Initial stages of low-temperature induction of cabbage cold shock protein gene csp5.

Some stages of low-temperature signal transduction causing appropriate cold stress response in plants are considered. The effects of Ca2+ chelators, Ca2+ channel blockers, and protein kinase inhibitors on protoplasts and plants of cabbage suggest that the initial stages of cold signal transduction are the change in membrane fluidity followed by the activation of calcium channels and elevation of Ca2+ influx into the cytoplasm. Increased concentration of Ca2+ in cytoplasm activates calcium-dependent protein kinase most likely participating in induction of transcription factors necessary for the expression of cold-regulated genes, in particular csp5. The protein kinase inhibitors staurosporine and wortmannin insignificantly repress the expression of csp5.

The plant dehydrins: structure and putative functions.

This review deals with recent data on the structure and biochemical properties of dehydrins, proteins that are normally synthesized in maturating seeds during their desiccation, and also in vegetative tissues of plants treated with abscisic acid or exposed to environmental stress factors that result in cellular dehydration. The dehydrins are considered as stress proteins involved in formation of plant protective reactions against dehydration. The generally accepted classification of dehydrins is based on their structural features, such as the presence of conserved sequences, designated as Y-, S-, and K-segments. The K-segment representing a highly conserved 15 amino acid motif (EKKGIMDKIKEKLPG) forming amphiphilic alpha-helix has been found in all dehydrins. The pathways of regulation of dehydrin gene expression, putative functions of dehydrins, and molecular mechanisms of their actions are discussed.

[Phylogeny of Triticum L. and Aegilops L. genuses inferred from a comparative analysis of nucleotide sequences in promoter rDNA regions of individual species]. / Filogeneticheskie vzaimootnosheniia rodov Triticum L. i Aegilops L. i nukleotidnye posledovatel'nosti promotornykh obtastei rDNK ikh otdel'enykh predstavitelei.

The process of accumulation of knowledge on wheat and related wild species during the 20th century is briefly reviewed with special reference to the evidence of the recent years on evolution of polyploid wheats and the role of diploid species. The latter serve as potential donors of the genomes, detection of which is particularly important because of the continuing speciation in the tribe Triticeae and artificial development of synthetic forms. The arguments in favor of the donor role for various diploid wheat species and aegilopses from the section Sitopsis are compared. It is stated that in the formation of the both lines of polyploid wheats turgidum-aestivum and timopheevi, diploid Aegilops speltoides acted as a maternal form. In addition to plasmatic genomes, this aegilops species introduced into them also the B and G nuclear subgenomes. A comparison of nucleotide sequences in the variable part of the promoter of evolutionary conserved rRNA genes in polyploid wheats with their counterparts in diploid wheats and aegilopses confirmed the accepted wheat phylogenies.

[The frequencies of the low-molecular-weight alanine-rich cold shock proteins genes and variation of their primary structure in plants of temperate climate]. / Rasprostranennost' genov nizkomolekuliarnykh alaninbogatykh belkov "kholodovogo shoka" v rasteniiakh umerennogo klimata i variabel'nost' ikh pervichnoi struktury.

Polymerase chain reaction (PCR) was used to study the frequencies of the gene of a low-molecular-weight alanine-rich cold shock protein in plants of temperate climate. This gene was demonstrated to be specific for the family Cruciferae. Its variability in this family was studied.

[Intragenomic polymorphism of the primary structure of 5S rRNA gene variants of the loach (Misgurnus fossilis L.). Determination of the transcriptional activity]. / Vnutrigenomnyi polimorfizm pervichnoi struktury variantov genov 5S rRNK v'iuna (Misgurnus fossilis L.). Opredelenie transkriptsionnoi aktivnosti.

The primary structure of 12 cloned repeats of loach oocyte 5S rRNA genes was determined. The heterogeneity of nucleotide sequences was revealed in the coding regions and spacer of the genes. The results of the study on in vivo transcriptional activity of the cloned 5S rRNA gene variants are consistent with the localisation of site specific base substitutions in the coding part affecting the transcription. We have compared the nucleotide sequences of loach 5S rRNA gene variants and of Xenopus laevis, X. borealis and Bombyx mori 5S genes which can be actively transcribed in X. laevis oocyte nuclei. As a result we could propose a consensus nucleotide sequence in the internal control region (from 45-th up to 100-th nucleotide) of the eukaryotic 5S rRNA gene. This sequence comprises a RNA-polymerase III promotor and stretches interacting with transcriptional factors. We have considered the base substitutions in the nucleotide sequences of 5S gene variants exerted on the experimental model of loach 5S rRNA secondary structure. All base substitutions in actively transcribed genes do not influence the general double-stranded structures of the transcripts. However in 5S RNA transcripts from genes with low transcriptional activity base substitutions affecting the box c RNA-polymerase III promoter destroy hairpin II interacting with ribosomal proteins. We have concluded that two factors can restrict the divergency of 5S rRNA genes: (1) conservation of the nucleotide sequence in the gene internal control region, and (2) conservation of the general double stranded structures in 5S rRNA transcripts.

[Nucleotide sequences of 5S rRNA genes of polyploid species of wheat and Aegilops species]. / Nukleotidnye posledovatel'nosti genov 5S rRNK poliploidnykh vidov pshenitsy i ikh dikikh sorodichei.

Primary structures of 5S rRNA genes and of non-transcribed spacers between them were determined in families of 5S DNA repeats 420 and 500 b.p. long in 8 wheat and Aegilops species. The high conservatism of sequences coding for 5S rRNA, 3'- and 5'-ends of non-transcribed spacers was shown not to depend on the evolutional position, ploidy level and genomic composition of species. The activity of transcription of 5S rRNA cloned genes was determined in vitro. The functional heterogeneity was revealed in each family of repeats due to the existence of exchanges of separate nucleotides within the internal transcription control region. A greater deficiency of CpG dinucleotide was revealed in 5S rRNA genes than in non-transcribed spacers.

[Primary structure of the 5S rRNA gene and its flanking sequences in diploid Aegilops tauschii Coss]. / Pervichnaia struktura gena 5S rRNK i flankiruiushchikh ego posledovatel'nostei u diploidnogo egilopsa Aegilops tauschii Coss.

In genome of diploid aegilops A. tauschii (k773) two types of sequences 420 and 510 b. p. long which hybridize with 5S[32P]rRNA were discovered. Using the plasmid pBR327 the recombinant plasmids pAt5S79 and pAt5S91 containing 5S DNA repeats of Ae. tauschii were constructed. The primary structure of 5S rRNA gene and that of intergene spacer cloned in pAt5S79 was determined. In gene region of Ae. tauschii coding for 5S rRNA, as compared with T. aestivum, there were found 3 base substitutions in positions 24, 36 and 37. The homology of spacer sequences is 79.1%. In 5S rRNA gene of Ae. tauschii GC-content is 53.3%, but in a spacer--48.1%. The terminator of transcription in Ae. tauschii includes 15 AT-base pairs with predomination of T-bases in uncoding chain.