Molecular identification of a soybean protein kinase gene family by using PCR

Characterization of an AGAMOUS homologue from the conifer black spruce (Picea mariana) that produces floral homeotic conversions when expressed in Arabidopsis

Advances in elucidating the molecular processes controlling flower initiation and development have provided unique opportunities to investigate the developmental genetics of non-flowering plants. In addition to providing insights into the evolutionary aspects of seed plants, identification of genes regulating reproductive organ development in gymnosperms could help determine the level of homology with current models of flower induction and floral organ identity. Based upon this, we have searched for putative developmental regulators in conifers with amino acid sequence homology to MADS-box genes. PCR cloning using degenerate primers targeted to the MADS-box domain revealed the presence of over 27 MADS-box genes within black spruce (Picea mariana), including several with extensive homology to either AP1 or AGAMOUS, both known to regulate flower development in Arabidopsis. This indicates that like angiosperms, conifers contain a large and diverse MADS-box gene family that probably includes regulators of reproductive organ development. Confirmation of this was provided by the characterization of an AGAMOUS-like cDNA clone called SAG1, whose conservation of intron position and tissue-specific expression within reproductive organs indicate that it is a homologue of AGAMOUS. Functional homology with AGAMOUS was demonstrated by the ability of SAG1 to produce homeotic conversions of sepals to carpels and petals to stamens when ectopically expressed in transgenic Arabidopsis. This suggests that some of the genetic pathways controlling flower and cone development are homologous, and antedate the 300-million-year-old divergence of angiosperms and gymnosperms.

Differential accumulation of the transcripts of 22 novel protein kinase genes in Arabidopsis thaliana

22 novel members of the Arabidopsis thaliana protein kinase family (AKs) were identified by using degenerate oligonucleotide primers directed to highly conserved amino acid sequences of the protein kinase (PK) catalytic domain. Of these 22 genes, 16 turned out to carry intron sequences. Homologies of AK sequences were detected to S-locus receptor protein kinases (SRKs) from Brassica spp., to SRK-like PKs from maize and A. thaliana and to several other receptor PKs from A. thaliana. Sequence similarity was also detected to Ca(2+)-dependent PKs (CDPKs) from rape and soybean, to SNF1 and to CDC2 homologues. The genomic organization and the accumulation of the mRNAs from these 22 AK genes were investigated.

Molecular cloning of an Entamoeba histolytica gene encoding a putative mos family serine/threonine-kinase

Molecular cloning techniques were used to isolate an ameba gene encoding a putative 33-kDa serine/thyronine-kinase. The open reading frame of this gene, called Ehmfk1 for E. histolytica mos family kinase, shows a 24% positional identity with the human proto-oncogene mos, including 32 of 33 amino acids conserved in other serine/threonine-kinases.

Cloning and characterization of a novel member of protein kinase family from soybean

The cDNA coding for a novel protein kinase from soybean (Glycine max L.), named GmPK6, was sequenced. The primary sequence of GmPK6 consists of 462 amino acids with an N-terminal sequence similar to the central region of Xenopus U1 snRNP 70K protein, and a C-terminal kinase domain representing structural mosaicism with features diagnostic of both protein serine/threonine and tyrosine kinases in eukaryotic organisms. The GmPK6 gene is expressed as 2.5 kb transcript in a variety of tissues.

Biochemical evidence that phytochrome of the moss Ceratodon purpureus is a light-regulated protein kinase

The phytochrome gene of the moss Ceratodon purpureus (phyCer) codes for a novel phytochrome polypeptide with a predicted molecular mass of 145 kDa that has a COOH-terminal domain which is homologous to the catalytic domain of eukaryotic protein kinases. In this paper we report the first biochemical evidence that in fact, as predicted from the gene sequence, PhyCer represents an active, light-regulated protein kinase. In vitro phosphorylation experiments with protonemata extracts revealed the existence of a 140 kDa protein, phosphorylated in a red/far-red light dependent manner. The binding of a polyclonal antibody directed to the protein kinase catalytic domain of PhyCer enhanced the phosphorylation of a 140 kDa band when assayed in a renaturation-auto-phosphorylation experiment with nitrocellulose bound protein. These findings strongly implicate that the phyCer gene product has protein kinase activity and is capable of auto-phosphorylation. The results of the renaturation-phosphorylation experiments were essentially the same, no matter whether protein extracts from light grown or dark adapted moss protonemata were used. Thus, phyCer expression most likely is not light regulated.

Cloning and characterization of two cDNAs encoding casein kinase II catalytic subunits in Arabidopsis thaliana

Two cDNA clones, ATCKA1 and ATCKA2, encoding casein kinase II (CKII) catalytic subunits, were cloned from Arabidopsis thaliana and their nucleotide sequences were determined. Both cDNAs contain 999 bp open reading frames and are 94% identical on the amino acid sequence level. The deduced amino acid sequences of ATCKA1 and ATCKA2 are very similar to that of the human CKII catalytic alpha subunit (72% homology). Northern blot analysis indicates that the ATCKA1 and ATCKA2 mRNAs are present in all plant organs, but that ATCKA1 transcript levels are quite low compared to those of ATCKA2. Genomic Southern blot analysis suggests that there are at least three CKII genes in the A. thaliana genome. We expressed the ATCKA1 and ATCKA2 cDNAs in Escherichia coli using a pET vector derivative and analyzed the expressed protein in vitro. The expressed ATCKA1 protein phosphorylated casein using either ATP or GTP. This activity was inhibited by heparin, indicating that the expressed protein has activity similar to those reported for animal and yeast CKII.