Department of Agricultural Biotechnology, National Academy of Agricultural Science, Rural Development Administration, Suwon 441-857, Republic of Korea.
J Biosci. 2011 Mar;36(1):139-51. doi: 10.1007/s12038-011-9002-8.
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.
丝裂原活化蛋白激酶（MAPK）信号级联反应被高等真核植物的细胞外刺激如环境压力和病原体激活。为了更多地了解植物中的 MAPK 信号转导，从水稻中分离出一个 MAPK cDNA 克隆 OsMAPK33。该基因主要受干旱胁迫诱导。在系统发育分析中，OsMAPK33（Os02g0148100）在氨基酸水平上与其他植物 MAPKs 的同源性约为 47-93%。它表现出器官特异性表达，与根或茎相比，叶片中的表达相对较高，并且在水稻基因组中存在一个拷贝。为了研究 OsMAPK33 在水稻 MAPK 信号转导中的生物学功能，构建了过表达或抑制 OsMAPK33 的转基因水稻植株。在脱水条件下，抑制系的渗透势比野生型植物低，表明 OsMAPK33 在渗透稳态中起作用。然而，与野生型植物相比，抑制系在耐旱性方面没有表现出任何显著差异。随着盐度的增加，OsMAPK33 抑制系与野生型植物之间的耐盐性仍无差异。然而，过表达系表现出生物量积累减少和细胞内钠离子摄取增加，导致细胞内 K+/Na+ 比值低于野生型植物和 OsMAPK33 抑制系。这些结果表明，OsMAPK33 可能通过不利的离子稳态在耐盐性中发挥负作用。通过水稻 DNA 芯片分析对 OsMAPK33 转基因系的基因表达谱进行分析表明，OsMAPK33 改变了离子转运相关基因的表达。对下游成分的进一步表征将阐明这种新型水稻 MAPK 的各种生物学功能。
