Defense activation and enhanced pathogen tolerance induced by H2O2 in transgenic tobacco

AUTOR(ES)

Chamnongpol, Sangpen

FONTE

The National Academy of Sciences

RESUMO

Transgenic tobacco deficient in the H2O2-removing enzyme catalase (Cat1AS) was used as an inducible and noninvasive system to study the role of H2O2 as an activator of pathogenesis-related (PR) proteins in plants. Excess H2O2 in Cat1AS plants was generated by simply increasing light intensities. Sustained exposure of Cat1AS plants to excess H2O2 provoked tissue damage, stimulated salicylic acid and ethylene production, and induced the expression of acidic and basic PR proteins with a timing and magnitude similar to the hypersensitive response against pathogens. Salicylic acid production was biphasic, and the first peak of salicylic acid as well as the peak of ethylene occurred within the first hours of high light, which is long before the development of tissue necrosis. Under these conditions, accumulation of acidic PR proteins was also seen in upper leaves that were not exposed to high light, indicating systemic induction of expression. Short exposure of Cat1AS plants to excess H2O2 did not cause damage, induced local expression of acidic and basic PR proteins, and enhanced pathogen tolerance. However, the timing and magnitude of PR protein induction was in this case more similar to that in upper uninfected leaves than to that in hypersensitive-response leaves of pathogen-infected plants. Together, these data demonstrate that sublethal levels of H2O2 activate expression of acidic and basic PR proteins and lead to enhanced pathogen tolerance. However, rapid and strong activation of PR protein expression, as seen during the hypersensitive response, occurs only when excess H2O2 is accompanied by leaf necrosis.

Documentos Relacionados

• Activation of Host Defense Mechanisms by Elevated Production of H2O2 in Transgenic Plants.
• Enhanced salt tolerance in maize plants induced by H2O2 leaf spraying is associated with improved gas exchange rather than with non-enzymatic antioxidant system
• Competence for Elicitation of H2O2 in Hypocotyls of Cucumber Is Induced by Breaching the Cuticle and Is Enhanced by Salicylic Acid.
• Activation of flavin-containing oxidases underlies light-induced production of H2O2 in mammalian cells
• Activation of protein kinase C by tyrosine phosphorylation in response to H2O2