Nodulation gene mutants of Mesorhizobium loti R7A-nodZ and nolL mutants have host-specific phenotypes on Lotus spp.
Rhizobial Nod factors induce plant responses and facilitate bacterial infection, leading to the development of nitrogen-fixing root nodules on host legumes. Nodule initiation is highly dependent on Nod-factor structure and, hence, on at least some of the nodulation genes that encode Nod-factor production. Here, we report the effects of mutations in Mesorhizobium loti R7A nodulation genes on nodulation of four Lotus spp. and on Nod-factor structure. Most mutants, including a DeltanodSDeltanolO double mutant that produced Nod factors lacking the carbamoyl and possibly N-methyl groups on the nonreducing terminal residue, were unaffected for nodulation. R7ADeltanodZ and R7ADeltanolL mutants that produced Nod factors without the (acetyl)fucose on the reducing terminal residue had a host-specific phenotype, forming mainly uninfected nodule primordia on Lotus filicaulis and L. corniculatus and effective nodules with a delay on L. japonicus. The mutants also showed significantly reduced infection thread formation and Nin gene induction. In planta complementation experiments further suggested that the acetylfucose was important for balanced signaling in response to Nod factor by the L. japonicus NFR1/NFR5 receptors. Overall the results reveal differences in the sensitivity of plant perception with respect to signaling leading to root hair deformation and nodule primordium development versus infection thread formation and rhizobial entry.
Rodpothong
Patsarin
P
Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.
Sullivan
John T
JT
Songsrirote
Kriangsak
K
Sumpton
David
D
Cheung
Kenneth W J-T
KW
Thomas-Oates
Jane
J
Radutoiu
Simona
S
Stougaard
Jens
J
Ronson
Clive W
CW
D020561:Alphaproteobacteria / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D005647:Fucosyltransferases / Q000235:genetics* / Q000378:metabolism; D054884:Host-Pathogen Interactions; D000070116:Lotus / Q000382:microbiology*; D009154:Mutation; D010641:Phenotype; D055170:Plant Root Nodulation / Q000502:physiology
D001426:Bacterial Proteins; C117779:noIL protein, Rhizobium etli; D005647:Fucosyltransferases; C103941:NodZ protein, bacteria