Alignment and phylogenetic relationships of ACPK1 and its related members of the CDPK family. We added the following prefixes to the names of some cited CDPKs in this paper for distinguishing them easily if their original names do not contain the prefixes: At for Arabidopsis, Gm and GmS (S indicates seed) for soybean, Os for rice, St for potato, Vf for broad bean, and Zm for maize. A, Alignment of deduced amino acid sequences of ACPK1 and one of its closest homologs, soybean seed CDPKa (GmS-CDPKa), shows the presence of conserved features in Ser/Thr (S/T) protein kinase domain, junction domain, and CaM-like domain and also variable features in N-terminal domain and C-terminal tail. Numbers on the right column indicate numbers of amino acid residues in the predicted sequences. Gaps, indicated by dashes (–), were introduced to maximize alignment. Identical amino acid residues are indicated by white letters on a black background. The boundaries of the N-terminal variable domain, S/T kinase domain, junction domain, CaM-like domain, and C-terminal tail are indicated by arrows. Four EF-hand motifs (EFh) and five potential myristoylation sites (ML1-5) are also shown. The matched sequences of seven peptides obtained in the first sequencing of the purified 58-kD ABA-stimulated CDPK (natural ACPK1 protein, see Fig. 7) by TMS are marked by Peptide 1 to Peptide 7 underneath the GmS-CDPKa sequence, respectively. The degenerate oligonucleotides corresponding to the conserved sequences of the peptide 1 in kinase domain (forward primer) and peptide 5 in junction domain (reverse primer) were used for cloning the putative ACPK1. The underlined sequences of ACPK1 are the matched sequences obtained in the second sequencing of the natural ACPK1 protein by TMS after the cDNA coding for the putative ACPK1 was isolated. B, Tree depicting phylogenetic relationships based on alignment of deduced amino acid sequences among top 11 of CDPKs having higher identity with ACPK1 and the other three ABA-responsive CDPKs, NtCDPK1 (Yoon et al., 1999), and AtCPK10 and AtCPK 30 (Sheen, 1996). Percentages of amino acid sequence identity are also indicated. The corresponding accession numbers or locus tag numbers for the genes encoding these CDPKs are given in the section “Accession Numbers” in “Materials and Methods.”