[Genetic base of Arabidopsis thaliana (L.) Heynh: fitness of plants for extreme conditions in northern margins of species range].

Flowering time and vernalization requirement were studied in eight natural Karelian populations (KPs) of Arabidopsis thaliana. These KPs consisted of late-flowering plants with elevated expression of flowering repressor FLC and a reduced expression level of flowering activator SOC1 compared to the early-flowering ecotypes Dijon-M and Cvi-0. Despite variations in flowering time and the vernalization requirement among the KPs, two-week-old seedlings showed no changes in either the nucleotide sequence of the FRI gene or the relative expression levels of FRI and its target gene FLC that would be responsible for this variation. An analysis of abscisic acid (ABA) biosynthesis and catabolism genes (NCED3 and CYP707A2) did not show significant differences between late-flowering KPs and the early-flowering ecotypes Dijon-M and Cvi-0. Cold treatment (4 degrees C for 24 h) induced the expression of not only NCED3, but also RD29B, a gene involved in the ABA-dependent cold-response pathway. The relative levels of cold activation of these genes were nearly equal in all genotypes under study. Thus, the ABA-dependent cold response pathway does not depend on FLC expression. The lack of significant differences between northern populations, as well as the ecotypes Dijon-M (Europe) and Cvi-0 (Cape Verde Islands), indicates that this pathway is not crucial for fitness to the northern environment.

[Study of the effect of the gene ERECTA2 on the development of Arabidopsis thaliana shoot].

The role of the gene ER2 in plant development has been studied by the analysis of the erecta2 (er2) mutant of Arabidopsis thaliana (L.) Heynh. It was shown that the mutation er2 provides pleiotropic effect on the development of all aboveground organs. It induces shortening and thickening of the stem, leaves and all flower organs, though it does not change the sensitivity to gibberellin. Changes in the morphology of the shoot organs are due to the changes in cell polarity. The cells get wider and shorter compared to the wild type. It was found that the gene ER2 is located in the lower arm of the chromosome 1. It complementarily interacts with the gene ER that plays an important role in the control of intercellular interactions.

[Different action of the APETALA1 gene on the development of reproductive organs in flowers of the abruptus mutant of Arabidopsis thaliana (L.) Heynh].

The APETALA1 (AP1) gene of A. thaliana codes type II MADS protein with domains MADS, I, K, and C. The role of K- and C-domains in the functioning of AP1 protein is poorly investigated. The analysis of phenotypic manifestation of mutations disrupting the activity of various domains of the protein product allows us to obtain information on the function of domains and, thereby, on the structural-functional organization of the gene. We investigated the action of mutant alleles of the AP1 gene whose protein products are probably lacking the functionally active domains K (ap1-20), K- and C-domains (ap1-1 and ap1-6), and C-domain (ap 1-3) on the flower morphology in abr mutant (the ABRUPTUS/PINOID gene allele). It was detected that, unlike the ap 1-20 allele, the presence of ap 1-3, ap1-6, and ap 1-1 alleles results in reduction of a number of the generative organs in the flowers of the double mutants abr ap1-3, abr ap1-6, and abr ap1-1. It was suggested that C-domain of the AP1 protein prevents the alteration of determination of the type of reproductive organs at ectopic expression of the AP1 gene in the inner whorls of a flower in the abr mutant.

[Interspecies polymorphism of peroxidase genes, localized on chromosome 5 of Arabidopsis thaliana].

Comparative analysis of nucleotide sequences in five peroxidase genes AtPrx52-AtPrx56 located in the left arm of chromosome 5 was performed by using six Arabidopsis thaliana ecotypes and lines (Columbia, Dijon-M, Blanes-M, Enkheim-M, Ler, K-156). Significal differences (up to 20 times) in the levels of nucleotide variation between these genes were detected: tandem duplicated genes AtPrx53 and AtPrx54 have the highest and the AtPrx56 gene has the lowest level of nucleotide diversity. The genes AtPrx53 and AtPrx54 were characterized by allelic dimorphism; the nonrandom association between nucleotide polymorphic sites within the AtPrx54 was shown. The connection between gaplotype of these genes and the mobility of anionic peroxidase izoforms was detected. Since two gaplotypes of AtPrx53 were coding proteins, which differed by two significant amino acid substitutions, we supposed that differences in mobility of anionic peroxidase izoforms caused by the diallelic polymorphism in amino acid sequence of AtPrx53 protein.

[Carboanhydrase activity in halophilic anaerobes from soda lakes].

The activity and cellular localization of carboanhydrase (CA) in two alkaliphilic anaerobes growing in soda lakes at pH 9-10 was studied. CA activity in the cell extracts of the acetogenic bacterium Natroniella acetigena was comparable to that of the neutrophilic acetogens. Hydrogenotrophically grown cells of Desulfonatronum lacustre exhibited higher CA activity compared to the cells grown on media with formate. High CA activity in the cytoplasmic fraction and the absence of high activity in the extracellular fraction were demonstrated. We propose that the cytoplasmic CA in alkaliphilic sulfate-reducers participates in conversion of bicarbonate to CO2, which is reduced in the cell to acetate via the acetyl-CoA pathway.

[Carbonic anhydrase of the alkaliphilic cyanobacterium Microcoleus chthonoplastes]. / Karboangidraza alkalofil'noi tsianobakterii Microcoleus chthonoplastes.

The activity of carbonic anhydrase (CA) was studied in different cell fractions of the alkaliphilic cyanobacterium Microcoleus chthonoplastes. The activity of this enzyme was found in the soluble and membrane protein fractions, as well as in intact cells and in a thick glycocalyx layer enclosing the cyanobacterium cells. The localization of CA in glycocalyx of M. chthonoplastes was shown by the western blot analysis and by immunoelectron microscopy studies with antibodies to the thylakoid CA from Chlamydomonas reinhardtii (Cah3). At least one of the CA forms occurring in M. chthonoplastes CA was shown to be an alpha-type enzyme. A possible mechanism of the involvement of the glycocalyx CA in calcification of cyanobacteria is discussed.

[Change in potassium ion homeostasis of the crystalline lens in mice with hereditary cataracts (the CatFr line)]. / Izmenenie ionnogo gomeostaza kaliia v khrustalke u myshei s nadsledstvennoi kataraktoi (liniia CatFr).

Fraeser mouse lens morphology and potassium homeostasis were studied. It was shown that just at the age of one month mouse lens exposed "bull" cells which could be observed in patients with senile cataract as well. Nucleated fusiform extended cells were found 4 months later in the central part of the lens which was not typical for this part of the whole normal lens. Studied homogenates of 34 mice with hereditary cataract demonstrated statistically significant increase (1.5-fold about) in K+-content estimated for the whole lens weight as compared to the control group (38 lens). The difference in potassium content in aqueous humor between affected and control animals was statistically indistinguishable. The role of potassium ions in Fraeser cataract pathogenesis is discussed.