Plant Molecular Biology 34: 275–286, 1997.
1997 Kluwer Academic Publishers. Printed in Belgium.
Differential induction of seven 1-aminocyclopropane-1-carboxylate synthase
genes by elicitor in suspension cultures of tomato (Lycopersicon esculentum)
urg H. Oetiker
, David C. Olson, Oi Yin Shiu
and Shang Fa Yang
Department of Vegetable Crops, University of California at Davis, Davis, CA 95616, USA; present addresses:
Botanical Institute, University of Basel, Hebelstrasse 1, 4056 Basel, Switzerland (
author for correspondence);
Department of Botany, University of Hong Kong, Pokfulam Road, Hong Kong;
Institute of Botany, Academia
Sinica, Nankang, Taipei, Taiwan
Received 9 October 1996; accepted in revised form 25 February 1997
Key words: 1-aminocyclopropane-1-carboxylate (ACC) synthase, elicitor, ethylene, gene expression, tomato
The key enzyme of ethylene biosynthesis, ACC synthase, is encoded by a multigene family. We describe three new
DNA sequences encoding members of the ACC synthase family of the tomato. One of these sequences encodes a
novelACC synthase, LE-ACS6, which is phylogeneticallyrelated to the ACC synthases LE-ACS1A and LE-ACS1B.
Gene-speciﬁc probes for seven tomato ACC synthase genes were prepared. They were used for RNase protection
assays to study the accumulation of ACC synthase transcripts in suspension-cultured tomato cells after the addition
of an elicitor.
The ACC synthase genes LE-ACS2, LE-ACS5 and LE-ACS6 were strongly induced by the elicitor. In contrast,
the genes LE-ACS1B, LE-ACS3 and LE-ACS4 were constitutively expressed and LE-ACS1B was present at all times
at a particularly high level. Thus, there are two groups of ACC synthase transcripts expressed in these cells, either
elicitor-induced or constitutive. A transcript of LE-ACS1A was not detected. Despite the presence of LE-ACS1B,
LE-ACS2, LE-ACS3, LE-ACS4 and LE-ACS5, there was only little ethylene produced in the absence of the elicitor.
Increased ethylene production is usually correlated with the accumulation of ACC synthase transcripts, indicating
that ethylene production is controlled via the transcriptional activation of ACC synthase genes. However, the
abundance of several ACC synthase mRNAs studied was not strictly correlated with the rate of elicitor-induced
ethyleneproduction.Our data provide evidence that the activity of these ACC synthases may not solely be controlled
by the transcriptional activation of ACC synthase genes.
The plant hormone ethylene controls many aspects
of plant growth and development. Enhanced rates of
ethylene production are observed during germination,
ﬂower development, pollination, leaf and ﬂoral abscis-
sion and fruit ripening. Enhanced rates of ethylene pro-
duction are also observed when plants are subjected to
The nucleotidesequence data reportedwill appear in the EMBL,
GenBank and DDBJ Nucleotide Sequence Databases under the
accession numbers U74458 (active-site center from LE-ACS1A,
U74460 (pPCROR6, active-site center from LE-ACS1B); M38822,
the (LE-ACS5 active-site center from plasmid pBTAS3), U74461
(pPCROR2, active-site center from LE-ACS6); U74459, (pJO101A),
U75692, (pJO101B) and U74462 (pJO105).
various biotic or abiotic stresses, such as mechanic-
al strain, wounding, hypoxia and ﬂooding, chilling,
soil salinity and infection by pathogens [40, 41].
While the phenomenon of enhanced ethylene produc-
tion as a response to stresses has been observed many
times, the function of stress ethylene productionis elu-
sive [1, 6]. Ethylene is synthesized from S-adenosyl-
L-methionine via 1-aminocyclopropane-1-carboxylic
acid (ACC) . The rate limiting step in ethylene pro-
duction is ACC synthase (ACS), which is encoded by a
multigene family . In most cases, enhanced ethyl-
ene production rates appear correlated with enhanced
ACS transcription . However, transcription of ACS
genes may not be the only factor regulating the produc-
GR: 201001913, Pips nr. 135733 BIO2KAP
plan3710.tex; 7/05/1997; 13:43; v.7; p.1