Overexpression of the mitogen-activated protein kinase gene OsMAPK33 enhances sensitivity to salt stress in rice (Oryza sativa L.).
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2011-03
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Abstract
Mitogen-activated protein kinases (MAPK) signalling cascades are activated by extracellular stimuli such as environmental
stresses and pathogens in higher eukaryotic plants. To know more about MAPK signalling in plants, aMAPK cDNA clone,
OsMAPK33, was isolated from rice. The gene is mainly induced by drought stress. In phylogenetic analysis, OsMAPK33
(Os02g0148100) showed approximately 47–93% identity at the amino acid level with other plant MAPKs. It was found
to exhibit organ-specific expression with relatively higher expression in leaves as compared with roots or stems, and to
exist as a single copy in the rice genome. To investigate the biological functions of OsMAPK33 in rice MAPK signalling,
transgenic rice plants that either overexpressed or suppressed OsMAPK33 were made. Under dehydration conditions, the
suppressed lines showed lower osmotic potential compared with that of wild-type plants, suggesting a role of OsMAPK33
in osmotic homeostasis. Nonetheless, the suppressed lines did not display any significant difference in drought tolerance
compared with their wild-type plants. With increased salinity, there was still no difference in salt tolerance between
OsMAPK33-suppressed lines and their wild-type plants. However, the overexpressing lines showed greater reduction in
biomass accumulation and higher sodium uptake into cells, resulting in a lower K+/Na+ ratio inside the cell than that in the
wild-type plants and OsMAPK33-suppressed lines. These results suggest that OsMAPK33 could play a negative role in
salt tolerance through unfavourable ion homeostasis. Gene expression profiling of OsMAPK33 transgenic lines through
rice DNA chip analysis showed that OsMAPK33 altered expression of genes involved in ion transport. Further
characterization of downstream components will elucidate various biological functions of this novel rice MAPK.
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Lee Seong-Kon, Kim Beom-Gi, Kwon Taek-Ryoun, Jeong Mi-Jeong, Park Sand-Ryeol, Lee Jung-Won, Byun Myung-Ok, Kwon Hawk-Bin, Matthews Benjamin F,Hong Choo-Bong, Park Soo-Chul. Overexpression of the mitogen-activated protein kinase gene OsMAPK33 enhances sensitivity to salt stress in rice (Oryza sativa L.). Journal of Biosciences. 2011 Mar; 36(1): 139-151.