|Matthews, Benjamin - Ben|
Submitted to: Journal of Bioscience and Bioengineering
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/6/2010
Publication Date: 3/20/2011
Citation: Lee, S., Kim, B., Kwon, T., Jeong, M., Park, S., Lee, J., Byun, M., Kwon, H., Matthews, B.F., Hong, C., Park, S. 2011. Overexpression of the MAP kinase gene OsMAPK33 enhances sensitivity to salt stress in rice (Oryza sativa L.). Journal of Bioscience and Bioengineering. 36:139-151. Interpretive Summary: Drought and salt stress influence crop health and limiting crop yield. Drought stress in soybean is of particular importance at planting and during reproductive stages, while salt stress is important to soil infertility in arid regions. A plant responds to environmental stresses and pathogen attack by sensing the stress and signaling to response regions of the plant to turn on the appropriate genes and synthesize the appropriate proteins in an effort to combat the stress. We cloned a gene from rice encoding a signaling protein named mitogen-activated protein kinase (MAPK)and studied the role of the gene during environmental stress and pathogen attack. Our results demonstrate that this gene does not appear to play a major role in the plant’s ability to combat drought, but the gene may play a role in promoting the uptake of salt into the plant. This information provides on an important gene that may be useful to develop soybean with broader resistance to salt stress.
Technical Abstract: Mitogen-activated protein kinases (MAPK) signaling cascades are activated by extracellular stimuli such as environmental stresses and pathogens in higher eukaryotic plants. To know more about MAPK signaling in plants, a MAPK cDNA clone, OsMAPK33 was isolated from rice. The gene is mainly induced by drought stress. OsMAPK33 (Os02g0148100) showed approximately 47-93% identity at the amino acid level with other plant MAPKs in phylogenetic analysis. It was found to exhibit organ-specific expression with relatively higher expression in leaves as compared to roots or stems, and to exist as a single copy in the rice genome. To investigate the biological functions of OsMAPK33 in rice MAPK signaling, transgenic rice plants were made that either overexpressed or suppressed OsMAPK33. Under dehydration conditions, the suppressed lines showed lower osmotic potential compared to 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 cell than that of the wild type plants and OsMAPK33 suppressed lines. These results suggest that OsMAPK33 could play a negative role in salt tolerance through unfavorable 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 further.