Abstract
Protein phosphorylation and dephosphorylation are implicated in the development of freezing tolerance during cold acclimation in plants. We previously showed that freezing tolarance of moss Physcomitrella patens protonema cells increased by treatment with ABA, cold. We isolated the PARK gene encoding protein Ser/Thr kinase induced by ABA and cold. The PARK kinase domain was similar to S-domain receptor like protein kinase, but it did not possess the extracellular domain.
The GST-PARK fusion protein phosphorylated histon IIIS and myelin basic protein and that the kinase itself underwent rapid autophosphorylation. When the PARK-GFP fusion gene was introduced into plant cells, the fluorescence signal was observed in the plasma membrane. Gene knock-out plants of PARK had reduced survival rates after freezing as compared to the wild type plants. These results indicate that PARK might regulate signal transduction processes of ABA- or cold-induced freezing tolerance.
