The Expression Mechanism of Leghemoglobin Geno of Leguminous Plant.

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Leghemoglobins (Lbs) are small monomeric heme proteins synthesized exclusively in the root nodules that develope due to the rhizobial infection to leguminous plant. The induction of Lb-genes occurs only after bacterial infection but is independent of the expression of nif-gene in bacteroid. The Lb-gene expression of root cells are induced by some signals derived from the invaded bacteria. The signals are not Known about the details although nod- and nif-gene have been analyzed about the loci on Sym-plasmid and nucleotide sequences.The cell, leghemoglobin is synthesized at the most early step of nodulation, has been determined by an indirect-immunological technique.For analysis the expression of Lb-induction gene(Lb-ind gene), Lb-gene has been cloned with the mRNA of root nodule : reverse transcriptase system. The total DNA from R. trifolii 4S(Nod^+, Lb^+, Fix^+) was isolated and digested with Sau3AI. The DNA fragments were ligated with cosmid vector pCKS 13 and packaged in <lambda>-phage head. The recombinant DNA including in E. coli cells were transferred to R. trifolii Qn1(Nod^+,Lb^-, Fix^-) by triparental mating method, and then inoculated to seedilings of white clover. A strain NL18(Nod^+, Lb^+, Fix^-) was screened out form a nodule. The locus and size of Lb-ind gene on the cloning DNA from R. trifolii 4S was discussed in this study.