transcription unit controlled infection thread development within the alfalfa root hair. In contrast, induction of nodule organogenesis, which can be triggered from a distance, seemed to be controlled by common nodABC genes and not to require specific nod genes nodFE and nodH. Region II affected the efficiency of hair curling and infection thread formation.