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Title: Symbiotic characterization of isoleucine + valine and leucine auxotrophs of Sinorhizobium meliloti
Authors: Hassani, Raad
Prasad, C Krishna
Vineetha, K E
Vij, Neeraj
Singh, Prachi
Sud, Reeteka
Yadav, Sangeeta
Randhawa, Gursharn S
Issue Date: Oct-2002
Publisher: NISCAIR-CSIR, India
Abstract: Ten isoleucine+valine and three leucine auxotrophs of Sinorhizobium meliloti  Rmd201 were obtained by random mutagenesis with transposon Tn5 followed by screening of Tn5 derivatives on minimal medium supplemented with modified Holliday pools. Based on intermediate feeding, intermediate accumulation and cross-feeding studies, isoleucine+valine and leucine auxotrophs were designated as ilvB/ilvG, ilvC and ilvD, and leliC/leliD and leliB mutants, respectively. Symbiotic properties of all ilvD mutants with alfalfa plants were similar to those of the parental strain. The ilvB/ilvG and ilvC mutants were Nod . Inoculation of alfalfa plants with ilvB/ ilvG mutant did not result in root hair curling and infection thread formation. The ilvC mutants were capable of curling root hairs but did not induce infection thread format ion. All leucine auxotrophs were Nod+ Fix-. Supplementation of leucine to the plant nutrient medium did not restore symbiotic effectiveness to the auxotrophs. Histological studies revealed that the nodules induced by the leucine auxotrophs did not develop fully like those induced by the parental strain. The nodules induced by leuB mutants were structurally more advanced than the leliC/leliD mutant induced nodules. These results indicate that ilvB/ilvG, ilvC and one or two leu genes of S. meliloti may have a role in symbiosis. The position of ilv genes on the chromosomal map of S. meliloti was found to be near ade-15 marker.
Page(s): 1110-1120
ISSN: 0975-1009 (Online); 0019-5189 (Print)
Appears in Collections:IJEB Vol.40(10) [October 2002]

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