THE NODDABC GENES OF RHIZOBIUM-LEGUMINOSARUM BIOVAR TRIFOLII CONFER ROOT-HAIR CURLING ABILITY TO A DIVERSE RANGE OF SOIL BACTERIA AND THE ABILITY TO INDUCE NOVEL ROOT SWELLINGS ON BEANS
J. Plazinski et al., THE NODDABC GENES OF RHIZOBIUM-LEGUMINOSARUM BIOVAR TRIFOLII CONFER ROOT-HAIR CURLING ABILITY TO A DIVERSE RANGE OF SOIL BACTERIA AND THE ABILITY TO INDUCE NOVEL ROOT SWELLINGS ON BEANS, Australian journal of plant physiology, 21(3), 1994, pp. 311-325
Cloned DNA fragments coding for the nodDABC genes of Rhizobium legumin
osarum biovar trifolii strain ANU843 were introduced into Rhizobium st
rains possessing Sym plasmid deletions. These strains were able to: (a
) synthesise four butanol-soluble Nod metabolites; (b) affect the norm
al growth pattern of plant root hairs of a wide range of host and non-
host legumes; and (c) induce many root outgrowths on Phaseolus plants.
The four Nod metabolites produced by these strains were labelled by s
upplying cultures with C-14-acetate in the presence of a flavonoid ind
ucer of nod gene expression. In contrast, more than ten Nod metabolite
s were synthesised by wild-type strains or constructed strains contain
ing the full complement of R. leguminosarum biovar. trifolii nodulatio
n and host specific nodulation genes. Strain ANU845 containing nodDABC
did not induce infection threads or nodule initiation sites but disto
rted and curled cells in plant root hairs. However strain ANU845 induc
ed root outgrowths on beans (Phaseolus vulgaris) that appeared to resu
lt from a proliferation of the epidermal tissue. Transfer of plasmids
bearing nodDABC to various Gram-negative bacteria, Agrobacterium tumef
aciens, Pseudomonas aeruginosa, Lignobacter sp., Azospirillum brasilen
se and Escherichia coli, and different non-nodulating mutant rhizobia
conferred on these strains the ability to cause root-hair curling and
distortions. Several strains induced root-hair curling on clover and a
range of other non-host legumes. We suggest that the expression of no
dDABC in a range of soil bacteria may extend or alter the effects of t
hese soil bacteria on the roots of host plants.