Ethylene Promotes the Necrotic Lesion Formation and Basic PR Gene Expression in TMV-Infected Tobacco

Abstract

Ethylene has been thought to be an important factor for the induction of defense responses against pathogen attack, but its function in these responses has not been well denned. Here we show the direct involvement of ethylene in the formation of necrotic lesions and in basic pathogenesis-related (PR) protein gene induction in tobacco. Increase in ethylene production as well as accumulation of l-aminocyclopropane-l-carboxylic acid oxidase (ACO) gene transcript obviously preceded the lesion appearance in tobacco mosaic virus (TMV)-infected leaves in an N gene-dependent synchronous lesion formation system. Inhibitors of ethylene biosynthesis or action significantly suppressed both lesion formation and basic PR gene expression. Induction of these genes was enhanced in 1aminocyclopropane-1-carboxylic acid (ACC)-treated leaves especially in ACO-overexpressing transgenic tobacco plants. Further, we found that ethylene production during hypersensitive reaction is restricted at the level of ACO activity.

Involvement of ethylene in lesion development and systemic acquired resistance in tobacco during the hypersensitive reaction to tobacco mosaic virus

“…Under all conditions tested, inoculation with TMV led to the appearance of phenotypically normal local lesions, con®rming previous results [11,17,18] that the hypersensitive reaction of Samsun NN tobacco to TMV is not in¯uenced by altered ethylene production or perception. These results are at variance with those described recently by Ohtsubo et al [25] that ethylene is directly involved in the formation of necrotic lesions. However, those authors used a temperature-dependent accelerated lesion formation system in which detached tobacco leaves were shifted from 30 to 208C, whereas we employed intact plants maintained at about the latter temperature.…”

“…It could be argued that in this latter case the level of inhibition was insucient to reduce ethylene production at the site of lesion formation to a level comparable with that in healthy leaves. Indeed, contrasting ®ndings were described recently by Ohtsubo et al [25] indicating that the inhibitors of ethylene biosynthesis, AVG and cobalt chloride, as well as the inhibitor of ethylene action, 2,5-norbornadiene (NBD), signi®cantly suppressed lesion formation in Samsun NN tobacco after a shift from 30 to 208C. Moreover, lesion formation was accelerated in transgenic plants overexpressing the last enzyme in the ethylene biosynthetic pathway, ACO, upon application of ACC.…”

Loss of Function of FATTY ACID DESATURASE7 in Tomato Enhances Basal Aphid Resistance in a Salicylate-Dependent Manner

“…The proteinase inhibitor gene PI-II (GenBank gene identifier 543955) is transcriptionally activated in response to JAs and also ethylene (Farmer et al, 1992;Ohtsubo et al, 1999). Reverse transcription-quantitative PCR (RT-qPCR) was used to assess the effects of aphid feeding on the transcript abundance of P4 and PI-II in locally infested foliage of spr2 and wild-type tomato plants (cv Castlemart) 48 h after aphid inoculation.…”

Heterologous Expression of a Mutated Carnation Ethylene Receptor Gene, Dc-ETR1nr, Suppresses Petal Abscission and Autocatalytic Ethylene Production in Transgenic Torenia fournieri Lind.

“…Insertion of the etr1-1 gene under the control of the constitutive CaMV 35S promoter resulted in ethylene-insensitive plants with delayed flower senescence. However, such ethylene-insensitive plants have undesirable qualities, such as reduction in adventitious root formation, high levels of sensitivity to some pathogens, and reduced fruit set and fruit ripening (Clarke et al, 1999;Ohtsubo et al, 1999). Tissue-specific ethylene insensitivity will therefore be a better approach to conquering such problems.…”