Role of Fungal Factors in Mycorrhizal Formation

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The intricate growth of the VAM fungus within the root cortical cells raises questions as to the molecular nature of key events which permit the symbiosis. The proposed studies will test the role of fungal products in regulating plant mechanisms which could control hyphal development. The hypotheses invoke VAM fungal products to effect plasmalemma function and the defense potential of the host cell. Studies will probe whether fungal products alter key plasmalemma enzyme activities such as ATPase and NAD(P)H oxidase which could regulate ion and nutrient flux between organisms. Effects on defense mechanisms will be studied by screening for altered levels of compounds and enzymes which have putative roles in plant resistance. Molecular biology techniques will be used to determine the extent of changes in plant gene expression which are triggered by VAM fungal components.%%% Healthy plant development may require symbiosis to be established between the plant root and certain beneficial fungi which form mycorrhizae. Approximately 90% of all higher plants form vesicular-arbuscular (VA) mycorrhizae. VA mycorrhizae are produced by the colonization of the cortical cells of fine feeder roots of plants by fungal hyphae. The hyphae extend out into the soil and create an enhanced feeding area from which nutrients can be extracted and utilized by the plant. Mycorrhizal plants often demonstrate increased uptake of phosphorus, trace metals and other sparingly soluble nutrients. Greater tolerance to drought and improved resistance to some root diseases have been reported for mycorrhizal plants. Consequently mycorrhizal plants frequently exhibit increased growth yield and survival over non-mycorrhizal plants especially on less fertile soil. These beneficial effects of VAM formation hold considerable potential for improving plant production in agriculture, forestry, reclamation, and horticulture. These improvements will reduce energy-related costs directly through reduction in fertilizer and water requirements and indirectly by the production of more robust plants.***//