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Omics are the most promising approaches to investigate microbes for which no genetic tools exist such as the nitrogen-fixing symbiotic Frankia. A proteogenomic analysis of symbiotic Frankia alni was done by comparing those proteins more and less abundant in Alnus glutinosa nodules relative to N2-fixing pure cultures with propionate as the carbon source. There were 250 proteins that were significantly overabundant in nodules at a fold change (FC) ≥ 2 threshold, and 1429 with the same characteristics in in vitro nitrogen-fixing pure culture. Nitrogenase, SuF (Fe–Su biogenesis) and hopanoid lipids synthesis determinants were the most overabundant proteins in symbiosis. Nitrogenase was found to constitute 3% of all Frankia proteins in nodules. Sod (superoxide dismutase) was overabundant, indicating a continued oxidative stress, while Kats (catalase) were not. Several transporters were overabundant including one for dicarboxylates and one for branched amino acids. The present results confirm the centrality of nitrogenase in the actinorhizal symbiosis. [ABSTRACT FROM AUTHOR]

None of the known native actinorhizal species in Turkey, Alnus glutinosa and A. orientalis (Betulaceae), Datisca cannabina (Datiscaceae), Elaeagnus angustifolia and Hippophae rhamnoides (Elaeagnaceae), and the widely-planted exotic Casuarina cunninghamiana (Casuarinaceae), have confirmed records of actinorhizae in Turkey. This study determined the capacity of representative actinorhizal plants in Turkey to form nodules, cluster roots and ectomycorrhizal roots in a typical central Anatolian soil with and without amendment of soil and nodule extracts, as well as in soil from Adana and Izmir. Nodulation was confirmed experimentally for E. angustifolia and C. cunninghamiana in Niğde soil (the latter only with addition Adana or Izmir soil), but only observationally for A. glutinosa during sample collection in Rize. Cluster roots developed strongly in C. cunninghamiana, and likewise ectomycorrhizal roots in Allocasuarina verticillata (included as a reference species) but only to a lesser extent in C. cunninghamiana. The nodulation status of the natives, D. cannabina and H. rhamnoides, remains to be investigated. [ABSTRACT FROM AUTHOR]

Omics are the most promising approaches to investigate microbes for which no genetic tools exist such as the nitrogen-fixing symbiotic Frankia. A proteogenomic analysis of symbiotic Frankia alni was done by comparing those proteins more and less abundant in Alnus glutinosa nodules relative to N-replete pure cultures with propionate as the carbon source and ammonium as the nitrogen-source. There were 250 proteins that were significantly overabundant in nodules at a fold change (FC) ≥ 2 threshold, and 1429 with the same characteristics in in vitro nitrogen-replete pure culture. Nitrogenase, SuF (Fe–Su biogenesis) and hopanoid lipids synthesis determinants were the most overabundant proteins in symbiosis. Nitrogenase was found to constitute 3% of all Frankia proteins in nodules. Sod (superoxide dismutase) was overabundant, indicating a continued oxidative stress, while Kats (catalase) were not. Several transporters were overabundant including one for dicarboxylates and one for branched amino acids. The present results confirm the centrality of nitrogenase in the actinorhizal symbiosis.

We have analysed the growth and symbiotic performance of actinorhizal Discaria trinervis at various Ca supply regimes. We aimed at discriminating between specific, if any, effects on nodulation and general growth stimulation by Ca. The hypothesis that a high Ca supply would interfere with nodulation by Frankia was also tested. Results showed that plant growth increased with Ca supply. Nodulation was stimulated by moderate levels of Ca, but inhibited by Ca higher than 0.77 mM. Growth of nodules was less affected by Ca than shoot and root growth. Ca concentration of symbiotic plants increased with Ca supply, but nitrogen concentration was independent of Ca at concentrations which did not impair plant growth. All together, these results show that Ca has a positive effect on the establishment and functioning of the symbiosis between Discaria trinervis and Frankia. However, the positive influence of Ca was more likely due to a promotion of plant growth rather than a direct effect on nodule growth and nitrogen fixation itself. At high levels of Ca supply nodulation was impaired. Given the intercellular infection pathway in Discaria trinervis, we suggest that the increment of Ca availability would strengthen its root cell walls, thus decreasing Frankia penetration of the root. [ABSTRACT FROM AUTHOR]

