Plant Molecular Biology 36: 935–939, 1998.
1998 Kluwer Academic Publishers. Printed in Belgium.
Isolation and characterization of a heat-induced gene, hcit2,encodinga
novel 16.5 kDa protein: expression coincides with heat-induced tolerance to
, Lurie Susan
& David Weiss
Kennedy-Leigh Centre for Horticultural Research, Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100
author for correspondence);
Department of Postharvest Science, Agricultural Research Organization,
The Volcani Center, Bet Dagan 50250, Israel
Received 12 August 1997; accepted in revised form 8 December 1997
Key words: chilling injury, heat-shock proteins, low temperature, Lycopersicon esculentum, tomato fruits
Heat treatment of tomato fruits induces tolerance to chilling injury. We have previously shown that speciﬁc heat-
shock proteins(HSPs)areexpressedin heated tomato fruits after cold storage. To search forheat-induced genesthat
are expressed at lowtemperatures, a cDNA library prepared from pre-heated chilled tomato fruits was differentially
screened. A novel cDNA clone, hcit2, encoding a protein of ca. 16.5 kDa, was isolated. The predicted protein
contains three putative trans-membranehydrophobicsequences, suggesting that the protein is membrane-localized.
Theexpressionof hcit2 in fruits was inducedby high temperature, butnot by other stresses such as lowtemperature,
drought or anaerobic conditions, and not during fruit ripening. A high level of hcit2 transcript was found in heated
fruits after 2 weeks at 2
C. High temperatures also induced hcit2 expression in tomato leaves, ﬂowers and stems.
The HCIT2 protein may be involved in the acquisition of tolerance to chilling injury.
Higher plants, being immobile, have a greater need to
protect themselves against transient stresses, such as
high or low temperatures, which dramatically affect
their survival and productivity. All organisms respond
to high temperatures by inducing the synthesis of a
small group of evolutionarily conserved polypeptides
known as heat-shock proteins (HSPs). Some plant
help cells withstand the toxic effects of extreme tem-
peratures . Recently, molecular chaperone activity
of both plant and mammalian HSPs and the related
-crystallin protein of the vertebrate eye lens has been
demonstrated in vitro [13, 25].
Several studies have shown the existence of cross-
tolerance, whereby the exposureof a plant to moderate
Thenucleotidesequencedatareportedwillappear in theEMBL,
GenBank and DDBJ Nucleotide Sequence Databases under the
accession number U67131.
stress conditions induces tolerance to other kinds of
stresses as well [19, 23]. High-temperature stress has
been found to protect a number of fruits and veget-
ables, including tomato, against chilling injury [20,
4, 14, 17]. We have previously shown that mature
green tomato fruits, kept at 38
C, can later sustain a
temperature of 2
C for several weeks without devel-
oping symptoms of chilling injury . These fruits
then ripen normally under ambient temperature condi-
chilling-injurysymptomsanddo not ripenunder ambi-
atures inducethe synthesisof small HSPs (smHSPs) in
the fruits . These newly synthesized smHSPs were
also foundin heated fruits that were transferred to 2
and stored for 3 weeks. Plants synthesize numerous
smHSPs, ranging in size from 15 to 30 kDa. These
proteins are related to smHSPs of other organisms and
-crystallin proteins of the vertebrate eye lens