Tyrosine phosphatase signalling in a lower plant: cell-cycle and oxidative stress-regulated expression of the Chlamydomonas eugametos VH-PTP13 gene |
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Authors: | Michel A. Haring Marco Siderius Claudia Jonak Heribert Hirt Kevin M. Walton Alan Musgrave |
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Affiliation: | Biocentrum Amsterdam, Institute for Molecular Cell Biology, University of Amsterdam, Kruislaan 318, 1098 SM Amsterdam, The Netherlands;Institut für Mikrobiologie und Genetik, Universität Wien, Vienna Biocenter, Dr. Bohrgasse 9, Wien 1030, Austria;The University of Michigan Medical School, Dept of Biological Chemistry, Ann Arbor, MI 48109-0606 USA |
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Abstract: | The first evidence for tyrosine phosphatase signalling pathways in plants is presented by characterizing a putative protein tyrosine phosphatase gene from the unicellular green alga Chlamydomonas eugametos . This cDNA, referred to as VH-PTP13 , contains an open reading frame specifying a protein with a molecular weight of 30.3 kDa, that has significant homology with a distinct group of dual-specificity phosphatases. The highest homology is found with CL-100 , a human stress-response gene that regulates MAPkinase activity. The purified VH-PTP13 protein expressed in E. coli had phosphatase activity and inactivated MAPkinases from alfalfa and tobacco. Non-dividing C. eugametos gametes did not express the VH-PTP13 gene whereas synchronously dividing vegetative cells only expressed VH-PTP13 in the early G1-phase of the cycle, implying a function there. When vegetative cells were subjected to oxidative stress, expression of the VH-PTP13 gene was strongly induced, analogous to the human CL-100 gene. Its potential role in plant signalling pathways is discussed. |
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