Plant & Animal Genomes XV Conference

January 13-17, 2007
Town & Country Convention Center
San Diego, CA

Exploiting The Potential Of Brachypodium distachyon: Functional Genomic Analyses Of Interactions With The Rice Blast Pathogen Magnaporthe grisea.

Luis A J Mur¹ , William Allwood¹ , Joel V Smith¹ , Andrew P M Routledge¹ , David I Ellis² , Royston Goodacre²

¹  University of Wales Aberystwyth, Institute of Biological Science Edward Llwyd Building, Aberystywth, Wales SY23 3DA, United Kingdom

²  University of Manchester, Department of Chemistry PO Box 88 Sackville Street, Manchester, M60 1QD, UK

Brachypodium distachyon exhibits differential interactions with a range of economically important cereal pathogens. Magnaporthe grisea is the causal agent of Rice Blast disease which is the source of considerable crop losses. Extensive screens of B. distachyon accessions with M. grisea strain Guy-11 has identified interactions which exhibited blast symptoms that were indistinguishable from those forming on rice. Further, a resistance mechanism based on a single genetic trait was identified. Functional genomic analyses of the responses of accessions ABR1 (susceptible) and ABR5 (resistant) have been initiated. Besides revealing key events in disease progression, these studies demonstrate the utility of B. distachyon for post-genomic analyses.
Metabolomic approaches have employed Fourier-transform Infrared spectroscopy (FT-IR) for high-through put metabolomic fingerprinting and Electrospray ionization mass spectrometry (ESI-MS) for metabolomic profiling. Data mining approaches used Discriminant function analysis (DFA) distinguished between disease symptoms and plant resistance. The data were validated via DFA projection analyses which indicated that experiments involving B. distachyon produced highly reproducible results. Mass-ions targeted as substances involved in early disease symptoms or the elicitation of resistance were identified as phosphatidic acids and phosphatidyl glycerol (PG) phospholipids. PG-phospholipids are a source of jasmonate (JA) defence signals which was shown to accumulate in response to M. grisea. In a complementary approach a cDNA subtracted library was constructed from disease –exhibiting ABR1. Microarrays were derived from this library and differentially screened for defence-regulated transcripts. Amongst those transcripts which were highly up-regulated were those encoding enzymes involved in indole biosynthesis which may be a source of antimicrobial phytoalexins. Interestingly, these genes were also found to be regulated by JA. These approaches are currently being extended to examine other B. distachyon – pathogen interactions.