Germinating spores of Glomus intraradices can use internal and exogenous nitrogen sources for de novo biosynthesis of amino acids.
* Here, nitrogen (N) uptake and metabolism, and related gene expression, were analyzed in germinating spores of Glomus intraradices to examine the mechanisms and the regulation of N handling during presymbiotic growth. * The uptake and incorporation of organic and inorganic N sources into free amino acids were analyzed using stable and radioactive isotope labeling followed by high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS) and liquid scintillation counting and the fungal gene expression was measured by quantitative polymerase chain reaction (Q-PCR). * Quiescent spores store Asp, Ala and Arg and can use these internal N resources during germination. Although not required for presymbiotic growth, exogenous N can also be utilized for the de novo biosynthesis of amino acids. Ammonium and urea are more rapidly assimilated than nitrate and amino acids. Root exudates do not stimulate the uptake and utilization of exogenous ammonium, but the expression of genes encoding a putative glutamate dehydrogenase (GDH), a urease accessory protein (UAP) and an ornithine aminotransferase (OAT) were stimulated by root exudates. The transcript levels of an ammonium transporter (AMT) and a glutamine synthetase (GS) were not affected. * Germinating spores can make effective use of different N sources and the ability to synthesize amino acids does not limit presymbiotic growth of arbuscular mycorrhizal (AM) spores.
Gachomo
Emma
E
South Dakota State University, Biology and Microbiology Department, Brookings, SD 57007, USA.
Allen
James W
JW
Michigan State University, Plant Biology Department, East Lansing, MI 48824-1312, USA.
Pfeffer
Philip E
PE
USDA, ARS, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA.
Govindarajulu
Manjula
M
New Mexico State University, Department of Chemistry and Biochemistry, Las Cruces, NM 88003, USA.
Douds
David D
DD
USDA, ARS, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA.
Jin
Hairu
H
USDA, ARS, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA.
Nagahashi
Gerald
G
USDA, ARS, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA.
Lammers
Peter J
PJ
New Mexico State University, Department of Chemistry and Biochemistry, Las Cruces, NM 88003, USA.
Shachar-Hill
Yair
Y
Michigan State University, Plant Biology Department, East Lansing, MI 48824-1312, USA.
Bücking
Heike
H
South Dakota State University, Biology and Microbiology Department, Brookings, SD 57007, USA.
D000596:Amino Acids / Q000096:biosynthesis*; D001692:Biological Transport; D008401:Gas Chromatography-Mass Spectrometry; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D055137:Glomeromycota / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D005969:Glutamate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D038821:Mycorrhizae / Q000254:growth & development / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009953:Ornithine-Oxo-Acid Transaminase / Q000235:genetics / Q000378:metabolism; D053147:Plant Exudates / Q000502:physiology; D018517:Plant Roots; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D013172:Spores, Fungal / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D014508:Urea / Q000378:metabolism
D000596:Amino Acids; D009566:Nitrates; D053147:Plant Exudates; D000644:Quaternary Ammonium Compounds; D014508:Urea; D005969:Glutamate Dehydrogenase; D009953:Ornithine-Oxo-Acid Transaminase; D009584:Nitrogen