Plant Molecular Biology 37: 445–454, 1998.
1998 Kluwer Academic Publishers. Printed in Belgium.
Differential expression of senescence-associated mRNAs during leaf
senescence induced by different senescence-inducing factors in Arabidopsis
, Sung Aeong Oh
, Young Hee Kim
, Hye Ryun Woo
and Hong Gil Nam
Department of Life Science and School of Environmental Engineering, Pohang University of Science and
Technology, Pohang, Kyungbuk, 790–784,South Korea (
author for correspondence);
Horticulture, Sangmyung Women’s University, Chonan, Chungnam, 330–180, South Korea;
Biology and BiotechnologyResearch Center, Jinju, Kyungnam, 660–701, South Korea
Received 27 June 1997; accepted in revised form 28 December 1997
Key words: age, Arabidopsis, cDNA, expression, leaf, senescence
Four cDNA clones, named pSEN2, pSEN3, pSEN4, and pSEN5, for mRNAs induced during leaf senescence
in Arabidopsis thaliana were characterized. The clones were isolated from a cDNA library of detached leaves
incubated in darkness for 2 days to accelerate senescence, ﬁrst by differential screening and then by examining
expression of the primarily screened clones during age-dependent leaf senescence. Transcript levels detected by
these cDNA clones, thus, were up-regulated in an age-dependentmanner and during dark-induced leaf senescence.
In contrast, when leaf senescence was induced by ethylene, ABA or methyl jasmonate, the transcript level detected
by the clones was differentially regulated depending on the senescence-inducinghormones. The transcript level for
pSEN4 increased during senescence induced by all three hormones, while the transcript detected by the pSEN2
clone did not increase during senescence induced by ethylene. The transcript level for pSEN5 was increased upon
ABA-induced senescence but decreased during ethylene-induced senescence. The pSEN3 clone detected multiple
transcriptsthat are differentiallyregulatedbythese factors. The results showthat, althoughthe apparent senescence
symptoms of Arabidopsis leaf appear similar regardless of the senescence-inducing factors, the detailed molecular
state of leaf cells during senescence induced by differentsenescence-inducingfactorsis different.ThepSEN3 clone
encodes a polyubiquitin and the pSEN4 clone encodes a peptide related to endoxyloglucan transferase. This result
is consistent with the expected roles of senescence-induced genes during leaf senescence.
Leaf senescence is the ﬁnal stage of leaf development,
leading to death of leaf cells. During this develop-
mental stage, leaf cells experience sequential disor-
ganization of cellular organellesand dramatic changes
of cellular metabolism [4, 25, 33, 37]. The metabolic
changes occurring during leaf senescence include loss
of photosynthetic activity and hydrolysis of macro-
molecules, such as proteins and lipids, built up during
the growth phase. This hydrolyticactivity is concomit-
The nucleotide sequence data reported will appear in the
EMBL, GenBank and DDBJ Nucleotide Sequence Databases under
the accession numbers AF035382 (pSEN2), AF035383 (pSEN3),
AF035384 (pSEN4) and AF035385 (pSEN5).
ant with massive mobilization of the hydrolyzed com-
pounds to the growing parts of plants such as young
leavesanddevelopingseeds[25, 33, 35, 37]. Thus,leaf
senescence, although deteriorative in nature, may be a
critical developmentalprocessfor ﬁtness of a plantand
now is regarded as an evolutionarily acquired process.
Due to the biological importance and potentials for
improvement of crop characteristics such as storage
life and plant productivity, quite extensive physiolo-
gical and biochemical studies have been conducted
on leaf senescence. In contrast, the molecular genetic
mechanismof leaf senescence is still largelyunknown.
Genetic and molecular studies of leaf senescence are
now providing supporting evidence for the notion that
leaf senescence is a genetically programmed event.