• Applied Biological Chemistry
• /
• v.40 no.6
• /
• pp.546-550
• /
• 1997

This study was carried out to elucidate the biological characteristics of Rhizobia in biological nitrogen fixation system. The results of investigation were as follows; Polyacrylamide gel electrophoresis pattern of root lectin in the presence of SDS was ascertained electrophoretically and chromatographically. The purified root lectin formed immunoprecipitin line with anti lectin rabbit IgG. Root lectin, seed lectin and root exudate were tested for chemotactic ability. Chemotactic responses of RCR3407 and KCTC2422 toward root exudate were stronger than those of seed lectin and root lectin, but there didn't occur chemotactic responses of LPN100, not bound with seed lectin and that of LPN101, bound with seed lectin toward root exudate, root lectin and seed lectin. RCR3407, KCTC2422 and LPN-101, which nodulated with soybean, interacted with soybean lectin, but not with pea lectin. LPN-100, which was not nodulated with soybean, didn't interact with soybean lectin.

• Korean journal of applied entomology
• /
• v.22 no.4 s.57
• /
• pp.293-299
• /
• 1983

Experiments were carried out to elucidate the specific interactions between host plant, Phaseolus vulgaris, and symbiotic bacteria, Rhizobium Phaseoli. Purified P. vulgaris lectins and six species of cultured Rhizobium were subjected to agglutination test. Lectins from bean and R. phaseoli showed relatively high agglutination activity indicating that host plant lectins recognize carbohydrate moieties on the compatible Rhizobium cell surface. The specific carbohydrate receptors for binding of the lectins on the cell surface of R. phaseoli were found as mannose and galactose. The minimum concentration of sugars for the inhibition was 6.25mM. The lectin content of cultured plant roots was measured after germination and was maximum in 5-day seedlings. The nodulation was competitively inhibited by lectins for the plants cultured with Rhizobium cells. By immunochemical studies, there was some relationship in antigenic determinants between R. phaseoli and R. japonicum but no relationships were observed with other Rhizobium species. The results suggest that the infection by rhizobia to the roots of leguminous plants may be caused by the specific interaction of lectins with rhizobia.

• Korean Journal of Weed Science
• /
• v.12 no.1
• /
• pp.16-30
• /
• 1992

A field experiment was done to evaluate the growth response, rhizobia nodulation and vesicular-arbuscular mycorrhizal fungi (VAMF) infection of soybean treated with the different concentration of three-herbicides, alachlor, simazine, linuron. The results obtained were summarized as follows ; Emergence rate of soybean was non-significantly decreased by increasing the herbicide concentration. In simazine treatment, low emergence rate showed even in recommended concentration, especially the lowest emergence rate in treble concentration of recommended dose was about 50%. The plant length of soybean lowered by increasing the herbicide concentration, but there were almost no differences in recommended dose. Particularly that in a high concentration of herbicides at three weeks after treatment(WAT) was decreased remarkably. In the plant diameter of soybean shoot, no differences in the recommended concentration of alachlor and linuron at 2 WAT, but those of recommended dose was decreased with the lapse of time, and the lowest treatment was simazine-treated plot. Leaf area and fresh weight of soybean tended to decrease over the control even in recommended concentration and it was decreased with the increment of the herbicide dose. Yield component, fresh weight of rhizobia nodule and chlorophyll content of soybean leaves were reduced with the increment of herbicide dose, espicially remarkable tendency was revealed in simazine-treated plot. Seasonal infection rate of VAM showed a slight decrease by increasing of herbicide dose, and the lowest infection was simazine treatment. Significant correlation was realized among the reduction of rhizobia nodulation, VAM colonization and the agronomic characters of soybean and it was considered that the reduction of rhizobia nodulation and VAM colonization by misapplication of the herbicides might be a causal factor for decrease in soybean yield.

• The Plant Pathology Journal
• /
• v.20 no.1
• /
• pp.18-21
• /
• 2004

The root hair provides a major entering spot for the symbiotic legume rhizobia. It is obvious that dynamic cell wall modification occurs in the plant root hair during the early microbe invasion. Expansins are nondestructive cell wall-modifying proteins that are involved in cell growth and differentiation. Among about 40 expansin genes in Arabidopsis, two expansin genes are expressed specifically in the root hair cell. Orthologous genes of this Arabidopsis root hair expansins have been found in other Brassica members, rice, and Medicago truncatula (a legume). In this review, I discuss the probable function of expansins during the early symbiotic process between the root hair and microbes and the regulation of root hair expansin genes in a comparative approach.

• Korean Journal of Microbiology
• /
• v.35 no.2
• /
• pp.169-172
• /
• 1999

Small-seeded legumes can be cultured enclosed in slant agar tubes if dlese plants are to he used for authenicaiing rhizobia or for enumerating 1-hizobia by the plant-inlection technique. An improved method has been developed with substiluting agar slant lor Korean paper(Har7ji). This method was panicularly useful for legumes with rigid radicle such as Cn.xsin 1mnmame. With this method Bmr!,~li1rzobin,17 sp. stram CN9135 on C nonmne induced root nodules biginning at day 7 of the nodulation period in 6% of the l ~ l a ~ l s , and all of ihe plants nodulated 14 days after inoculation by strain CN9135.

• Molecules and Cells
• /
• v.27 no.2
• /
• pp.129-134
• /
• 2009

Legume plants develop root nodules to recruit nitrogen-fixing bacteria called rhizobia. This symbiotic relationship allows the host plants to grow even under nitrogen limiting environment. Since nodule development is an energetically expensive process, the number of nodules should be tightly controlled by the host plants. For this purpose, legume plants utilize a long-distance signaling known as autoregulation of nodulation (AON). AON signaling in legumes has been extensively studied over decades but the underlying molecular mechanism had been largely unclear until recently. With the advent of the model legumes, L. japonicus and M. truncatula, we have been seeing a great progress including isolation of the AON-associated receptor kinase. Here, we summarize recent studies on AON and discuss an updated view of the long-distance control of nodulation.

