phrR-Like Gene praR of Azorhizobium caulinodans ORS571 Is Essential for Symbiosis with Sesbania rostrata and Is Involved in Expression of reb Genes
phrR-Like Gene praR of Azorhizobium caulinodans ORS571 Is Essential for Symbiosis with Sesbania rostrata and Is Involved in Expression of reb Genes
复制标题
DOI：
10.1128/aem.00238-10
复制
发表时间：
2010-06-01
影响因子：
4.4
通讯作者：
Oyaizu, Hiroshi
中科院分区：
文献类型：
--
作者：
Akiba, Noriko;Aono, Toshihiro;Oyaizu, Hiroshi
本研究的重点是基因praR的功能，编码一个假定的转录因子Azorhizobium caulinodans ORS 571，一个微型共生田菁rostrata。praR基因是Sinorhizobium medicae WSM 419的phrR基因的同源物，并且praR和phrR同源物分布于整个α变形菌纲。研究了一株固氮菌A. caulinodans praR缺失突变体在自由生活状态下与野生型菌株没有显著差异。然而，由praR突变体形成的茎瘤表现出比野生型茎瘤更低的固氮活性。显微镜检查显示，在由praR突变体形成的结节的早期阶段观察到具有椭圆形或细长形状的感染宿主细胞，但这些感染细胞逐渐分为两种类型。一个保持椭圆形或细长形，但这些细胞中的空泡逐渐扩大，细菌逐渐消失。其他细胞都缩小了，细菌留在里面。基因芯片显示，同源基因的带螺旋Caedibacter reb基因的高度表达的praR突变体。此外，A.与野生型茎瘤相比，缺失praR和reb同源基因的茎瘤突变体表现出高的固氮活性，并且充满了椭圆形或细长的宿主细胞。这些结果表明，PraR控制reb同源基因的表达，reb同源基因的高表达导致A. caulinodans-S.喙虫共生。
This study focuses on the function of the gene praR that encodes a putative transcription factor in Azorhizobium caulinodans ORS571, a microsymbiont of Sesbania rostrata. The praR gene is a homolog of the phrR gene of Sinorhizobium medicae WSM419, and the praR and phrR homologs are distributed throughout the class Alphaproteobacteria. The growth and nitrogen fixation activity of an A. caulinodans praR deletion mutant in the free-living state were not significantly different from those of the wild-type strain. However, the stem nodules formed by the praR mutant showed lower nitrogen fixation activity than the wild-type stem nodules. Microscopy revealed that infected host cells with an oval or elongated shape were observed at early stages in the nodules formed by the praR mutant, but these infected cells gradually fell into two types. One maintained an oval or elongated shape, but the vacuoles in these cells gradually enlarged and the bacteria gradually disappeared. The other cells were shrunken with bacteria remaining inside. Microarrays revealed that genes homologous to the reb genes of Caedibacter taeniospiralis were highly expressed in the praR mutant. Furthermore, the stem nodules formed by an A. caulinodans mutant with a deletion of praR and reb-homologous genes showed high nitrogen fixation activity, comparable to that of the wild-type stem nodules, and were filled with oval or elongated host cells. These results suggest that PraR controls the expression of the reb-homologous genes and that high expression of reb-homologous genes causes aberrance in A. caulinodans-S. rostrata symbiosis.