Abstract
Four species of protein kinase were identified in senescent maize leaves using a gel assay for kinase activity with myelin basic protein (MBP) as the substrate. Most of these kinases were also found in healthy green leaves that had been exposed to low-temperature stress (5° C) and then returned to 25° C. A 41-kDa protein was activated in senescent leaves, whereas a 45-kDa protein was activated 3 h after up-shift from 5° C to 25° C as well as in senescent leaves. A 39-kDa protein was activated by cold stress. The other two proteins, of 35 kDa and 52 kDa, constitutively phosphorylated MBP during senescence and temperature up-shift. Judging from their molecular masses, cation requirements and substrate specificities, it seemed likely that the 39-kDa, 41-kDa and 45-kDa proteins represented mitogen-activated protein kinases (MAPKs). Subsequently two MAPK cDNAs were isolated from a cDNA library constructed using mRNAs from senescent leaves. Northern analysis showed that the transcript corresponding to one of the cDNAs, designated ZmMPK5, accumulated in healthy leaves 3 h after the up-shift to 25° C as well as in senescent leaves, suggesting that the 45-kDa protein kinase is encoded by ZmMPK5. Western analysis using an antiserum against the C-terminal region of ZmMPK5 showed that the level of the ZmMPK5 protein increased in senescent leaves. These results indicate that a 45-kDa MAPK is involved in the process of senescence and in recovery from low-temperature stress in maize plants.
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Received: 31 May 1999 / Accepted: 21 July 1999
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Berberich, T., Sano, H. & Kusano, T. Involvement of a MAP kinase, ZmMPK5, in senescence and recovery from low-temperature stress in maize. Mol Gen Genet 262, 534–542 (1999). https://doi.org/10.1007/s004380051115
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DOI: https://doi.org/10.1007/s004380051115