In red alder (Alnus rubra Bong.) the nitrogen fixing actinomycete Frankia can be divided into strains which form spores (sp+) within nodules and those that do not. Red alder nodules were collect from 42 sites in southwestern British Columbia and their spore type was determined. Sp+ nodules were found in 18 of the sites, where their proportion ranged from 4 to 93%. The distribution of sites with sp+ nodules was clumped, with significant autocorrelation at the 0–10 km interval. No sp+ nodules were found in any of the eight stands in the submaritime region, indicating a possible continentality effect on spore type distribution. There was a significant positive association between the presence of Rubus spectabilis and the presence sp+ nodules. Stand and soil chemical variables were generally poor predictors of the proportion of sp+ nodules, although total soil nitrogen and exchangeable phosphorus accounted for 36.4 and 28.5% respectively, of the variation in the proportion of sp+ nodules on sites where they were present. There was also a small but significant negative relation between soil pH and the proportion of sp+ nodules and young stands generally did not have any sp+ nodules. [ABSTRACT FROM AUTHOR]

Inoculation trials were set up in fumigated nursery beds for red alder ( Alnus rubra Bong.) bare-root seedling production. Frankia inoculum was applied either as nodule homogenate or as pure culture (strain ArI5). The plots were laid out in 4 blocks of 8 treatments consisting of: control, nodule suspension, and three levels each of cell suspension and cells applied with a peat carrier. Numbers, height, and percentage nodulation on the seedlings were determined at mid-season. Numbers, size, dry weights, and degree of nodulation were determined at lifting. The peat inoculum treatment produced larger seedlings than the other treatments, both at mid-season and at lifting. The other treatments had little effect on growth. Size differences paralleled differences in degree of nodulation. Differences in percentage of seedlings nodulated were most pronounced at midseason, indicating that inoculation confered primarily an early-season advantage. [ABSTRACT FROM AUTHOR]

To determine if inoculation increases nodulation and yield of bare-root red alder ( Alnus rubra Bong.), fumigated nursery plots were treated with inoculum and ammonium sulfate (28 kg N ha) in a factorial experiment. Inoculum was alder soil with 100 infective units of Frankia g. Seedlings were evaluated for nodulation at age 10 wk and when lifted, at age 9 mo. Inoculation produced earlier and more extensive nodulation and increased seedling root collar diameter, height, and dry weight. Fertilization decreased seedling height, but did not decrease nodulation. No interaction of fertilization with inoculation was found. Inoculated unfertilized plots had the highest yield of packable seedlings (257 m), and uninoculated fertilized seedlings had the lowest yield (126 m). [ABSTRACT FROM AUTHOR]

A morphological analysis of the initiation and development of root nodules of Elaeagnus angustifolia and Myrica cerifera inoculated with pure-cultured Frankia strains DDB 011610 or DDB 020110 was undertaken. From ultrastructural observations it was determined that both of these Frankia strains can infect Elaeagnus by an intercellular penetration mechanism and Myrica by the root hair infection mechanism. This indicates that both of these strains have the ability to infect host plant roots by either of two mechanisms. The reverse, that Elaeagnus or Myrica could be infected by both mechanisms, was not observed. The infection and nodule development processes of these two plants in combination with these strains were similar to observations made in previous studies ( Miller and Baker 1985, Torrey and Callaham 1979). However, one exception was identified in the development of the prenodule of Myrica when infected with strain 011610, in that endophytic hyphae developed vesicles within the cells of the prenodule. This event has not been described before for any of the actinorhizal genera and may be an indication of less than optimal compatibility between the host plant and the symbiont. [ABSTRACT FROM AUTHOR]