The Lotus japonicus ndx gene family is involved in nodule function and maintenance.
To elucidate the function of the ndx homeobox genes during the Rhizobium-legume symbiosis, two Lotus japonicus ndr genes were expressed in the antisense orientation under the control of the nodule-expressed promoter Psenod12 in transgenic Lotus japonicus plants. Many of the transformants obtained segregated into plants that failed to sustain proper development and maintenance of root nodules concomitant with down-regulation of the two ndx genes. The root nodules were actively fixing nitrogen 3 weeks after inoculation, but the plants exhibited a stunted growth phenotype. The nodules on such antisense plants had under-developed vasculature and lenticels when grown on medium lacking nitrogen sources. These nodules furthermore entered senescence earlier than the wild-type nodules. Normal plant growth was resumed upon external addition of nitrogen. This suggests that assimilated nitrogen is not properly supplied to the plants in which the two ndx genes are down-regulated. The results presented here, indicate that the ndx genes play a role in the development of structural nodule features, required for proper gas diffusion into the nodule and/or transport of the assimilated nitrogen to the plant.
Grønlund
Mette
M
Laboratory of Gene Expression, Department of Molecular Biology, Aarhus University, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark.
Gustafsen
Camilla
C
Roussis
Andreas
A
Jensen
Dorte
D
Nielsen
Lars Peter
LP
Marcker
Kjeld A
KA
Jensen
Erik Ostergaard
EO
D002467:Cell Nucleus / Q000378:metabolism; D016373:DNA, Antisense / Q000235:genetics; D015536:Down-Regulation / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D018398:Homeodomain Proteins / Q000235:genetics* / Q000502:physiology; D000070116:Lotus / Q000235:genetics*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins; D018517:Plant Roots / Q000235:genetics* / Q000382:microbiology; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012231:Rhizobium / Q000254:growth & development; D013559:Symbiosis / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects
D016373:DNA, Antisense; D005938:Glucocorticoids; D018398:Homeodomain Proteins; D008164:Luminescent Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C120056:ndx1 protein, plant; D049452:Green Fluorescent Proteins