Plant Molecular Biology 33: 169–174, 1997.
1997 Kluwer Academic Publishers. Printed in Belgium.
Cloning and expression analysis of a gene that shows developmental
regulation upon tuberization in potato
, Jordi Gasc
on, Esther Carrera, Elena Monte and Salom
Centro de Investigacion y Desarrollo, C.S.I.C., Jordi Girona 18–26, E-08034 Barcelona, Spain (
Present address: Horticulture Research International, Wellesbourne, Warwick, CV35 9EF, UK
Received 21 March 1996; accepted in revised form 23 September 1996
Key words: fruit ripening, potato, tomato, tuberization
Differential screening of a potato leaf cDNA library with cDNA probes made from tuberizing and non-tuberizing
Solanum demissum plants led to the identiﬁcation of a clone that is upregulated in leaves and other tissues upon
tuberization. This clone was also shown to have a high level of expression in green tomato fruit, its expression
falling off as the fruit turns red. No sucrose or hormonal regulation of the expression of this clone was observed
and it did not respond to wounding or heat stress. Clone 32B is 532 bp long and contains an open reading frame
encoding a small protein of 98 amino acids. The deduced protein sequence has a putative signal peptide for ER
transport and a 10 amino acid domain in the C-terminal region of the protein, both of which are also found in the
cotton LEA5, Arabidopsis Di21 and the mungbean Arg2 proteins.
Many physiological changes occur in the potato
plant upon tuberization apart from the swelling of
the stolon tip to form a new storage organ, the tuber.
Leaves, for example, become larger, broader and grow
and thicker, and there is an increased leaf-to-stem dry
weight ratio, increased ﬂower bud abortion and accel-
erated senescence [reviewed in 14]. Many of these
changes may be explained by a shift in the partition-
ing of photoassimilates from above-ground vegetative
growth towards development of the tubers .
Therehave been severalreportsdescribingchanges
in gene expression that occur during tuberization [13,
15, 16]. The accumulation of proteins involved in the
storage of nitrogen, such as patatin, and in the storage
ADP-glucose pyrophosphorylase, have been shown to
occur upon tuberization [reviewed in 13]. Changes in
polyamine biosynthesis have also been reported .
The majority of these changes, however, take place in
Thenucleotidesequencedata reportedwill appear inthe EMBL,
GenBank and DDBJ Nucleotide Sequence Databases under the
accession number X98304.
the stolon tip or in the developing tuber. We have pre-
viously described a clone that shows increased levels
of expressionin the leaves of potato plants upon tuber-
ization . This gene was later identiﬁed through
sequence homology as a potato DnaJ homologue, and
thus may play a role in protein folding, transport or
compartmentalization. In this paper we describe the
isolation, sequence and expression analysis of another
gene that has been isolated on the basis of its increased
expression in leaves of tuberizing potato plants.
Isolation of induced clone
A cDNA library was constructed from poly(A)
RNAfrom tuberizingSolanumdemissumpotato plants
grown in short day conditions (8 h light, 16 h dark).
50000 clones from this library were differentially
plants grown in short days, or non-induced plants
grown in short day plus night-break conditions. The
only difference in the conditions in which the two sets
ofplantsweregrownwasthe 30min nightbreak, given
in the middle of the dark period to one set of plants,