Plant Molecular Biology 35: 847–854, 1997.
1997 Kluwer Academic Publishers. Printed in Belgium.
ER5, a tomato cDNA encoding an ethylene-responsive LEA-like protein:
characterization and expression in response to drought, ABA and wounding
Hicham Zegzouti, Brian Jones, Christel Marty, Jean-Marc Leli
evre, Alain Latch
Jean-Claude Pech and Mondher Bouzayen
Ecole Nationale Sup
erieure Agronomique de Toulouse, UA-INRA, 145, Avenue de Muret, 31076 Toulouse Cedex,
author for correspondence)
Received 23 December 1996; accepted in revised form 24 July 1997
Key words: differentialdisplay, droughtstress, ethyleneinducible, LEAprotein,Lycopersiconesculentum,RT-PCR
We report the isolation by differential display of a novel tomato ethylene-responsive cDNA, designated ER5.
RT-PCR analysis of ER5 expression revealed an early (15 min) and transient induction by ethylene in tomato fruit,
leaves and roots. ER5 mRNA accumulated during 2 h of ethylene treatment and thereafter underwent a dramatic
decline leading to undetectable expression after 5 h of treatment. The full-length cDNA clone of 748 bp was
obtained and DNA sequence analysis showed strong homologies to members of the atypical hydrophobic group of
theLEA proteinfamily. Thepredicted aminoacid sequenceshows67%, 64%, 64%, and61% sequenceidentity with
the tomato Lemmi9, soybean D95-4, cotton Lea14-A, and resurrection plant pcC27-45 gene products, respectively.
As with the other members of this group, ER5 encodes a predominantly hydrophobic protein. Prolonged drought
stress stimulates ER5 expression in leaves and roots, while ABA induction of this ethylene-responsive clone is
conﬁned to the leaves. The use of 1-MCP, an inhibitor of ethylene action, indicates that the drought induction of
ER5 is ethylene-mediated in tomato roots. Finally, wounding stimulates ER5 mRNA accumulation in leaves and
roots. Among the Lea gene family this novel clone is the ﬁrst to display an ethylene-regulated expression.
Lea (late embryogenesis-abundant) genes encode a
diverse group of putative desiccation protectant pro-
teins that are induced during the post-abscission stage
of late embryo development . Lea and lea-like
genes have also been isolated from vegetative tissues
and areinduced by water stress, as well as osmotic and
low-temperature stress [6, 28]. Most members of this
extensive group of genes are responsive to exogenous
ABA, a phytohormone whose levels increase during
water stress [7, 8].
there is an atypical group of LEA proteins that contain
an abundance of hydrophobic domains. The soybean
D95-4 , cotton Lea14-A, tomato Lemmi9 
Thenucleotidesequencedatareportedwill appear in theEMBL,
GenBank and DDBJ Nucleotide Sequence Databases under the
accession number U77719.
among this group. All but the tomato Lemmi9 encode
proteins that are induced by both drought and ABA
treatment. It has been speculated that the function of
these highly homologousproteins may differfrom that
of the hydrophilic LEA proteins .
In higher plants, ethylene plays a critical role in a
numberof physiologicalprocessesboth during normal
developmentand in response to environmentalchange
[for review, see 30]. The identiﬁcation of ethylene-
regulatedgenes is importantfor understandingthe role
of ethylene in these processes. We recently initiated a
projectaimed at isolating ethylene-responsivegenes in
tomato fruit using a sensitive new approach, suitable
for the isolation of weakly expressed genes, known as
mRNA differentialdisplay[19, 20, 31]. To date, sever-
al ethylene-regulatedcDNA clones have beenisolated.
In this paper we describe the isolation and charac-
terization of ER5, a novel tomato ethylene-regulated