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Cloning and analysis of exo gene required for nodule invasion and development of Rhizobium astragali

Huang Jianbin, Zhou Beiyun, Song Hongyu

Shanghai Institute of Plant Physiology,The Chinese Academy of Sciences.Shanghai 200032

Abstract

Three exopolysaccharide (EPS)-deficient mutants NA-01, 02, 04 (Exo~(-)) isolated from wild Rhizobium astragali strains 107 showed no ability to induce nodule formation on the roots of Astragalus sinicus L. From plasmid exo-R^-11 which could complement these three mutants, a 2.6 kb DNA fragment was cloned using 3.1 kb fragment from mutant site of NA-01 as probe. It was shown that the 2.6 kb fragment did not only fully complemented the EPS phenotype of each of the three mutants, but also restored its ability to induce Fix~(+) nodule formation as did the wild-type strain 107. After Tn5 site-directed mutagenesis, the 2.6 kb DNA with Tn5 insertion lost such complementation ability. Therefore, we could conclude that 2.6 kb DNA fragment contained the exo gene which complements the three mutants.

Key words: exo gene;Cloning;Exopolysaccaride;Rhizobium astragali

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Citing This Article：

Huang Jianbin, Zhou Beiyun, Song Hongyu. Cloning and analysis of exo gene required for nodule invasion and development of Rhizobium astragali. Acta Physiol Sin 1997; 49 (3): (in Chinese with English abstract).