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A calcium-dependent protein kinase at the plasma membrane prevents membrane lipid peroxidation and confers tolerance to salt and drought stress in rice plants.
The
OsCPK4
gene is a member of the complex gene family of calcium-dependent protein kinases in rice (
Oryza sativa
). Here, we report that
OsCPK4
expression is induced by high salinity, drought, and the phytohormone abscisic acid. Moreover, a plasma membrane localization of OsCPK4 was observed by transient expression assays of green fluorescent protein-tagged OsCPK4 in onion (
Allium cepa
) epidermal cells. Overexpression of
OsCPK4
in rice plants significantly enhances tolerance to salt and drought stress. Knockdown rice plants, however, are severely impaired in growth and development. Compared with control plants,
OsCPK4
overexpressor plants exhibit stronger water-holding capability and reduced levels of membrane lipid peroxidation and electrolyte leakage under drought or salt stress conditions. Also, salt-treated
OsCPK4
seedlings accumulate less Na
+
in their roots. We carried out microarray analysis of transgenic rice overexpressing
OsCPK4
and found that overexpression of
OsCPK4
has a low impact on the rice transcriptome. Moreover, no genes were found to be commonly regulated by
OsCPK4
in roots and leaves of rice plants. A significant number of genes involved in lipid metabolism and protection against oxidative stress appear to be up-regulated by
OsCPK4
in roots of overexpressor plants. Meanwhile,
OsCPK4
overexpression has no effect on the expression of well-characterized abiotic stress-associated transcriptional regulatory networks (i.e.
ORYZA SATIVA DEHYDRATION-RESPONSIVE ELEMENT BINDING PROTEIN1
and
ORYZA SATIVA No Apical Meristem, Arabidopsis Transcription Activation Factor1-2, Cup-Shaped Cotyledon6
genes) and
LATE EMBRYOGENESIS ABUNDANT
genes in their roots. Taken together, our data show that
OsCPK4
functions as a positive regulator of the salt and drought stress responses in rice via the protection of cellular membranes from stress-induced oxidative damage.