Lysis of bacterioids in the vicinity of the host cell nucleus in an ineffective (fix-) root nodule of soybean (Glycine max)

Werner, Dietrich; Mörschel, Erhard; Kort, Renate; Mellor, Robert B.; Bassarab, Stefan

doi:10.1007/bf00397414

Cited by 45 publications

(15 citation statements)

References 28 publications

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“…This suggests that NH 4 ϩ is not a signal for nodule organogenesis and that younger BTs release NH 4 ϩ by a mechanism not involving nitrogenase action, such as the utilization of amino acids as a C source (see below). Instead, if these plants are infected with a nifA mutant strain, SBs are degraded at an early stage (25,58,209). This indicates that the nifA regulatory gene, as in the case of elongated nodules, is required for SB maintenance, while nifH, and thus nitrogenase activity, is not (60,129).…”

Section: Nhmentioning

confidence: 99%

Key Role of Bacterial NH ₄ ⁺ Metabolism in Rhizobium-Plant Symbiosis

Patriarca

Tatè

Iaccarino

2002

Microbiol Mol Biol Rev

157

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Symbiotic nitrogen fixation is carried out in specialized organs, the nodules, whose formation is induced on leguminous host plants by bacteria belonging to the family Rhizobiaceae. Nodule development is a complex multistep process, which requires continued interaction between the two partners and thus the exchange of different signals and metabolites. NH4+ is not only the primary product but also the main regulator of the symbiosis: either as ammonium and after conversion into organic compounds, it regulates most stages of the interaction, from the production of nodule inducers to the growth, function, and maintenance of nodules. This review examines the adaptation of bacterial NH4+ metabolism to the variable environment generated by the plant, which actively controls and restricts bacterial growth by affecting oxygen and nutrient availability, thereby allowing a proficient interaction and at the same time preventing parasitic invasion. We describe the regulatory circuitry responsible for the downregulation of bacterial genes involved in NH4+ assimilation occurring early during nodule invasion. This is a key and necessary step for the differentiation of N2-fixing bacteroids (the endocellular symbiotic form of rhizobia) and for the development of efficient nodules

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Section: Nhmentioning

confidence: 99%

Key Role of Bacterial NH ₄ ⁺ Metabolism in Rhizobium-Plant Symbiosis

Patriarca

Tatè

Iaccarino

2002

Microbiol Mol Biol Rev

157

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“…Further studies will be conducted to understand the biological significance of this protease inhibitor within nodules induced by Rhizobium mutants producing Fix-phenotypes, such as those that are characterized by lysis of bacteroids (early senescence) (Werner et al, 1984). Purification and complete characterization of the specific protease inhibited by the nodule inhibitor will also be undertaken.…”

Section: Lnvolvement Of the Nodule Protease Lnhibitor In Nodule Senesmentioning

confidence: 99%

A nodulin specifically expressed in senescent nodules of winged bean is a protease inhibitor.

et al. 1991

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Nodule senescence is one aspect of nitrogen fixation that is important to study from the perspective of improving the host-bacteroid interaction. In winged bean nodules, a 21-kilodalton protein is specifically expressed when senescence begins. Using subcellular fractionation, we observed that this plant protein interacts with the bacteroids. Microsequencing of the protein allowed us to obtain a specific oligonucleotide that was used to isolate the corresponding nodule cDNA. Sequence analysis of this cDNA revealed that the 21-kilodalton protein has all of the features of a legume Kunitz protease inhibitor. Subsequent analysis confirmed that this nodulin is indeed a protease inhibitor. lmmunocytochemical study showed that the protease inhibitor is exclusively localized i11 infected senescent cells of the nodule, particularly in disorganized bacteroids, the peribacteroid membrane, vacuole membranes, and in the vacuole fluid. The specific expression of a protease inhibitor at senescence may be of particular interest if the targeted proteolytic activity is important for the symbiotic relationship. This point is discussed in relation to the known nodule proteases.

