| Mutant Symbol | C90 |
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| Allele Symbol | nip |
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| Gene and Mutation Location | NIP |
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| Symbiotic Phenotype Brief | Inf+Bar-Bad-Nod+Fix- |
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| Phenotype Detail | The mutant failed to form pink nitrogen-fixing nodules that occur in the wild-type symbiosis, but instead developed small bump-like nodules on its roots that were blocked at an early stage of development. The mutant plants showed an approximate 2-fold increase in nodule number as compared to wild-type plants. Examination of the nip nodules by light microscopy after staining with X-Gal for S. meliloti expressing a constitutive GUS gene, by confocal microscopy following staining with SYTO-13, and by electron microscopy revealed that nip initiated symbiotic interactions and formed nodule primordia and infection threads. The infection threads in nip proliferated abnormally and very rarely deposited rhizobia into plant host cells; rhizobia failed to differentiate further in these cases. nip nodules contained autofluorescent cells and accumulated a brown pigment. Histochemical staining of nip nodules revealed this pigment to be polyphenolic accumulation. RNA blot analyses demonstrated that nip nodules expressed only a subset of genes associated with nodule organogenesis, as well as elevated expression of a host defense-associated phenylalanine ammonia lyase gene. Nodule-specific marker genes for nodule primodia (ENOD40) and infection thread formation (MtN12) were expressed in nodulating nip root systems. Genes that are associated with nodule organogenesis
(ENOD2, ENOD8) were not. nip plants were observed to have abnormal lateral roots. nip plant root growth and nodulation responded normally to ethylene inhibitors and precursors. |
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| Single gene targeted? | yes |
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| Extra Information | Based on developmental phenotypes, Veereshlingam et al. proposed that the NIP gene acts after LIN and before MtSYM1 and the DNF genes. |
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| Mutagenesis Method | EMS |
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| Mutant Class | Nod+Fix- |
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| Allelism | not allelic to lin, rit, bit, TE7 (Mtsym1), dnf1, dnf2, dnf3, dnf4, dnf5, dnf6, or dnf; nip did not complement latd |
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| The earliest development stage known to be affected | Bacteroid release |
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| Wildtype Line | Jemalong A17 |
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| External Link | http://www.genome.clemson.edu/affiliated_cugi/medicago/genelist.html |
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