Molecular characterization of a protein kinase gene in Chinese cabbage (Brassica campestris subsp. napus var. pekinensis)

Abstract

Random sequencing of expressed sequence tags in roots of Chinese cabbage led to isolation of a partial cDNA clone, BR77, which encoded a putative protein kinase. Using the BR77 cDNA as a probe, we isolated a full‐length cDNA encoding the Brassica campestris protein kinase 1 (Bcpk1). The Bcpki cDNA contained one open reading frame encoding a polypeptide of 439 amino acids. The putative polypeptide consisted of a short N‐terminal region and a protein kinase catalytic domain. The catalytic domain of Bcpk1 showed a high homology to cAMP‐ and calcium‐phospholipid‐dependent subfamilies of serine/threonine protein kinases. Eleven major catalytic domains in protein kinases were well conserved in Bcpk1. However, Bcpk1 contained a unique nonhomologous intervening sequence between subdomains VII and VIII, which was not found in protein kinases of animals and lower eukaryotes. Genomic DNA gel blot analysis showed that Bcpk1 genes might be present as three copies in the Chinese cabbage genome. These imply that Bcpk1 belongs to a plant‐specific serine/threonine protein kinase subfamily.

Key words:

• Brassica campestris subsp. napus var. pekinensis
• Root
• Protein kinase
• Serine/threonine protein kinase

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