Plant Molecular Biology 46: 313–323, 2001.
© 2001 Kluwer Academic Publishers. Printed in the Netherlands.
Inducible expression of bacterio-opsin in transgenic tobacco and tomato
Ludmila Rizhsky and Ron Mittler
Department of Plant Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
Department of Biology, Technion-Israel Institute of Technology, Technion City. Haifa 32 000, Israel (
correspondence: fax 972-2-6585093, e-mail: email@example.com)
Received 12 August 2000; accepted in revised form 28 February 2001
Key words: bacterio-opsin (bO), biotechnology, lesion mimic, plant-pathogen interactions, proteinase inhibitor 2
(Pin2), wound response
The development of new strategies to enhance resistance of plants to pathogens is instrumental in preventing
agricultural losses. Lesion mimic, the spontaneous formation of lesions resembling hypersensitive response lesions
in the absence of a pathogen, is a dramatic phenotype occasionally induced upon expression of certain transgenes
in plants. These transgenes simulate the 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 these
genes in plants is associated with the spontaneous formation of lesions on leaves and stems, reduced growth, and
lower yield. We tested the possibility of using a wound-inducible promoter to control the expression of bacterio-
opsin (bO), a transgene that confers a lesion mimic phenotype in tobacco and tomato plants when constitutively
expressed. We found that plants with inducible expression of bO did not develop spontaneous lesions. Nevertheless,
under controlled laboratory conditions, they were found to be resistant to infection by pathogens. The activation
of defense mechanisms by the bO gene was not constitutive, and occurred in response to wounding or pathogen
infection. Furthermore, wounding of transgenic tobacco plants resulted in the induction of systemic resistance to
pathogen attack within 48 h. Our ﬁndings provide a promising initial assessment for the use of wound-inducible
promoters as a new strategy to enhance pathogen resistance in transgenic crops by means of lesion mimic genes.
Abbreviations: bO, bacterio-opsin; MJ, methyl jasmonate; Nos, nopaline synthase; Pin2, proteinase inhibitor 2; PR,
pathogenesis-related; SA, salicylic acid; SAR, systemic acquired resistance; TMV, tobacco mosaic virus; TMVcp,
TMV coat protein; TNV, tobacco necrosis virus; WT, wild type; 18S, 18S rRNA; 35S, CaMV 35S promoter.
Each year pathogens such as viruses, bacteria, or fungi
cause extensive losses in agricultural production. Al-
though plants contain a variety of defense mechanisms
that prevent infection by most pathogens, infected
plants are sometimes incapable of recognizing the in-
vading pathogen and consequently do not mount a
defense response. Alternatively, the defense response
is mobilized at a slow rate that is insufﬁcient to re-
strict pathogen spread (Goodman and Novacky, 1994;
Hammond-Kosack and Jones, 1996).
Recognition of an invading pathogen by the plant
activates a signal transduction pathway resulting in
the induction of many plant defense mechanisms.
These include the accumulation of salicylic acid (SA),
synthesis of pathogenesis-related (PR) proteins that
exhibit antimicrobial activity such as glucanases and
chitinases, thickening and hardening of cell walls, and
an increased production of antimicrobial compounds
called phytoalexins (Yang et al., 1997). These de-