OsCDPK13, a calcium-dependent protein kinase gene from rice,
is induced by cold and gibberellin in rice leaf sheath
Fida Abbasi, Haruko Onodera, Seiichi Toki, Hiroshi Tanaka and Setsuko Komatsu*
National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan (*author for correspondence; e-mail
skomatsu@affrc.go.jp)
Received 1 May 2004; accepted in revised form 7 July 2004
Key words: cold, gibberellin, leaf sheath, OsCDPK13, rice
Abstract
Calcium-dependent protein kinases (CDPKs) play an important role in rice signal transduction, but the
precise role of each individual CDPK is still largely unknown. Recently, a full-length cDNA encoding
OsCDPK13 from rice seedling was isolated. To characterize the function of OsCDPK13, its responses to
various stresses and hormones were analyzed in this study. OsCDPK13 accumulated in 2-week-old leaf
sheath and callus, and became phosphorylated in response to cold and gibberellin (GA). OsCDPK13 gene
expression and protein accumulation were up-regulated in response to GA
3
treatment, but suppressed in
response to abscisic acid and brassinolide. Antisense OsCDPK13 transgenic rice lines were shorter than the
vector control lines, and the expression of OsCDPK13 was lower in dwarf mutants of rice than in wild type.
Furthermore, OsCDPK13 gene expression and protein accumulation were enhanced in response to cold,
but suppressed under salt and drought stresses. Sense OsCDPK13 transgenic rice lines had higher recovery
rates after cold stress than vector control rice. The expression of OsCDPK13 was stronger in cold-tolerant
rice varieties than in cold-sensitive ones. The results suggest that OsCDPK13 might be an important
signaling component in the response of rice to GA and cold stress.
Introduction
Calcium is a ubiquitous signal molecule and chan-
ges in cytosolic Ca
2+
concentration are involved in
plant responses to various stimuli, including light,
environmental stresses, pathogen attack, and hor-
mones (Pooviah and Reddy, 1993; Bush, 1995).
Calcium acts through various intracellular media-
tors, including calmodulin (CaM) and Ca
2+
-regu-
lated kinases (Sopory and Munshi, 1998). Plants
contain a novel group of kinases, designated as
Ca
2+
-dependent protein kinases (CDPKs; EC
2.7.1.37), which are found only in plants, green
algae, and protozoa (Hrabak, 2003). CDPKs are
biochemically distinct from other Ca
2+
-dependent
kinases, such as Ca
2+
-and phospholipid-dependent
protein kinases and Ca
2+
/CaM-dependent protein
kinases, because they are activated by direct binding
of Ca
2+
-and are independent of CaM (Harmon
et al., 1987; Batty and Venis, 1988).
The CDPK family is represented by many genes,
with 12 subfamilies comprising 34 isoforms in
Arabidopsis and 27 in rice (Harper et al., 2004).
Some of the Ca
2+
-regulated kinases also show
potential for regulation by lipid signals and kinase
cascades. Thus, Ca
2+
- regulated kinases provide
potential nodes of cross talk between multiple
signaling pathways that integrate Ca
2+
signals
into all aspects of plant growth and development
(Harper et al., 2004). This large number of genes
suggests that individual isoforms have different
functions and participate in multiple, distinct sig-
naling pathways (Romeis et al., 2001). Indeed, when
Arabidopsis CDPKs were transiently expressed
in maize leaf protoplasts, only two of the eight
AtCDPK isoforms induced expression from the
Plant Molecular Biology 55: 541–552, 2004.
Ó 2004 Kluwer Academic Publishers. Printed in the Netherlands.
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