Pathogen-Induced Elicitin Production in Transgenic Tobacco Generates a Hypersensitive Response and Nonspecific Disease Resistance

Abstract

The rapid and effective activation of disease resistance responses is essential for plant defense against pathogen attack. These responses are initiated when pathogen-derived molecules (elicitors) are recognized by the host. We have developed a strategy for creating novel disease resistance traits whereby transgenic plants respond to infection by a virulent pathogen with the production of an elicitor. To this end, we generated transgenic tobacco plants harboring a fusion between the pathogen-inducible tobacco hsr 203J gene promoter and a Phytophthora cryptogea gene encoding the highly active elicitor cryptogein. Under noninduced conditions, the transgene was silent, and no cryptogein could be detected in the transgenic plants. In contrast, infection by the virulent fungus P. parasitica var nicotianae stimulated cryptogein production that coincided with the fast induction of several defense genes at and around the infection sites. Induced elicitor production resulted in a localized necrosis that resembled a P. cryptogea-induced hypersensitive response and that restricted further growth of the pathogen. The transgenic plants displayed enhanced resistance to fungal pathogens that were unrelated to Phytophthora species, such as Thielaviopsis basicola, Erysiphe cichoracearum, and Botrytis cinerea. Thus, broad-spectrum disease resistance of a plant can be generated without the constitutive synthesis of a transgene product.

Expression of the Hypersensitive Response-assisting Protein in Arabidopsis Results in Harpin-dependent Hypersensitive Cell Death in Response to Erwinia carotovora

“…Introduction of foreign genes of nonplant origin to target plants are capable of protecting plant from bacterial pathogen infection through antibacterial genes or hypersensitivity cell death (HCD) associated genes (Keller et al, 1999;Shen et al, 2000;Verberne et al, 2000). For example, over-expression of R2R3 MYB-related gene or AtMYB30 leads to the induction of HCD and could resist pathogen attack (Vailleau et al, 2002).…”

Are elicitins cryptograms in plant-Oomycete communications?

“…This resistance was not clear, since the inoculated plants were almost ruined by the pathogen, and the protection was estimated as the number of leaves on axillary shoots emerging from the low, still living stump of stems. The second strategy [145] was to control foreign gene expression and to address the protein to the apoplastic space, which allowed the elicitin to bind to its putative receptor located on the outer plasma membrane [126]. Controlling gene expression is a guarantee for limiting cell death in the appropriate area where plant and pathogen interact.…”

The hrpN gene of Erwinia amylovora stimulates tobacco growth and enhances resistance to Botrytis cinerea

“…However, activation of defense-signaling cascades in plants is a consequence of sensing of the elicitor by specific plant receptors (Tripathy et al 2003). Since harpin-induced HR is a potentially useful tool for conferring pathogen-resistance on selected plants, transformation with harp genes has been used to engineer pathogen-resistance (Keller et al 1999;Peng et al 2004). Here, we report that transgenic tobacco plants expressing hrpN not only had the expected enhanced pathogen-resistance, but also showed accelerated growth and development.…”