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Abstract Detail

Plant-Symbiont Interactions

Pislariu, Catalina I [1], Morris, Viktoriya [2], Lee, Yi-Ching [2], Wessler, Heath G [2], McKethan, Brandon [2], Veereshlingam, Harita [2], Gann, Janine G [3], Sherrier, Janine [4], Dickstein, Rebecca [2].

Genes required for rhizobial invasion and root nodule development in Medicago truncatula.

When elicited with compatible rhizobia, leguminous plants develop new organs, root nodules, which host the bacterial symbionts that are capable of nitrogen fixation. Following an initial exchange of biochemical signals, compatible rhizobia that synthesize specific Nod factors (NFs) gain access to newly divided inner cortical cells. The passage of rhizobia through several cell layers into the nodule primordia occurs through plant-derived, tube-like structures called infection threads (ITs). Once deposited inside host cells, rhizobia differentiate into the nitrogen-fixing form, the bacteroids.
From an EMS-mutagenized population of Medicago truncatula (1), we identified two nodulation mutants: nip (numerous infections with polyphenolics) (2) and sli (sluggish infection) (3). Nip has bump-like nodules that are blocked early in nodulation, accumulate polyphenols, and contain hypertrophic ITs from which rhizobia are only occasionally released and do not differentiate into bacteroids. Three nip alleles have been tentatively identified: nip-1 (2, 3), latd (4), and nip-3 (5). In sli, infection threads reach nodule primordia but further nodule development was found in only ~5% of a sli population. Grafting experiments showed that the nip and sli phenotypes are root-controlled. Both nip and sli have very distinctive lateral root phenotypes.
Current efforts are directed towards cloning NIP and a better understanding of the sli phenotype. To clone NIP, we are using a positional approach. Genotyping of 2277 plants from the mapping populations has permitted the identification of 38 plants with recombination events between 146o17 and 23c16, markers which flank NIP. We are refining the physical and the genetic Medicago maps in this region in our continuing efforts to clone NIP.

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1 - University of North Texas, Biological Sciences, Chestnut and Avenue C, P.O.Box 305220, Denton, TX, 76201-5220, USA
2 - University of North Texas, Biological Sciences
3 - Delaware Biotechnology Institute and University of Delaware, Plant and Soil Sciences, 15 Innovation Way, Newark, DE, 19711, USA
4 - University of Delaware

nitrogen fixation
Legume nodulation
Medicago truncatula
nodulation mutants
nip and sli.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P16017
Abstract ID:1898

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