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since 4/20/2004

Last updated 10/01/09

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Mutant Detail


Mutant Detail:
Mutant SymbolTR25 
Allele Symboldmi2-1 
Gene and Mutation LocationDMI2 (NORK) (Single nucleotide (T) deletion causing frame shift and early translational termination in the extracellular domain) 
Symbiotic Phenotype BriefCalcium flux+, Calcium spiking-, Has+, Hab-(touch response), Hab+(no touch response), Enod gene expression-, Ccd-, Hac-(touch response), Hac+(no touch response), Inf-, Nod-, Myc+- 
Phenotype DetailNod-; defective in calcium spiking; with induced touch response, the mutant showed root hair tip swelling (Has) but blocked for branching (Hab-), no root curling (Hac-) in response to live bacteria, lack cortical cell division; blocked in the induction of ENOD11 and ENOD40; dramatically reduced induction of RIP1; Recessive; A more recent paper by Esseling et al., 2004 showed that when care is taken not to induce touch response, the mutant root hairs respond morphologically like the wild type to nod factor. Root hairs are more sensitive to medium refreshment than wild-type root hairs, and they still have the property to reorient their growth axis when challenged with NF (Nod factor), which is a prerequisite for root hair curling. Multifaceted three dimensional curls in which bacteria were entrapped, as well as infection threads, were absent in dmi2-1 root hairs (Inf-). Root hairs make two-dimensional 180 curls but do not entrap bacteria in a three-dimensional pocket because curling stops when the root hair tip touches its own shank. According to Morandi et al. 2004 paper, TR25 belongs to mycorrhizal phenotype 3 (Myc+-). Phenotype 3 showed typical thick lens-shaped appressoria with no intercellular hyphae developing from them and normal appressoria leading to the formation of arbuscules on the same root system. For all the mutants belonging to mycorrhizal phenotype 3, the mycorrhizal fungus G. intraradices forms significantly much more typical AM structures than G. mosseae. 
Single gene targeted?yes 
Extra InformationThe mutant showed no measurable transcriptional changes in response to S. meliloti inoculation. It is mutated in the nodulation receptor-like kinase, NORK. A recent paper by Esseling et al., 2004 showed that when care is taken not to induce touch response, the mutant root hairs respond morphologically like the wild type to nod factor. TR25 was previously described as Myc- (Catoira et al. 2000), Morandi et al. 2004 observed a Myc+- phenotype. This different result may be attributed to (1) the use of a very "efficient" inoculum in this new experiment, especially G. intraradices, which gives a very rapid and intense colonisation thus facilitating visualisation of arbuscules, (2) the fact that, in previous observations, the "search image" was different, since the concept of [Myc-/+] had not been defined. 
Mutagenesis Methodgamma rays 
Mutant ClassNod- 
Allelismnot allelic to dmi1, dmi3 or nsp1, determined by complementation test 
The earliest development stage known to be affectedCalcium spiking 
Wildtype LineJemalong J5 
External Linkhttp://www.genome.clemson.edu/affiliated_cugi/medicago/genelist.html 

References:
Authors Year Title Locator
Ane JM, Levy J, Thoquet P, Kulikova O, de Billy F, Penmetsa V, Kim DJ, Debelle F, Rosenberg C, Cook DR, Bisseling T, Huguet T and Denarie J 2002 Genetic and cytogenetic mapping of DMI1, DMI2, and DMI3 genes of Medicago truncatula involved in Nod factor transduction, nodulation, and mycorrhization Mol Plant Microbe Interact. 15(11):1108-18 
Catoira R, Galera C, de Billy F, Penmetsa RV, Journet EP, Maillet F, Rosenberg C, Cook D, Gough C and Denarie J 2000 Four genes of Medicago truncatula controlling components of a nod factor transduction pathway Plant Cell. 12(9):1647-66 
Endre G, Kereszt A, Kevei Z, Mihacea S, Kalo P and Kiss GB 2002 A receptor kinase gene regulating symbiotic nodule development Nature. 417(6892):962-6 
Esseling JJ, Lhuissier FG and Emons AM 2004 A nonsymbiotic root hair tip growth phenotype in NORK-mutated legumes: implications for nodulation factor-induced signaling and formation of a multifaceted root hair pocket for bacteria Plant Cell. 16(4):933-44 
Mitra RM, Shaw SL and Long SR 2004 Six nonnodulating plant mutants defective for Nod factor-induced transcriptional changes associated with the legume-rhizobia symbiosis Proc Natl Acad Sci U S A. 101(27):10217-22 
Morandi D, Prado E, Sagan M, and Duc G 2004 Characterisation of new symbiotic Medicago truncatula (Gaertn.) mutants, and phenotypic or genotypic complementary information on previously described mutants. Mycorrhiza 
Sagan M, Morandi D, Tarenghi E and Duc G 1995 Selection of nodulation and mycorrhizal mutants in the model plant Medicago truncatula (Gaertn.) after gamma-ray mutagenesis Plant Science. 111(1):63-71 
Sagan M, de Larembergue H and Morandi D 1998 Genetic analysis of symbiosis mutants in Medicago truncatula Elmerich C, Kondorosi A, Newton WE (eds) Biological nitrogen fixation for the 21st century. Kluwer, Dordrecht, pp 317?318 
Shaw SL and Long SR 2003 Nod factor elicits two separable calcium responses in Medicago truncatula root hair cells Plant Physiol. 131(3):976-84 
Wais RJ, Galera C, Oldroyd G, Catoira R, Penmetsa RV, Cook D, Gough C, Denarie J and Long SR 2000 Genetic analysis of calcium spiking responses in nodulation mutants of Medicago truncatula Proc Natl Acad Sci U S A. 97(24):13407-12 

Curation Information:
Data entered byChunhong Mao (05/06/2004)
Updated/Verified byChunxia Wang (07/26/2004), Jing Qiu (12/02/2004), Chunhong Mao (12/06/2004)
Final verification statusverified by Chunhong Mao (12/06/2004)