Rhizobium nod genes are involved in inducing an early nodulin gene

Temporal and spatial regulation of the symbiotic genes of Rhizobium meliloti in planta revealed by transposon Tn5-gusA.

“…Disappearance could reflect a specific signal, which may be part of the nodule cells senescence program but cannot reflect general cell death because genes of the Nil pattern continue to be expressed at this time. Interestingly, the early pea nodulin ENOD2, which seems to be induced by a signal based on nod expression (Govers et al 1986;Dickstein et al 1988), also declines later in nodule development (Franssen et al 1987). Such observations remain to be reconciled with indirect evidence suggesting effects of nod expression later in development on exo gene function in R. meliloti (Klein et al 1988) and on induction of vetch nodulins by Rhizobium leguminosarum (Nap et al 1989).…”

Nodulin Gene Expression in Effective Alfalfa Nodules and in Nodules Arrested at Three Different Stages of Development

“…Translation reactions were incubated with 10 ,uL of antiserum as described (9), except that 10 mg of Sepharose-Protein A (Pharmacia) were added in the final 3 h of incubation. The Sepharose-A-bound immunoprecipitates were pelleted gently in a microfuge and washed with buffer five times, until negligible counts per minute were detected in the supernatant.…”

Plant gene expression in early stages of Rhizobium-legume symbiosis

“…For the pea-Rhizobium leguminosarum symbiosis it has been suggested that the nod genes, which are located on the symbiotic plasmid, are involved in the induction of early nodulin genes (Govers et al, 1986), while genes not located on this plasmid but probably on the chromosome, or another plasmid of Rhizobium leguminosarum are required for the induction of the other nodulin genes. It is still unclear which genes of Bradyrhizobium japonicum are involved in nodulin gene expression, but our results show that they are not located in the region in which the nifH,DK genes are located since the mutants F4-6 and 45K-13, despite large deletions covering together about 150 kb around this nifH,DK region (M. Hahn, personal communication) are still able to induce expression of all nodulin genes.…”

“…From a cDNA library, prepared against soybean nodule mRNA, clone pGmENOD2 hybrid selected mRNAs encoding Ngm-75 (Franssen et al, 1987). Using this clone homologous ENOD2 mRNA was demonstrated to occur in pea (Govers et al, 1986), vetch (Moerman ef al., 1987), bean (Padillaefa/., 1988), alfalfa (Dickstein et al, 1988, sesbania (N. Chua, personal communication), clover and birdsfoot trefoil (F. Govers, personal communication). The amino acid sequence of the ENOD2 protein derived from the nucleotide sequence of the soybean cDNA and genomic GmENOD2 clones revealed that this protein has an N-terminal signal peptide followed by a sequence of two repeating elements: Pro-Pro-Glu-Tyr-GIn and Pro-Pro-His-Glu-Lys (Franssen era/., 1987 and in prep).…”

“…But the steps in root nodule formation show that major decisions determining the development of a root nodule are made in the stages preceding the establishment mentof a nitrogen fixing nodule. We have shown that nodulin genes are differentially expressed during development (Govers et al, 1986;Gloudemans et al, 1987) and that in pea at least two nodulin genes are transcribed in the second stage of root nodule formation. These genes are referred to as early nodulin genes.…”