Plant Molecular Biology 40: 455–465, 1999.
© 1999 Kluwer Academic Publishers. Printed in the Netherlands.
Rapid transcript accumulation of pathogenesis-related genes during an
incompatible interaction in bacterial speck disease-resistant tomato plants
Department of Agronomy, 1150 Lilly Hall of Life Sciences, Purdue University, West Lafayette, IN 47907-1150,
USA; present addresses:
Genetic Disease Resistance Group, Dupont Agricultural Products, P.O. Box 80402,
Wilmington, DE 19880-0402, USA;
Boyce Thompson Institute for Plant Research at Cornell University, Tower
Road, Ithaca, NY 14853-1801, USA (
author for correspondence)
Received 24 September 1998; accepted in revised form 22 February 1999
Key words: Lycopersicon esculentum, PR gene expression, Pto kinase, signal transduction
In the yeast two-hybrid system, the Pto kinase interacts with three putative transcription factors Pti4, Pti5 and Pti6.
The Pti4/5/6 proteins contain a DNA binding domain that recognizes and binds a DNA sequence (5
; the ‘PR box’) present in the promoter region of a large number of genes encoding ‘pathogenesis-related’ (PR)
proteins. We have now investigated the pathogen-induced expression of PR box-containing genes in tomato. We
isolated a tomato osmotin gene that contains two PR boxes in its promoter region and demonstrated that the
abundance of the osmotin transcript rapidly increases during an incompatible interaction involving Pto-containing
tomato plants and the bacterial pathogen Pseudomonassyringae pv. tomato expressing the avrPto gene. In addition,
we found that transcripts of two other tomato PR genes (encoding endochitinase and β-1,3-glucanase B) and at
least one ACC oxidase gene, all of which contain PR boxes in their promoter regions, rapidly accumulate in the
incompatible interaction. These data support the hypothesis that the tomato Pto kinase regulates the expression of
certain defense genes in tomato by interaction with transcription factors that bind the PR box.
Abbreviations: HR, hypersensitive response; PR, pathogenesis-related
Pathogenesis-related (PR) proteins were originally ob-
served to accumulate in tobacco plants in response to
TMV infection (van Loon and van Kammen, 1970).
Since then, several categoriesof PR proteinshave been
identiﬁed in tobacco as well as other plant species
(Linthorst, 1991). Expression of PR genes is now
known to be a common defense response to pathogen
invasion in many plant species (Linthorst, 1991). PR
proteins are deﬁned as plant proteins that are induced
in pathological or related situations. ‘Pathological sit-
uations’ refers to all types of infected states such as
during a resistance, hypersensitive, or susceptible re-
The nucleotide sequence data reported will appear in the
EMBL, GenBank and DDBJ Nucleotide Sequence Databases under
the accession number AF093743.
sponse, parasitic attack by nematodes, and attack by
phytophagous insects and herbivores. ‘Related situa-
tions’ refers to wounding as well as the application of
chemicals (e.g. elicitors, salicylic acid) that mimic the
effect of pathogen infection by inducing some aspects
of the host response (van Loon et al., 1994).
Several promoter elements have been identiﬁed
that are involved in PR gene expression upon wound-
ing, or exposure to ethylene, methyl jasmonate, sali-
cylic acid, or other elicitors (Goldsbrough and Cullis,
1981; Ohl et al., 1990; Palm et al., 1990; Gurley and
Key, 1991; Mason et al., 1993; Matton et al., 1993;
Sutliff et al., 1993). In particular, the cis element 5
(also termed the PR box or GCC box)
is found in many plant defense-related gene promot-
ers, including the promoters of many basic PR proteins
(see Zhou et al. (1997) for a compilation of these