The pea early nodulin gene PsENOD7 maps in the region of linkage group I containing sym2 and leghaemoglobin

Abstract

The early nodulin gene, PsENOD7, is expressed in pea root nodules induced by Rhizobium leguminosarum bv. viciae, but not in other plant organs. In situ hybridization showed that this gene is transcribed during nodule maturation in the infected cells of the proximal part of the prefixation zone II. At the transition of zone II into interzone II-III, the level of PsENOD7 mRNA drops markedly. PsENOD7 has no significant homology to other genes. RFLP mapping studies have shown that PsENOD7 is located in linkage group I between the leghaemoglobin genes and sym2.Rhizobium leguminosarum bv. viciae induces the formation of nitrogen fixing root nodules on the roots ofPisum sativum (pea). By mutagenesis and genetic studies several plant genes essential for normal nodule development have been identified and these genes have been named sym genes. In pea about 30 different sym genes have been described [7,18,19,26]. The sym genes are distributed randomly on the seven linkage groups of pea [19], but several sym genes, namely sym2, sym5, syml9 and nod3, are clustered on linkage group I, near the major leghaemoglobin (Lb) locus [32, 381.The different stages of legume nodule development are accompanied by the expression of plant genes, the so-called nodulin genes. These genes, that are only expressed during nodule development, have been divided into early and late nodulin genes; the early nodulin genes are expressed before the bacteria start to fix nitrogen, whereasThe nucleotide sequence data reported will appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession number X93172.

Genetic mapping and functional analysis of a nodulation-defective mutant (sym19) of pea (Pisum sativum L.)

“…Subsequently Kozik (1996) concluded that sym19 must be linked to ENOD40, about 17 cM from sym2 on linkage group I.…”

“…While numerous bacterial genes have been identi®ed, there has been limited progress in identi®cation of plant genes that have a de®ned role in nodule development. As a ®rst step towards identifying such genes, numerous plant mutants defective in nodulation (Sagan et al 1994, Kozik 1996 and references therein) have been isolated. One such pea mutant, line P55, is defective for the rhizobial and endomycorrhizial symbioses (Duc and Messager 1989;Sagan et al 1994).…”

Actinorhizal, mycorhizal and rhizobial symbioses: how much do we know?

“…Expression of the early nodulin gene ENOD40 is localized in pericycle zone of root and can be induced by exogenous application of Nod factors (for review see Pawlowski and Bisseling, 1996). In P. sativum nodules, ENOD7 gene is expressed in the proximal part of the prefixation zone II (Kozik et al, 1996). In legume nodules, ENOD2, MtPRP and nodule-specific lectin gene are expressed in parenchyma and these products provide an O 2 diffusion barrier in order to preserve nitrogenase activity (for review see Pawlowski, 1997).…”

Microsynteny between the Medicago truncatula SYM2-orthologous genomic region and another region located on the same chromosome arm

“…Linkage group I of pea is the genomic region with the highest density of legume genes involved in the symbiosis with Rhizobium leguminosarum bv viciae, containing several symbiotic genes within a 20-cM interval (Weeden et al 1990;Temnykh et al 1995a, b;Kozik et al 1996;Schneider et al 1999). One of these genes is SYM2 that was first identified in the pea accession 'Afghanistan' where it controls infection by rhizobia in a Nod factor structure-dependent manner (Firmin et al 1993;Geurts et al 1997).…”