Induction of pathogenesis-related genes and pathogen resistance in tobacco by fungal elicitors and plant growth regulators
Abstract
Salicylic acid, methyl-jasmonate and ethylene have been suggested as signals for activation of plant defense responses against pathogen infections. Fungal elicitors have been shown to induce defense-related genes. However, it is not known how pathogenesis-related (PR) genes are regulated by fungal elicitors. Arachidonic acid (AA) and cellulases, which are fungal elicitors, have been used to study the induction of osmotin gene expression. The combination of AA and cellulases resulted in more than an additive effect of AA and cellulases alone on activating the osmotin gene. Inhibitor studies suggested that ethylene is involved in the induction of osmotin by these two elicitors. Heat-released elicitors from mycelial walls of pathogenic (Phytophthora parasitica var. nicotianae, race 0) and non-pathogenic (Trichoderma longibrachiatum) fungi have been isolated and used to induce PR-1 and osmotin genes by these elicitors. The non-pathogenic elicitor induced PR gene expression to a much higher level than did the pathogenic elicitor. The expression patterns of these two PR genes and the accumulations of their encoded proteins were dramatically affected by salicylic acid, methyl-jasmonate, and ethylene and combinations of these plant growth regulators. Ethylene, jasmonate, and salicylic acid are involved in the induction of PR-1 and osmotin by mycelial wall elicitor of non-pathogenic fungus. The non-pathogenic elicitor, but not the pathogenic elicitor, induced resistance of tobacco seedlings to P. parasitica var. nicotianae (race 0), a pathogen which causes black shank disease in tobacco. The protection induced by the non-pathogenic elicitor was dramatic and lasted for more than 3 weeks compared to salicylic acid or the combination of salicylic acid and methyl-jasmonate which could only induce resistance for a few days.
Degree
Ph.D.
Advisors
Bressan, Purdue University.
Subject Area
Botany|Molecular biology|Plant pathology
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