Researchers have identified the effects of pyriculol on rice's defense against Magnaporthe oryzae. The study indicates no correlation between levels of the metabolite and disease severity. External application of pyriculol or its isomer pyriculariol reduced lesion expansion by 30 percent.
Rice blast affects rice crops in more than 85 countries. The disease also affects other cereals. It spreads rapidly. In just a few days, extensive areas of dead leaves can appear, and grain production drops.
The study evaluated transgenic strains of the fungus with alterations in pyriculol biosynthesis. Pathogenicity assays involved different rice genotypes. The results did not indicate pyriculol as a virulence factor of Magnaporthe oryzae.
According to the study, pyriculol mimics part of the action of salicylic acid, a compound associated with plant defense. The metabolite suppressed early genes in jasmonate biosynthesis, such as OsAOS1, OsAOS2, and OsAOC. It also affected wound-responsive JAZ transcripts.
The molecule preserved the expression of OsJAR1. This effect allowed the systemic conversion of methyl jasmonate to JA-Ile. Thus, pyriculol modulated the interaction between salicylic acid and jasmonate. The process favored the preparation of the defense associated with salicylic acid and maintained systemic signaling by jasmonate.
Histological analyses indicated pyriculol-induced cell death in the host tissue. This response restricted the advancement of fungal hyphae. The effect acted in conjunction with the biosynthesis of phytoalexins triggered by the pathogen.
Further information can be found at doi.org/10.1093/jxb/erag061
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