A Transmissible Plant Shoot Factor Promotes Uptake Hydrogenase Activity in <i>Rhizobium</i> Symbionts

Bedmar, Eulogio J.; Phillips, Donald A.

doi:10.1104/pp.75.3.629

Cited by 27 publications

(9 citation statements)

References 21 publications

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“…The hydrogen produced as a by‐product of N 2 fixation in the legume crop may enhance the fertility of the soil and improve the growth and yield of the subsequent crop. This plant growth promotion would also help to address evolutionary questions concerning why HUP– symbioses have thrived compared with the more energetically efficient HUP+ symbioses, and why at least some legume plants have an ability to regulate the expression of the HUP genes within their symbiotic rhizobia (Bedmar & Phillips 1984). Although the mechanism by which H 2 fertilization of soils enhances plant growth has yet to be revealed, the most likely explanation involves the enhanced growth of H 2 ‐oxidizing micro‐organisms in the soil.…”

Section: Discussionmentioning

confidence: 99%

Hydrogen fertilization of soils – is this a benefit of legumes in rotation?

Dong

Kettlewell

et al. 2003

Plant Cell & Environment

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Hydrogen gas (H 2 ) is an obligate byproduct of the N 2 -fixing enzyme, nitrogenase, claiming about 5-6% of the crops' net photosynthesis but most, if not all of the H 2 lost from nodules is oxidized by the soil surrounding the root system of the plant. When soils not recently used to support the growth of legumes were exposed to H 2 gas at a rate and duration similar to that of soil adjacent to legume nodules, the fertility of the soil was enhanced in comparison with soil treated with air. Under growth-chamber and field conditions, H 2 -treated soils improved the growth performance of spring wheat, canola, barley and soybean (nonsymbiotic) when compared with untreated soils or with soils pretreated with air. The dry weights of 4-to 7-weekold plants were 15-48% greater in the H 2 -treated soil, and in barley and spring wheat, tiller number of 7-week-old plants were 36 and 48% greater in the H 2 -treated soils. These findings may contribute to an explanation for the persistence of H 2 evolving associations in agricultural legume symbioses selected for high yields (Uratsu et al ., Crop Science 22, 600-602, 1982) and suggest that it may be possible to isolate, identify and culture the micro-organisms that are responsible for at least some of the benefits of legumes in crop rotation.

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Section: Discussionmentioning

confidence: 99%

Hydrogen fertilization of soils – is this a benefit of legumes in rotation?

Dong

Kettlewell

et al. 2003

Plant Cell & Environment

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“…The host plant control affect can even be specific to the particular host cultivar. For example, the pea cultivar Feltham First causes R. leguminosarum strain 128C53 to be Hup-, whereas on other cultivars that strain is Hup+ (Bedmar and Phillips, 1984).…”

Section: Host-regulated Hup Expressionmentioning

confidence: 98%

Toward More Productive, Efficient, and Competitive Nitrogen-Fixing Symbiotic Bacteria

Maier

Triplett

1996

Critical Reviews in Plant Sciences

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The prospects of developing strains of legume nodule bacteria that provide higher productivity of leguminous plants are described. The generic, biochemical, physiological, regulatory, and economic constraints that govern the ability of private and public efforts to construct better inoculants for legume nodulation are discussed. Success in constructing better inoculants requires a two-pronged approach. First, strains need to be improved in order to compete successfully with indigenous strains for root nodulation of legumes. Several loci have been identified to date that affect competitiveness for strain nodule occupancy. Usually mutations in these loci affect the ability of a strain to form nodules rapidly and efficiently. Other loci, such as those that confer antibiotic production, can be added to strains to enhance nodulation competitiveness when co-inoculated with antibiotic-sensitive strains. Second, the inoculum strains must be improved with respect to symbiotic nitrogen fixation. Efforts to enhance the symbiotic productivity of legume nodule bacteria either by mutation or genetic engineering are also described. The best characterized example of these is the hydrogenase system. Due to nitrogenase-dependent catalysis of proton reduction, diazotrophs evolve large amounts of H,. An approach to maximize the efficiency of symbiotic N, fixation, and therefore of legume productivity, is to construct strains of Rhizobium with the ability to oxidize this otherwise wasted H,. The electrons produced by H, oxidation are funneled through energy-conserving electron transport chains. Our knowledge of the genetics and biochemistry of H, oxidation in Bradyrhizobium japonicum and Rhizobium leguminosarum has developed rapidly in recent years. At least 20 genes are needed for these bacteria to manufacture and efficiently express a nickel-containing H,-uptake hydrogenase. These genes include those encoding regulatory elements, posttranslational processing enzymes, nickel-sensing and nickel-metabolism proteins, and electron transport components for integrating the electrons from H, oxidation into the respiratory chain. Some of the components for oxidizing H, in the symbiotic N, fixing bacteria are distinct from the analogous components in (nonsymbiotic) H, oxidizing bacteria.

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“…It is interesting to note that the expression of the bacterial Hup system appears to be plant dependent." 3 - 114 Evans et al" 5 have discussed the properties and function of Hup in detail, and readers who wish to pursue this topic further are advised to read that paper.…”

Section: E Bioenergetics Of N 2 Fixationmentioning

confidence: 98%