DNA Sequence Analysis of a Complementary DNA for Cold-Regulated Arabidopsis Gene cor15 and Characterization of the COR 15 Polypeptide

Previous studies have indicated that changes in gene expression occur in Arabidopsis thaliana L. (Heyn) during cold acclimation and that certain of the cor (cold-regulated) genes encode polypeptides that share the unusual property of remaining soluble upon boiling in aqueous solution. Here, we identify a cDNA clone for a cold-regulated gene encoding one of the “boiling-stable” polypeptides, COR15. DNA sequence analysis indicated that the gene, designated cor15, encodes a 14.7-kilodalton hydrophilic polypeptide having an N-terminal amino acid sequence that closely resembles transit peptides that target proteins to the stromal compartment of chloroplasts. Immunological studies indicated that COR15 is processed in vivo and that the mature polypeptide, COR 15m, is present in the soluble fraction of chloroplasts. Possible functions of COR 15m are discussed.     

Two loci on wheat chromosome 5A regulate the differential cold-dependent expression of the cor14b gene in frost-tolerant and frost-sensitive genotypes

Although cold acclimation in cereals involves the expression of many cold-regulated genes, genetic studies have shown that only very few chromosomal regions carry loci that play an important role in frost tolerance. To investigate the genetic relationship between frost tolerance and the expression of cold-regulated genes, the expression and regulation of the wheat homolog of the barley cold-regulated gene cor14b was studied at various temperatures in frost-sensitive and frost-tolerant wheat genotypes. At 18/15 °C (day/night temperatures) frost-tolerant plants accumulated cor14b mRNAs and expressed COR14b proteins, whereas the sensitive plants did not. This result indicates that the threshold temperature for induction of the wheat cor14b homolog is higher in frost-resistant plants, and allowed us to use this polymorphism in a mapping approach. Studies made with chromosome substitution lines showed that the polymorphism for the threshold induction temperature of the wheat cor14b homolog is controlled by a locus(i) located on chromosome 5A of wheat, while the cor14b gene was mapped in Triticum monococcum on the long arm of chromosome 2A^m. The analysis of single chromosome recombinant lines derived from a cross between Chinese Spring/Triticum spelta 5A and Chinese Spring/Cheyenne 5A identified two loci with additive effects that are involved in the genetic control of cor14b mRNA accumulation. The first locus was tightly linked to the marker psr911, while the second one was located between the marker Xpsr2021 and Frost resistance 1 (Fr1). Received: 20 July 1999 / Accepted: 15 November 1999     

Function and molecular evolution of mammalian Sox15, a singleton in the SoxG group of transcription factors

In mammals, the group G of the Sry-related high-mobility-group (HMG) box genes (Sox) contains only one member, Sox15. Comparative genomic analysis of the Sox genes in the B1 and G groups indicates that an ancestral gene may have originated as an intron-containing gene belonging to group B1 and evolved into zebrafish Sox19a/b, Xenopus SoxD, and mammalian Sox15. Although these genes have different names, they are orthologous. The zebrafish and Xenopus orthologues are highly expressed in the central nervous system, whereas mouse Sox15 only shows strong expression in the placenta, an organ characteristic of all mammals except monotremes. Interestingly, Sox15 appears to be a pseudogene in the marsupial opossum. Sox15-deficient mice exhibit delayed skeletal muscle regeneration, indicating that Sox15 plays a crucial role in this process. On the other hand, Xenopus SoxD induces anterior neural development. Thus, there appears to be little functional overlap between Sox15 and its orthologues, Sox19a/b and SoxD. In this review, I discuss the roles of Sox15, its functional redundancy with SoxB1 group members, and its molecular evolution.     

Enantiomeric lignans with anti-β-amyloid aggregation activity from the twigs and leaves of Pithecellobium clypearia Benth

To develop potential agents for slowing the progression of Alzheimer′s disease, two pairs of new enantiomeric lignans, including a couple of rarely 8′,9′-dinor-3′,7-epoxy-8,4′-oxyneolignanes named (7S, 8S)- and (7R, 8R)-pithecellobiumin A (1a/1b) and a pair of 2′,9′-epoxy-arylnaphthalenes named (7R, 8R, 8′R)- and (7S, 8S, 8′S)-pithecellobiumin B (2a/2b) were separated by chiral high performance liquid chromatography (HPLC). Their planar structures were elucidated by spectroscopic data analyses. The absolute configurations were determined by comparing of experimental and calculated electronic circular dichroism (ECD). The inhibitory activity on Aβ aggregation of all optical pure compounds was tested by ThT assay. Interestingly, enantiomeric inhibitors 1a (62.1%) and 1b (81.6%) exhibited different degrees of anti-Aβ aggregation activity. However, 2a (65.4%) and 2b (68.4%) showed similar inhibition rate. The different inhibition profiles were explained by molecular dynamics and docking simulation studies.     

