Figure 4.
The meaB‐related nitrogen growth phenotype, but not the virulence phenotype of revertant 6G5, is linked to insertion of the imp160::gfp element. (A) Assay for repression of nitrate reductase activity by ammonium. The indicated strains were grown for 3 days on minimal medium containing 10 mm ammonium plus 100 mm chlorate. Wild‐type hyphal growth under these conditions requires meaB‐mediated repression of nitrate reductase activity, whereas derepression results in chlorate toxicity. (B) Infection assay on tomato plants. Groups of 10 plants were inoculated by immersing the roots into a suspension of 5 × 106 freshly obtained microconidia/mL of the indicated strains. The severity of disease symptoms was recorded at different times after inoculation, using an index ranging from 1 (healthy plant) to 5 (dead plant). wt, wild‐type.