Molecular cloning and characterization of a cDNA encoding a kinase in Cucumis sativus and its expression by abiotic stress treatments.

As a part of an integrated study of stress-related gene expression, a cDNA clone coding for a protein kinase in the root of Cucumis sativus was isolated and characterized with respect to its sequence and the expression patterns upon various abiotic stress treatments. The predicted polypeptide of 352 amino acid residues contains characteristic features of both the serine/threonine and tyrosine kinase families. In vitro kinase assay confirmed that the isolated protein kinase has autophosphorylation activity. Southern blot analysis showed that the kinase gene is a single-copy gene. Northern blot analysis showed that the kinase gene was more abundantly expressed in the roots and shoots than in the leaves. A quantitative real-time reverse-transcription-polymerase chain reaction analysis revealed that, among the abiotic stresses tested, drought treatment markedly decreased the transcript level of the kinase, whereas the expression of the kinase gene significantly increased by cold treatment. High salinity did not influence its expression. The present report identifies a dual specificity protein kinase in cucumber that shows different responses to abiotic stress treatments.