Inducible expression of bacterio-opsin in transgenic tobacco and tomato plants

The development of new strategies to enhance resistance of plants to pathog ens is instrumental in preventing agricultural losses. Lesion mimic, the sp ontaneous formation of lesions resembling hypersensitive response lesions i n the absence of a pathogen, is a dramatic phenotype occasionally induced u pon expression of certain transgenes in plants. These transgenes simulate t he presence of a pathogen and, therefore, activate the plant anti-pathogen defense mechanisms and induce a state of systemic resistance. Lesion mimic genes have been successfully used to enhance the resistance of a number of different plants to pathogen attack. However, constitutive expression of th ese genes in plants is associated with the spontaneous formation of lesions on leaves and stems, reduced growth, and lower yield. We tested the possib ility of using a wound-inducible promoter to control the expression of bact erio-opsin (bO), a transgene that confers a lesion mimic phenotype in tobac co and tomato plants when constitutively expressed. We found that plants wi th inducible expression of bO did not develop spontaneous lesions. Neverthe less, under controlled laboratory conditions, they were found to be resista nt to infection by pathogens. The activation of defense mechanisms by the b O gene was not constitutive, and occurred in response to wounding or pathog en infection. Furthermore, wounding of transgenic tobacco plants resulted i n the induction of systemic resistance to pathogen attack within 48 h. Our findings provide a promising initial assessment for the use of wound-induci ble promoters as a new strategy to enhance pathogen resistance in transgeni c crops by means of lesion mimic genes.