A comparison of in vivo targeted gene expression during fungal colonization of DED‐susceptible Ulmus americana

Abstract

SummaryThis study examined in vivo gene expression associated with the colonization of Dutch elm disease‐susceptible Ulmus americana by H175, an aggressive strain of Ophiostoma novo‐ulmi Brasier. Stress‐related genes encoding phenylalanine ammonia‐lyase (PAL), chitinase (CHT) and polygalacturonase inhibiting protein (PGIP) were used to observe gene expression changes during U. americana colonization by H175. A novel non‐invasive method employing leaf midribs was used to observe plant gene expression, fungal colonization and mansonone F accumulation. RNA dot blots determined that all transcripts probed were induced during colonization compared with unchallenged controls. PAL and PGIP expression were increased in leaf midrib tissue prior to fungal colonization, suggesting a remote signal induction. CHT expression was increased locally with the presence of fungus, suggesting a local signal induction. Mansonone F accumulation was detected prior to fungal colonization suggesting a remote signal induction. The in vivo method used will provide a useful tool for in vivo disease research, particularly in trees, where chemically complex tissue can impede RNA isolation and downstream analysis.