Ectopic overexpression of tomato JERF3 in tobacco activates
downstream gene expression and enhances salt tolerance
, Zejun Huang
, Qi Chen, Zhijin Zhang, Hongbo Zhang, Yanming Wu,
Dafang Huang and Rongfeng Huang*
The National Plant Gene Research Center (Beijing), Biotechnology Research Institute, Chinese Academy of
Agricultural Sciences, Beijing 100081, China (*author for correspondence; e-mail rongfeng@public3.
These authors contributed equally to this work.
Received 14 January 2004; accepted in revised form 5 April 2004
Key words: DRE, ERF proteins, GCC box, JERF3, PR gene expression, salt tolerance
The ethylene, jasmonic acid and osmotic signaling pathways respond to environmental stimuli and in order
to understand how plants adapt to biotic and abiotic stresses it is important to understand how these
pathways interact each other. In this paper, we report a novel ERF protein – jasmonate and ethylene-
responsive factor 3 (JERF3) – that unites these pathways. JERF3, which functions as an in vivo tran-
scription activator in yeast, binds to the GCC box, an element responsive to ethylene/JA signaling, as well
as to DRE, a dehydration-responsive element that responds to dehydration, high salt and low-temperature.
Expression of JERF3 in tomato is mainly induced by ethylene, JA, cold, salt or ABA. Constitutive
expression of JERF3 in transgenic tobacco signiﬁcantly activated expression of pathogenesis-related genes
that contained the GCC box, resulting in enhanced tolerance to salt. These results indicate that JERF3
functions as a linker in ethylene- and osmotic stress-signaling pathways.
Adverse environmental conditions such as
drought, high salt, extreme temperatures and
pathogen attack greatly impair crop productivity.
Since plants cannot move to avoid stressful con-
ditions, they must employ alternative ways to
withstand stress by activating multiple defense
mechanisms through expressing speciﬁc genes and
synthesizing a large number of stress proteins that
play distinct and important role in stress response
and plant defense (Skriver and Mundy, 1990;
Reymond and Farmer, 1998; Demekamp and
Smeekens, 2003). Accumulating evidences dem-
onstrated that stress responses of plants are regu-
lated by multiple signaling pathways, for example,
salicylic acid (SA), ethylene, jasmonic acid (JA)
and abscisic acid (ABA) have been shown to be
important components of defense response path-
ways (Dong, 1998; Reymond and Farmer, 1998;
Dempsey et al., 1999; Pieterse and van Loon, 1999;
Xiong et al., 2002), but the communication among
these plant hormone signaling pathways is not well
understood. Ethylene is an important endogenous
plant hormone that aﬀects virtually many aspects
of plant growth and development and also par-
ticipates in kinds of stress responses, such as seed
germination, cell fate, fruit ripening, senescence
and infection by pathogens. In response to stres-
ses, ethylene induces the expression of certain de-
fence genes. Exogenous application of ethylene
induces accumulation of class I basic chitinases,
class I basic b-glucanase and other basic-type
pathogenesis-related (PR) proteins (Boller et al.,
1983; Felix and Meins, 1987). Through analysis of
PR gene promoter, an 11 bp ethylene-responsive
element TAAGAGCCGCC which has been re-
ferred to as the GCC box (Ohme-Takagi and
Plant Molecular Biology 55: 183–192, 2004.
Ó 2004 Kluwer Academic Publishers. Printed in the Netherlands.