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作者 Abubaker, Jehad
書名 Carbon metabolism and gene regulation in arbuscular mycorrhizal fungi
國際標準書號 0496845073
book jacket
說明 223 p
附註 Source: Dissertation Abstracts International, Volume: 65-06, Section: B, page: 2769
Chair: Peter J. Lammers
Thesis (Ph.D.)--New Mexico State University, 2004
The arbuscular mycorrhizal (AM) symbiosis is ancient, widespread and vital to the life of land plants. A large fraction of land plants including angiosperms, gymnosperms, pteridophytes, some mosses, lycopods, and psilotales are colonized. For most plants, mycorrhizas, not roots, are the chief organs of nutrient uptake, thus the study of AM fungi is of practical importance in agriculture, horticulture, reforestation, and ecosystem management. The plant benefits from enhanced mineral uptake while the AM fungus receives all its carbon from the host in the form of hexose. Measurements of carbon flux and gene expression were used to identify fungal pathways for carbon utilization and regulation. Hexose was shown to be directly incorporated into trehalose, glycogen and lipid based on labeling experiments, suggesting that carbon taken up in the root is exported to the ERM. Lipids, a dominant form of stored carbon in the fungal partner and which fuels spore germination, is made by the fungus from carbohydrates within the root and is exported to the ERM. The ERM does not use exogenous hexoses for catabolism, storage or transfer to the host; the fungus only utilizes hexoses taken up in the IRM. Results from addition of 13C2-acetate and 13C2-glycerol to the extraradical mycelium (ERM) indicate that glyoxylate cycle is central to the flow of carbon in the AM symbiosis
Quantitative real-time polymerase chain reaction assays were developed for measuring the expression of genes involved in key carbon metabolic pathways including lipid breakdown, gluconeogenesis, trehalose breakdown, glycogen synthesis, chitin synthesis, oxidative pentose phosphate pathway (OPPP). The transcriptional regulation of these genes was studied in response to treatment with glucose and plant root exudates. Glucose addition to mycorrhizal roots transiently down-regulated both the glyoxylate cycle and gluconeogenesis in the IRM as expected. Expression of the same genes was up-regulated in the IRM relative to controls several days after glucose addition, indicative of a shift back to gluconeogenic metabolism. Semi-purified root exudates caused a rapid and significant increase in gluconeogenesis, OPPP, chitin and glycogen synthesis relative to the control in germinating spores, demonstrating that compounds in the exudates control fungal metabolism prior to colonization
School code: 0143
DDC
Host Item Dissertation Abstracts International 65-06B
主題 Biology, Molecular
Biology, Microbiology
Biology, Plant Physiology
0307
0410
0817
Alt Author New Mexico State University
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