Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 14, 2012
Publication Date: August 4, 2012
Citation: Samac, D.A., Dornbusch, M.R., Foster-Hartnett, D., Tu, Z.J., Gantt, J.S. 2012. Role of a putative amino acid transporter in fungal disease resistance in alfalfa [abstract]. American Phytopathological Society Annual Meeting, August 4-8, 2012, Providence, Rhode Island. Available: http://www.apsnet.org/meetings/Documents/2012_Meeting_Abstracts/aps12abP616.htm. Technical Abstract: Accessions of the model legume Medicago truncatula, a close relative of alfalfa, were identified that are resistant to several foliar pathogens, and microarray technology was used to identify genes specifically expressed in the resistance response. A large proportion of the up-regulated genes had only weak similarity to known genes or had no significant matches in the database. Transgenic alfalfa (M. sativa) plants were produced that expressed interfering RNA (RNAi) constructs of selected genes to evaluate their role in disease resistance. Expression of RNAi resulted in a 60-98% reduction in specific transcripts. Down-regulation of a putative transmembrane lysine-histidine transporter (LHT) and hydroxyisoflavanone dehydratase (HID) resulted in susceptibility to the anthracnose pathogen Colletotrichum trifolii. HID catalyzes the production of formononetin, a precursor in synthesis of the phytoalexin medicarpin. Expression profiling of an LHT RNAi line using RNA-seq with and without inoculation with C. trifolii found mis-regulation of genes involved in secondary metabolism, carbohydrate metabolism, protein modification, transport, and amino acid metabolism. Down-regulation of early nodulin 12A and a putative BZIP transcription factor had no effect on resistance to C. trifolii. These results provide further evidence for a critical role of isoflavonoid compounds in disease resistance and identify a novel gene involved in resistance to fungal pathogens in alfalfa.