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“…(Dudman, 1977;Dunn and Karr, 1992), another possible role for NPS would be protection or nutrition of bacteroids during nodule senescence and disintegration; this was the working hypothesis for the work reported here. Micrographs of senescing nodules do indicate lysis of bacteroids prior to complete destruction of infected cells (Kijne, 1975;Paau et al, 1980;Werner et al, 1984;Pladys and Rigaud, 1988). Because the host cytoplasm in nodules contains a variety of proteolytic enzymes (Malik et al, 1981;Pfeiffer et al, 1983;Pladys et al, 1986), bacteroids may come under attack by host proteases.…”

mentioning

confidence: 99%

Fate of Nodule-Specific Polysaccharide Produced by Bradyrhizobium japonicum Bacteroids

Streeter

Peters²,

Salminen³

et al. 1995

Plant Physiol.

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A polysaccharide produced by 5radyrhizobium japonicum bacteroids i n nodules (NPS) on soybean (Glycine max [LI Merr.) roots is different in composition and structure from the extracellular polysaccharide produced in culture by this organism. lsogenic strains either capable or incapable of NPS synthesis supported similar rates of plant growth and nitrogenase activity, indicating that polysaccharide deposition was not detrimental. The possibility that NPS may have some protective or nutritional role for bacteroids was considered. Analysis of disintegrating nodules over periods of 1 to 3 months indicated greater recovery of viable bacteria from NPS+ nodules prior t o the breakdown of NPS. During and after the breakdown of NPS, the decline in viable bacteria was similar for NPS+ and NPS-strains. Bacteroid destruction in senescing nodules may be accelerated by exposure t o proteolytic enzymes in host cytoplasm; however, highly purified NPS had no significant effect on the i n vitro activity of partially purified proteases, so protection of bacteroids via this mechanism is unlikely. 5. japonicum USDA 438 did not utilize NPS as a carbon source for growth in liquid culture. I n vitro assays of NPS depolymerase activity in cultured bacteria and bacteroids were negative using a variety of strains, all of which contained extracellular polysaccharide depolymerase. It seems highly unlikely that 5. japonicum can utilize the polysaccharide it synthesizes in nodules, and NPS breakdown in senescing nodules is probably caused by saprophytic fungi.Certain strains of Bradyrkizobium japonicum and Bradyrkizobium elkanii (formerly B. japonicum Group 11; Kuykendall et al., 1992) synthesize large quantities of polysaccharide in soybean nodules . The NPS accumulates in the symbiosomes of infected cells and is a major feature seen in micrographs of infected cells of soybean nodules after 50 or 60 d of growth

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Lysis of bacterioids in the vicinity of the host cell nucleus in an ineffective (fix-) root nodule of soybean (Glycine max)

Cited by 45 publications

References 28 publications

Key Role of Bacterial NH ₄ ⁺ Metabolism in Rhizobium-Plant Symbiosis

Key Role of Bacterial NH ₄ ⁺ Metabolism in Rhizobium-Plant Symbiosis

A nodulin specifically expressed in senescent nodules of winged bean is a protease inhibitor.

Fate of Nodule-Specific Polysaccharide Produced by Bradyrhizobium japonicum Bacteroids

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Lysis of bacterioids in the vicinity of the host cell nucleus in an ineffective (fix-) root nodule of soybean (Glycine max)

Cited by 45 publications

References 28 publications

Key Role of Bacterial NH 4 + Metabolism in Rhizobium-Plant Symbiosis

Key Role of Bacterial NH 4 + Metabolism in Rhizobium-Plant Symbiosis

A nodulin specifically expressed in senescent nodules of winged bean is a protease inhibitor.

Fate of Nodule-Specific Polysaccharide Produced by Bradyrhizobium japonicum Bacteroids

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Key Role of Bacterial NH ₄ ⁺ Metabolism in Rhizobium-Plant Symbiosis

Key Role of Bacterial NH ₄ ⁺ Metabolism in Rhizobium-Plant Symbiosis