A Triticum tauschii protein kinase related to wheat PKABA1 is associated with ABA signaling and is distributed between the nucleus and cytosol

A new member of the cereal PKABA1 subfamily of protein kinases, TtPK1, was isolated from Triticum tauschii, a diploid progenitor of hexaploid wheat, Triticum aestivum. The full-length TtPK1 cDNA was cloned from a library derived from vegetative tissues from 26 d old light grown T. tauschii seedlings. TtPK1 cDNA hybridizes to transcripts that are upregulated in dehydrated leaves and are abundant in coleoptile tissue of 7 d old T. aestivum seedlings. TtPK1 mRNA has nucleotide identities of 82 and 79% to PKABA1 and TaPK3, respectively, and deduced amino acid sequence identities of 84 and 83% to PKABA1 and TaPK3, respectively. TtPK1 is similar to members of the SnRK2 subfamily of protein kinases in that it contains a unique acidic domain at the carboxyl terminus, and all twelve of the conserved subdomains found in serine/threonine protein kinases. Functional analyses of TtPK1 transiently over-expressed by bombarding barley half-grains showed that TtPK1 could suppress gibberellic acid inducible alpha-amylase gene expression, a suppressive activity similar to that of both PKABA1 and ABA. When transiently expressed in barley aleurone protoplasts, TtPK1-GFP accumulates in the nucleus and cytosol while a mutant TtPK1-GFP was localized only to the cytoplasm and vacuoles.