Truncated hemoglobins in actinorhizal nodules of Datisca glomerata.
Three types of hemoglobins exist in higher plants, symbiotic, non-symbiotic, and truncated hemoglobins. Symbiotic (class II) hemoglobins play a role in oxygen supply to intracellular nitrogen-fixing symbionts in legume root nodules, and in one case ( Parasponia Sp.), a non-symbiotic (class I) hemoglobin has been recruited for this function. Here we report the induction of a host gene, dgtrHB1, encoding a truncated hemoglobin in Frankia-induced nodules of the actinorhizal plant Datisca glomerata. Induction takes place specifically in cells infected by the microsymbiont, prior to the onset of bacterial nitrogen fixation. A bacterial gene (Frankia trHBO) encoding a truncated hemoglobin with O (2)-binding kinetics suitable for the facilitation of O (2) diffusion ( ) is also expressed in symbiosis. Nodule oximetry confirms the presence of a molecule that binds oxygen reversibly in D. glomerata nodules, but indicates a low overall hemoglobin concentration suggesting a local function. Frankia trHbO is likely to be responsible for this activity. The function of the D. glomerata truncated hemoglobin is unknown; a possible role in nitric oxide detoxification is suggested.
Pawlowski
K
K
Department of Plant Biochemistry, Göttingen University, 37077 Göttingen, Germany. pawlowski@botan.su.se
Jacobsen
K R
KR
Alloisio
N
N
Ford Denison
R
R
Klein
M
M
Tjepkema
J D
JD
Winzer
T
T
Sirrenberg
A
A
Guan
C
C
Berry
A M
AM
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000737:chemistry / Q000378:metabolism; D040161:Frankia / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D006454:Hemoglobins / Q000235:genetics* / Q000378:metabolism; D019684:Magnoliopsida / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D009586:Nitrogen Fixation; D010100:Oxygen / Q000378:metabolism; D010940:Plant Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D053204:Root Nodules, Plant / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D013559:Symbiosis
D001426:Bacterial Proteins; D018076:DNA, Complementary; D006454:Hemoglobins; D010940:Plant Proteins; D010100:Oxygen