At least the first- and second-cell stage of biotrophic infection. This is the first account to indicate what metabolites the plant does not provide M. oryzae during colonization, thus shedding light on both plant host and fungal pathogen metabolism. This study also demonstrates the utility of combining biochemical genetics with live-cell-imaging to answer fundamental questions regarding the host cell nutrient environment.To inoculate plates, filter stocks were revived on CM and 10 mm2 blocks of mycelium were transferred to the center of each plate. Strains were grown for 10?6 days at 26uC with 12 hr light/dark cycles. After 10 days of growth, plate images were taken with a Sony Cyber-shot digital camera, 14.1 mega pixels. Fungal spores were counted on a haemocytometer (Corning) following harvesting in sterile distilled water from 14-day-old plates. For appressorial development assays, 200 ml of a 16105 spores ml21 spore suspension was added to plastic coverslips mounted on a glass slide support and placed in a glass dish, with moisture, for 24 hr. Rates of appressorium 15481974 formation were determined by counting the number of appressoria formed by 50 conidia after 24 hr. This was repeated three times for each strain.Analysis of the distribution of STR3 orthologues across the fungal kingdomWe used the Fungal Genome Collection (FGC) website (http:// bioinfolab.unl.edu/emlab/FGC/) to search through the STR3 (MGG_07074) orthologues from 81 genomes across the fungal kingdom. The specific description and screen-shots detailing this analysis can be found in the “Use Cases” page of the FGC website. Further confirmation was done by reciprocal BLAST [28] between S. cerevisiae and other fungal genomes; potential orthologue(s) in each species was queried against the S. cerevisiae genome, returning STR3 as the highest scoring hit. We confirmed that each genome contained a single copy of the STR3 orthologue. Protein sequences of orthologue candidates were aligned using MAFFT [29]. Nearly all STR3 orthologues displayed high sequence similarity (.60 ) and coverage (.85 ) except for the extra C-terminal region (mevalonate kinase domain) found in the Basidiomycota as mentioned above. Phylogenetic analysis was done using RAxML version 7.0.4 [30] with the WAG substitution matrix and the gamma distribution parameter estimated. Bootstrap analysis for branch support was done with 1000 pseudoreplicates. The alignment and phylogenetic analysis were done bothMaterials and Methods Strain growth conditions and physiological testsThe strains used in this study were derived from Guy11 and maintained as filter stocks at 220uC in the Wilson laboratory. Strains were grown on complete medium (CM) containing 1 (W/V) glucose, 0.2 (W/V) peptone (Difco), 0.1 (W/V) yeast extract (Difco), 0.1 (W/V) casamino acids (Difco) and 0.001 (V/V) vitamin solution [containing 0.01 (W/V) each of biotin, pyridoxin, thiamine, riboflavin, PABA and nicotinic acid (Sigma)]; and on 1 glucose minimal medium (GMM) with 10 mM NH4+ as sole nitrogen source (unless otherwise stated) and containing 0.52 g/l KCl, 0.52 g/l MgSO47H2O, 1.52 g/l KH2PO4, 0.001 (W/V) thiamine and 0.1 (W/V) trace elements (Fisher). CM supplements were added to GMM at the same concentrations as for CM. Amino acids and homocysteine (Sigma) were added to GMM as sole nitrogen sources at a final concentration of 10 mM.Nutrient Conditions during Rice InfectionFigure 6. Invasive hyphal growth but not appressorium formation, p.