A simple model based on known plant defence reactions is sufficient to explain most aspects of nodulation

Mellor, Robert B.; Collinge, David B.

doi:10.1093/jxb/46.1.1-a

Cited by 41 publications

(23 citation statements)

References 87 publications

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“…These hypotheses regarding the relationship of the sweetclover sym genes to the two-receptor model of Ardourel et al (1994) could be tested in part by construction of double mutants, such as a sym-4/sym-5 mutant, in which an additive phenotype (Had+ and non-nodulating) would support the model, and an epistatic effect would suggest a single signal transduction pathway. We are also investigating the hypothesis that a defense response occurs in the sweetclover mutants after inoculation with R. meliloti, as elaborated in the model recently proposed by Mellor and Collinge (1995).…”

Section: Discussionmentioning

confidence: 99%

The Auxin Transport Inhibitor N-(1-Naphthyl)phthalamic Acid Elicits Pseudonodules on Nonnodulating Mutants of White Sweetclover

Dickstein

Cary

et al. 1996

Plant Physiol.

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The collection of symbiotic (sym) mutants of white sweetclover (Melilotus alba Desr.) provides a developmental sequence of mutants blocked early in infection or nodule organogenesis. Mutant phenotypes include non-nodulating mutants that exhibit root-hair deformations in response to Rhizobium meliloti, mutants that form ineffective nodules lacking infection threads, and mutants that form infection threads and ineffective nodules. Mutant alleles from both the sym-1 and the sym-3 loci exhibited a non-nodulating phenotype in response to R. meliloti, although one allele in the sym-1 locus formed ineffective nodules at a low frequency. Spot-inoculation experiments on a non-nodulating allele in the sym-3 locus indicated that this mutant lacked cortical cell divisions following inoculation with R. meliloti. The auxin transport inhibitor K ( 1 -naphthyl)phthalamic acid elicited development of pseudonodules at a high frequency on all of the sweetclover sym mutants, including the nonnodulating mutants, in which the early nodulin ENODZ was expressed. This suggests that K ( 1 -naphthyl)phthalamic acid activates cortical cell divisions by circumventing a secondary signal transduction event that is lacking in the non-nodulating sweetclover mutants. The sym-3 locus and possibly the sym-1 locus appear to be essential to early host plant responses essential to nodule organogenesis.

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Section: Discussionmentioning

confidence: 99%

The Auxin Transport Inhibitor N-(1-Naphthyl)phthalamic Acid Elicits Pseudonodules on Nonnodulating Mutants of White Sweetclover

Dickstein

Cary

et al. 1996

Plant Physiol.

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“…Regarding root nodulation by rhizobial infection, it is evident that plant factors are crucial in determining the number of nodules on the root through long-distance signaling (13,29,95,107,117,128,170). The interesting physiological response by which leguminous plants maintain their optimal symbiotic association with rhizobia is called autoregulation (a self-regulating mechanism) (14,122).…”

Section: Discussionmentioning

confidence: 99%

Biogenic Amines in Rhizobia and Legume Root Nodules

Fujihara

2009

Microb. Environ.

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Root-nodule bacteria (rhizobia) are of great importance for nitrogen acquisition through symbiotic nitrogen fixation in a wide variety of leguminous plants. These bacteria differ from most other soil microorganisms by taking dual forms, i.e. a free-living form in soils and a symbiotic form inside of host legumes. Therefore, they should have a versatile strategy for survival, whether inhabiting soils or root nodules formed through rhizobia-legume interactions. Rhizobia generally contain large amounts of the biogenic amine homospermidine, an analog of spermidine which is an essential cellular component in most living systems. The external pH, salinity and a rapid change in osmolarity are thought to be significant environmental factors affecting the persistence of rhizobia. The present review describes the regulation of homospermidine biosynthesis in response to environmental stress and its possible functional role in rhizobia. Legume root nodules, an alternative habitat of rhizobia, usually contain a variety of biogenic amines besides homospermidine and the occurrence of some of these amines is closely associated with rhizobial infections. In the second half of this review, novel biogenic amines found in certain legume root nodules and the mechanism of their synthesis involving cooperation between the rhizobia and host legume cells are also described.

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“…Genes categorized under defense and secondary metabolism functions should also be appropriate targets of study given the possible involvement, or suppression, of host defenses during infection by Rhizobium (Hirsch and Fang, 1994;Mellor and Collinge, 1995;Spaink, 1995). In particular, an endochitinase homolog may be intriguing to examine (EST 00194; serial nos.…”

Section: Genes Of Interestmentioning

confidence: 99%

Expressed Sequence Tags from a Root-Hair-Enriched Medicago truncatula cDNA Library1

Covitz¹,

Smith

Long

1998

Plant Physiology

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The root hair is a specialized cell type involved in water and nutrient uptake in plants. In legumes the root hair is also the primary site of recognition and infection by symbiotic nitrogenfixing Rhizobium bacteria. We have studied the root hairs of Medicago truncatula, which is emerging as an increasingly important model legume for studies of symbiotic nodulation. However, only 27 genes from M. truncatula were represented in GenBank/EMBL as of October, 1997. We report here the construction of a root-hairenriched cDNA library and single-pass sequencing of randomly selected clones. Expressed sequence tags (899 total, 603 of which have homology to known genes) were generated and made available on the Internet. We believe that the database and the associated DNA materials will provide a useful resource to the community of scientists studying the biology of roots, root tips, root hairs, and nodulation.

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A simple model based on known plant defence reactions is sufficient to explain most aspects of nodulation

Cited by 41 publications

References 87 publications

The Auxin Transport Inhibitor N-(1-Naphthyl)phthalamic Acid Elicits Pseudonodules on Nonnodulating Mutants of White Sweetclover

The Auxin Transport Inhibitor N-(1-Naphthyl)phthalamic Acid Elicits Pseudonodules on Nonnodulating Mutants of White Sweetclover

Biogenic Amines in Rhizobia and Legume Root Nodules

Expressed Sequence Tags from a Root-Hair-Enriched Medicago truncatula cDNA Library1

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