• Korean Journal of Microbiology
• /
• v.49 no.2
• /
• pp.131-136
• /
• 2013

This study was conducted to select rhizobia from hairy vetch (Vicia villosa Roth) with nodulation and excellent nitrogen-fixing ability. Hairy vetch root was collected from 7 of cultivation region of all over the country, rhizobia were isolated from the root nodules. Isolates were re-inoculated into a hairy vetch separately and studied nodulation and nitrogen-fixing ability. As a result, total of 52 Rhizobium isolates were isolated from the hairy vetch root nodules, among these, 16 isolates were Rhizobium which show good growth at more than 0.5% NaCl concentration. These 16 isolates were re-inoculated separately, 8 weeks after, good root nodule formation was observed from Rhizobium sp. RH1, RH3, RH81, RH82, RH84, and RH93 strain treated samples. Six isolates were positive for nitrogen fixing ability, the highest acetylene reduction activity was shown by Rhizobium sp. RH84. Results suggest that the Rhizobium sp. RH84 could be used as the possibility of its application as a green manure crop of hairy vetches in nonuniform salt distribution reclaimed land.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.6 no.3
• /
• pp.151-156
• /
• 1986

There are differences in recommendations in the USA as to whether nitrogen fertilizer should be applied when establishing alfalfa (Medicago sativa L). The reason for not applying nitrogen is because some researchers found the addition of nitrogen reduced nodulation of alfalfa plants. A replicated experiment was conducted under controlled environmental conditions at the University of Nevada-Reno, Reno, Nevada, USA, to determine the effects of nitrogen application on seedling growth and nodulation of alfalfa when grown in a cool environment. A sterile sand was used in the growing media to which a complete nutrient solution minus nitrogen was applied volumetrically to each pot daily. Half of the pots received $NH_4NO_3$, at the rate of 11.2 kg/ha, at seeding and two and four weeks after planting, giving a total nitrogen application rate of 33.6 kg/ha. Rhizobia inoculant (R-12) consisted of a mixture of strains 171-15a. 1682c and 80 PI 265 of Rhizobium meliloti. Inoculant was applied to the seeds prior to planting and to the sand media at two and four weeks after seeding. Twenty seeds were planted in pots 14.0 cm in diameter and 11.5 cm deep. Seedlings were thinned after emergence to ten plants per pot. They were grown in a controlled environment chamber with a 16-hour light period. Soil temperatures at 6 cm depth ranged from $5.7^{\circ}C\;to\;21.5^{\circ}C$ and had a daily mean of $16.2^{\circ}C$ Plants were harvested at weekly intervals for seven weeks at which time root, shoot and total length, dry weight, volume and number of nodules per plant were determined. Root, shoot and total length were not affected by nitrogen fertilizer. However, application of nitrogen increased the size of the seedlings as determined by dry weight and volume when compared to plants which were not fertilized. This indicates that rhizobia did not fix enough atmospheric nitrogen to promote good growth. Nitrogen application resulted in significantly more nodules per plant. The effect of nitrogen fertilizer became more apparent as the plant became older. Results of this experiment show there are benefits from applying nitrogen at a low rate when establishing alfalfa under a cool environment.

• The Plant Pathology Journal
• /
• v.15 no.2
• /
• pp.127-130
• /
• 1999

Cytological changes of cowpea root at the early stage of root nodule formation (within 5 days after inoculation) were viewed by light and electron microscopy. The root region affected by the rhizobial infection, which was composed of a redial array of cortical cells, had prominent cell divisions, mostly anticlinal in the inner cortical cells and in addition oblique and periclinal in the outer cells. An infected root hair cell (or root hair-producing epidermal cell) had numerous infection threads and degenerated cytoplasm. Module meristem was formed adjacent to the infected root hair cell, and characterized by dense cytoplasm, prominent nucleus, numerous small vacuoles, and increased plastids, containing infection threads as well. Bacterial cells were dividing inside the infection thread, the wall materials of which appeared to be dissolved ad accumulated in small vacuoles. inner cortical cells contiguous to the nodule meristem appeared to be actively dividing and dedifferentiating; however, they were not infected by the rhizobia. These structural characteristics are similar to those in the Bradyrhizobium-soybean association previously reported, and may reflect the similar cytological process in cowpea in the early nodule formation.

• Korean Journal of Microbiology
• /
• v.24 no.2
• /
• pp.98-105
• /
• 1986

Rhizobium meliloti 102 F 51, the symbiotic partner of alfalfa, was mutagenized with N-methyl-N'-nitro-N-nitrosoguanidine (NTG) and UV-irradiation. Three group of mutants which form white, white-pink and red nodules were selected. The adetylene reduction activity, nodulation activity, amount of heme synthesis during the nodulation, and ${\delta}-aminolevulinic$ acid synthetase (ALAS) and ${\delta}-aminolevulinic$ acid dehydratase (ALAD) activities in free living rhizobia and bacteroid states of the each group of mutants were compared. The mutants forming white nodules showed lower acetylene reduction activity compared to those of red nodule forming mutants. The two key enzymes for the heme synthetic pathway, ALAS and ALAD activities of the mutants forming red nodules was much higher than those of the mutants forming white nodules in bacteroid state, however no significant difference was observed in free living state. In the nodules the ALAS was detected only in bacteroid fraction, while ALAD was detected both in bacteroid and plant fraction. ALAS was dramatically increased with the heme synthesis during the nodulation, while ALAD was decreased in plant fraction but slight increase was observed in bacteroid fraction.