title: Rhizobium nodulation genes involved in root hair curling (Hac) are functionally conserved.
abstract: Five specific transposon-induced nodulation defective (Nod(-)) mutants from different fast-growing species ofRhizobium were used as the recipients for the transfer of each of several endogenous Sym(biosis) plasmids or for recombinant plasmids that encode early nodulation and host-specificity functions. The Nod(-) mutants were derived fromR. trifolii, R. meliloti and from a broad-host-rangeRhizobium strain which is able to nodulate both cowpea (tropical) legumes and the non-legumeParasponia. These mutants had several common features (a), they were Nod(-) on all their known plant hosts, (b), they could not induce root hair curling (Hac(-)) and (c), the mutations were all located on the endogenous Sym-plasmid of the respective strain. Transfer to these mutants of Sym plasmids (or recombinant plasmids) encoding heterologous information for clover nodulation (pBR1AN, pRt032, pRt038), for pea nodulation (pJB5JI, pRL1JI::Tn1831), for lucerne nodulation (pRmSL26), or for the nodulation of both tropical legumes and non-legumes (pNM4AN), was able to restore root hair curling capacity and in most cases, nodulation capacity of the original plant host(s). This demonstrated a functional conservation of at least some genes involved in root hair curling. Positive hybridization between Nod DNA sequences fromR. trifolii and from a broad-host-rangeRhizobium strain (ANU240) was obtained to other fast-growingRhizobium strains. These results indicate that at least some of the early nodulation functions are common in a broad spectrum ofRhizobium strains.
authors: Department of Genetics, Research School of Biological Sciences, Australian National University, P.O. Box 475, 2601, Canberra City, Australia.
authors: M A
authors: MA
authors: Djordjevic
authors: P R
authors: PR
authors: Schofield
authors: R W
authors: RW
authors: Ridge
authors: N A
authors: NA
authors: Morrison
authors: B J
authors: BJ
authors: Bassam
authors: J
authors: J
authors: Plazinski
authors: J M
authors: JM
authors: Watson
authors: B G
authors: BG
authors: Rolfe