Department of Microbiology, North Carolina State University, Raleigh, North Carolina 27695-7615, and Nitrogen Fixation and Soybean Genetics Laboratory, Plant Physiology Institute, Beltsville Agricultural Research Center, Agricultural Research Service, Beltsville, Maryland 20705.
Appl Environ Microbiol. 1986 Mar;51(3):477-80. doi: 10.1128/aem.51.3.477-480.1986.
DNAs from Bradyrhizobium japonicum USDA 110 derivatives that differ in nitrogen-fixing ability produced similar electrophoretic patterns with five different restriction enzymes. Our data support the hypothesis of common ancestry for these derivatives. Derivatives I-110 and L1-110 differed as much as 100-fold in acetylene reduction activity when they were tested with several soybean cultivars in both greenhouse and field experiments. While possessing nodulating ability, derivative L1-110 is deficient in symbiotic nitrogen-fixing ability, whereas derivative I-110 is symbiotically competent. Hybridization of nifDK and nifH probes from B. japonicum to Southern blots of restricted DNAs from strain USDA 110 derivatives produced similar patterns. This finding indicates similar structural gene organization for both derivative I-110 and derivative L1-110 and implies that the difference in symbiotic nitrogen fixation is probably not due to structural gene rearrangements. However, our hybridization data do not rule out the possibility of differences in expression of structural nif genes or alterations in the structure or expression of other genes required for symbiotic nitrogen fixation.
来自固氮根瘤菌 USDA 110 衍生物的 DNA，其固氮能力不同，用五种不同的限制酶产生相似的电泳图谱。我们的数据支持这些衍生物具有共同祖先的假设。衍生物 I-110 和 L1-110 在温室和田间试验中用几种大豆品种进行乙炔还原活性测试时，差异高达 100 倍。虽然具有结瘤能力，但衍生物 L1-110 在共生固氮能力上存在缺陷，而衍生物 I-110 则具有共生能力。从 B. japonicum 提取的 nifDK 和 nifH 探针与来自 USDA 110 衍生物的限制 DNA 的 Southern 印迹杂交产生相似的模式。这一发现表明衍生物 I-110 和衍生物 L1-110 的结构基因组织相似，这意味着共生固氮的差异可能不是由于结构基因重排引起的。然而，我们的杂交数据并不能排除结构 nif 基因表达的差异或共生固氮所需的其他基因结构或表达的改变的可能性。
