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Genomic Science Program

2008 Awardee

Identification of Genes that Regulate Phosphate Acquisition and Plant Performanceduring Arbuscular Mycorrhizal Symbiosis in Medicago truncatula and Brachypodium distachyon

INVESTIGATORS: Maria J. Harrison 1 and Matthew E. Hudson 2

INSTITUTION: 1 Boyce Thompson Institute for Plant Research and 2 University of Illinois

NON-TECHNICAL SUMMARY: Most vascular flowering plants have the ability to form symbiotic associations with arbuscular mycorrhizal (AM) fungi. The symbiosis develops in the roots and can have a profound effect on plant productivity, largely through improvements in plant mineral nutrition. Within the root cortical cells, the plant and fungus create novel interfaces specialized for nutrient transfer, while the fungus also develops a network of hyphae in the rhizosphere. Through this hyphal network, the fungus acquires and delivers phosphate and nitrogen to the root. In return, the plant provides the fungus with carbon. In addition, to enhancing plant mineral nutrition, the AM symbiosis has an important role in the carbon cycle, and positive effects on soil health.

OBJECTIVES: The overall goals are to identify and characterize plant genes involved in the regulation and functioning of the AM symbiosis in Medicago truncatula and Brachypodium distachyon . The specific objectives are: 1) Identify and characterize M. truncatula transcription factors expressed in mycorrhizal roots. 2) Identify transcription factors required for development of the arbuscule-cortical cell interface and symbiotic phosphate transport. 3) Investigate the molecular basis of functional diversity among AM symbioses in B. distachyon and identify gene expression patterns associated with AM symbioses that differ functionally with respect to plant performance. 4) Analyze the predicted B. distachyon ortholog of MtPT4 and its role in symbiotic phosphate transport.

APPROACH: 1) Laser capture microdissection coupled with sequence-based transcript profiling will be used to identify and characterize the expression of transcription factors in M. truncatula mycorrhizal roots. 2) RNAi will be used to down-regulate transcription factor gene expression and the effects on development of the AM symbiosis and AM symbiosis-induced gene expression will be assessed. 3) Sequence-based transcript profiling will be used to monitor B. distachyon root and shoot transcript profiles in AM symbioses that differ functionally with respect to plant performance. 4) A putative B. distachyon ortholog of MtPT4, a transporter critical for symbiotic phosphate transport in M. truncatula , has been identified. RNAi will be used to down-regulate BdPT4 and its role in symbiotic phosphate transport will be analyzed.

Name: Maria J. Harrison
Phone: 607-254-6472
Fax: 607-254-6779



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