The establishment of symbiosis between leguminous plants and the soil bacteria Rhizobia is investigated using the Nar or spontaneous nodulation phenomenon, i.e. ability of some plant to develop nodulations in the absence of Rhizobium. It is shown that he spontaneous nodule organogenesis is initialized in both Nar and non-Nar plants but more or less blocked further (at the nodule primordia stage...

I this issue of PNAS, Nishimura et al. demonstrate that ASTRAY, the legume homolog of HY5, a transcription factor that mediates light signaling and photomorphogenesis above ground, also affects the interaction between legume roots and their rhizobial endosymbionts underground (1). At first glance, this is a confusing result. What is a transcription factor that mediates light signaling doing reg...

ule formulation are similar to those of secondary root formation (Gresshoff, 1993). Improvements in image Acidic soils can reduce the nodulation of forage legumes. Studies analysis technology allow researchers to assess the efwith a Gilpin series silt loam (fine loamy, mixed mesic, Typic Hapludult) from New, WV, were conducted to determine the effects of lime fects of soil conditions on specifi...

Two methods were developed for the assay of substances stimulatory to the nodulation of bean (Phaseolus vulgaris) roots growing from segments of hypocotyl tissue. Coconut water was the chief source of active material, but extracts of cotyledons, hypocotyls and leaves of beans and of horse chestnut fruits were also stimulatory. High concentrations of nitrate improved nodulation both in the prese...

Ethylene inhibits nodulation in various legumes. In order to investigate strategies employed by Rhizobium to regulate nodulation, the 1-aminocyclopropane-1-carboxylate (ACC) deaminase gene was isolated and characterized from one of the ACC deaminase-producing rhizobia, Rhizobium leguminosarum bv. viciae 128C53K. ACC deaminase degrades ACC, the immediate precursor of ethylene in higher plants. T...

We have used reverse genetics to identify genes involved in legume-rhizobium symbiosis in Lotus japonicus. We obtained the sequences of 20 putative transcription factors from previously reported large-scale transcriptome data. The transcription factors were classified according to their DNA binding domains and patterns of expression during the nodulation process. We identified two homologues of...

Native strains of Bradyrhizobium japonicum were tested for their effectiveness on nodulation, crop yield and nitrogen fixation in soybean (Glycine max). B. japonicum strains were isolated from soybean root nodules collected from different agro-climatic regions of Far Western Nepal, viz. Dipayal (607 m asl), Dadeldhura (1097 m asl), Silgadhi (1209 m asl) and Bajura (1524 m asl). The strains were...

Establishment of the nitrogen-fixing nodulation symbiosis between legumes and rhizobia requires plant-wide reprogramming to allow infection and development of nodules. Nodulation is regulated principally via a mechanism called autoregulation of nodulation (AON). AON is dependent on shoot and root factors and is maintained by the nodulation autoregulation receptor kinase (NARK) in soybean. We de...

Although many aand some b-proteobacterial species are symbiotic with legumes, the evolutionary origin of nitrogenfixing nodulation remains unclear. We examined aand b-proteobacteria whose genomes were sequenced using largescale phylogenetic profiling and revealed the evolutionary origin of two nodulation genes. These genes, nodI and nodJ (nodIJ), play key roles in the secretion of Nod factors, ...

Several soybean genotypes have been identified which specifically exclude nodulation by members of Bradyrhizobium japonicum serocluster 123. We have identified and sequenced a DNA region from B. japonicum strain USDA 110 which is involved in genotype-specific nodulation of soybeans. This 2.3-kilobase region, cloned in pMJS12, allows B. japonicum serocluster 123 isolates to form nodules on plant...