Two novel mitogen-activated protein signaling components, OsMEK1 and OsMAP1, are involved in a moderate low-temperature signaling pathway in rice.
Rice (Oryza sativa) anther development is easily damaged by moderately low temperatures above 12 degrees C. Subtractive screening of cDNA that accumulated in 12 degrees C-treated anthers identified a cDNA clone, OsMEK1, encoding a protein with features characteristic of a mitogen-activated protein (MAP) kinase kinase. The putative OsMEK1 protein shows 92% identity to the maize (Zea mays) MEK homolog, ZmMEK1. OsMEK1 transcript levels were induced in rice anthers by 12 degrees C treatment for 48 h. Similar OsMEK1 induction was observed in shoots and roots of seedlings that were treated at 12 degrees C for up to 24 h. It is interesting that no induction of OsMEK1 transcripts was observed in 4 degrees C-treated seedlings. In contrast, rice lip19, encoding a bZIP protein possibly involved in low temperature signal transduction, was not induced by 12 degrees C treatment but was induced by 4 degrees C treatment. Among the three MAP kinase homologs cloned, only OsMAP1 displayed similar 12 degrees C-specific induction pattern as OsMEK1. A yeast two-hybrid system revealed that OsMEK1 interacts with OsMAP1, but not with OsMAP2 and OsMAP3, suggesting that OsMEK1 and OsMAP1 probably function in the same signaling pathway. An in-gel assay of protein kinase activity revealed that a protein kinase (approximately 43 kD), which preferentially uses myelin basic protein as a substrate, was activated by 12 degrees C treatment but not by 4 degrees C treatment. Taken together, these results lead us to conclude that at least two signaling pathways for low temperature stress exist in rice, and that a MAP kinase pathway with OsMEK1 and OsMAP1 components is possibly involved in the signaling for the higher range low-temperature stress.
Winter Stress Laboratory, National Agricultural Research Center for Hokkaido Region, Hitsujigaoka 1, Toyohira-ku, Sapporo 062-8555, Japan.
Jiang-Qi
JQ
Wen
Kiyoharu
K
Oono
Ryozo
R
Imai
D000040:Abscisic Acid / Q000494:pharmacology; D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D003080:Cold Temperature; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology; D020798:Two-Hybrid System Techniques; D014867:Water / Q000494:pharmacology
D018076:DNA, Complementary; D010940:Plant Proteins; D014867:Water; D012965:Sodium Chloride; D000040:Abscisic Acid; D020929:Mitogen-Activated Protein Kinase Kinases