Structure, organization and expression of the metallothionein gene family inArabidopsis

Metallothioneins (MTs) are cysteine-rich proteins required for heavy metal tolerance in animals and fungi. Recent results indicate that plants also possess functional metallothionein genes. Here we report the cloning and characterization of five metallothionein genes fromArabidopsis thaliana. The position of the single intron in each gene is conserved. The proteins encoded by these genes can be divided into two groups (MT1 and MT2) based on the presence or absence of a central domain separating two cysteine-rich domains. Four of the MT genes (MT1a,MT1c,MT2a andMT2b) are transcribed inArabidopsis. Several lines of evidence suggest that the fifth gene,MT1b, is inactive. There is differential regulation of the MT gene family. MT1 mRNA is expressed highly in roots, moderately in leaves and is barely detected in inflorescences and siliques. MT2a and MT2b mRNAs are more abundant in leaves, inflorescences and in roots from mature plants, but are also detected in roots of young plants, and in siliques. MT2a mRNA is strongly induced in seedlings by CUSO₄, whereas MT2b mRNA is relatively abundant in this tissue and levels increase only slightly upon exposure to copper.MT1a andMT1c are located within 2 kb of each other and have been mapped to chromosome 1.MT1b andMT2b map to separate loci on chromosome V, andMT2a is located on chromosome III. The locations of these MT genes are different from that ofCAD1, a gene involved in cadmium tolerance inArabidopsis.     

Structure,organization and expression of the metallothionein gene family inArabidopsis

Metallothioneins (MTs) are cysteine-rich proteins required for heavy metal tolerance in animals and fungi. Recent results indicate that plants also possess functional metallothionein genes. Here we report the cloning and characterization of five metallothionein genes fromArabidopsis thaliana. The position of the single intron in each gene is conserved. The proteins encoded by these genes can be divided into two groups (MT1 and MT2) based on the presence or absence of a central domain separating two cysteine-rich domains. Four of the MT genes (MT1a,MT1c,MT2a andMT2b) are transcribed inArabidopsis. Several lines of evidence suggest that the fifth gene,MT1b, is inactive. There is differential regulation of the MT gene family. MT1 mRNA is expressed highly in roots, moderately in leaves and is barely detected in inflorescences and siliques. MT2a and MT2b mRNAs are more abundant in leaves, inflorescences and in roots from mature plants, but are also detected in roots of young plants, and in siliques. MT2a mRNA is strongly induced in seedlings by CUSO₄, whereas MT2b mRNA is relatively abundant in this tissue and levels increase only slightly upon exposure to copper.MT1a andMT1c are located within 2 kb of each other and have been mapped to chromosome 1.MT1b andMT2b map to separate loci on chromosome V, andMT2a is located on chromosome III. The locations of these MT genes are different from that ofCAD1, a gene involved in cadmium tolerance inArabidopsis.     

Common Precursor for Rauscher Leukemia Virus gp69/71, p15(E), and p12(E)

Rauscher murine leukemia virus glycoprotein gp69/71 and non-glycosylated p15(E) are synthesized by way of a 90,000-dalton precursor glycoprotein, termed Pr2a+b. Peptide mapping experiments showed that Pr2a+b contains all the tyrosine-containing tryptic peptides of gp69/71. Two additional tyrosine-containing tryptic peptides in Pr2a+b that are not detected in gp69/71 are found in p15(E). Thus, gp69/71 and p15(E) peptide sequences account for all the tyrosine tryptic peptides of Pr2a+b. The gene order of the two proteins was determined by pulse-labeling infected cells in the presence and absence of pactamycin at concentrations of the inhibitor that prevent initiation of translation, but not elongation. The gene order was found to be: ₂HN-gp69/71-p15(E)-COOH. A newly identified major viral protein, termed p12(E), migrates in sodium dodecyl sulfate-polyacrylamide gels in the “p12” region. It is related to p15(E) as determined by tryptic mapping experiments. p15(E) and p12(E) are not phosphorylated, and both can be separated from phosphoprotein p12 by guanidine hydrochloride-agarose chromatography. p12(E) and p15(E) elute in the void volume fraction, whereas phosphoprotein p12 elutes between p15 and p10. The two p12 proteins can also be separated from each other by two-dimensional gel electrophoresis involving isoelectric focusing in the first dimension and sodium dodecyl sulfate-gel electrophoresis in the second dimension.