Evolutionary Divergence of Arabidopsis thaliana Classical Peroxidases.

Polymorphisms of 62 peroxidase genes derived from Arabidopsis thaliana were investigated to evaluate evolutionary dynamics and divergence of peroxidase proteins. By comparing divergence of duplicated genes AtPrx53-AtPrx54 and AtPrx36-AtPrx72 and their products, nucleotide and amino acid substitutions were identified that were apparently targets of positive selection. These substitutions were detected among paralogs of 461 ecotypes from Arabidopsis thaliana. Some of these substitutions are conservative and matched paralogous peroxidases in other Brassicaceae species. These results suggest that after duplication, peroxidase genes evolved under the pressure of positive selection, and amino acid substitutions identified during our study provided divergence of properties and physiological functions in peroxidases. Our predictions regarding functional significance for amino acid residues identified in variable sites of peroxidases may allow further experimental assessment of evolution of peroxidases after gene duplication.

[Studying the role of FASCIATA5 gene in the regulation of flower development in Arabidopsis thaliana].

Identification of new genes involved in the control of flower initiation and development, is an important problem of the plant developmental genetics. Central approach to solve it is the study of mutants with changes in these characters. The effect of pleiotropic mutation fasciata5 on the transition to the reproductive stage and flower development was studied. By analyzing double mutants we identified interactions of FASCIATA5 gene with LEAFY, APETALA1 and APETALA2, which control the floral meristem identity. The results indicate an important role of gene FASCIATA5 in upregulation of these genes.

[Pleiotropic effect of the fas5 mutation on the shoot development of Arabidopsis thaliana].

The paper described a new mutation that causes the development of multiple meristematic foci as part of shoot apical meristem, which can give rise to new stem axes or cause stem fasciation. The wus-1 mutation represses development of additional apical meristem in fas5 mutant, indicating to the sequential action of the genes in the formation of the shoot apical meristem and FAS5 gene participation in spatial restriction of the WUS gene expression. This function gene FAS5 performs independently of other negative regulators of WUS gene--namely genes CLV, as demonstrated by additive phenotype of double mutants fas5 clv2-1 and fas5 clv3-2. Besides the effect on the development of the shoot apical meristem fas5 mutation causes a change in the shape and number of leaves, accelerates the plant transition to the reproductive stage and leads to the development of cell neoplasms on the stem (buds, stigmatic tissues and ovule-like structures). The mutation also causes changes in apical meristems and leaf cell morphology indicating the activation in cells of DNA endoreduplication. Pleiotropic effect of the fas5 mutation on different stages of ontogeny and different organs suggests that the FAS5 gene plays a complex regulatory role at all stages of the A. thaliana shoot development, and affects many direct or indirect target genes.

[The gene NANA regulates cell proliferation in Arabidopsis thaliana shoot apical meristem without interaction with CLV1, CLV2, CLV3].

A constancycy of stem cell pool in shoot apical meristem of Arabidopsis thaliana is provided by a genetic regulation system with negative feedback loop based on the interaction of the gene WUS, which maintains indeterminate state of cells, with CLV genes, which restrict the level of WUS expression and stem cell pool size. clv mutations lead to an increase in the pool of stem cells in the apical and floral meristems and wus mutation leads to the opposite effect. Mutation na (nana), like wus mutation, causes premature termination of shoot apical meristem function, although it does not affect the activity of the flower meristem. To elucidate the role of NA in the control of shoot apical meristem functioning, the interaction of NA with CLVgenes were investigated. Additive phenotype of double mutants na clv1, na clv1-1, anl na clv3-2 indicates that the NA gene makes an independent contribution to the functioning of the shoot apical meristem. It is assumed that the NA gene controls apical meristem cell proliferation during the transition to the reproductive phase of plant development, acting much later and independently of the genes WUS-CLV.

[Genetic regulation of plant shoot stem cells].

This article describes the main features of plant stem cells and summarizes the results of studies of the genetic control of stem cell maintenance in the apical meristem of the shoot. It is demonstrated that the WUS-CLV gene system plays a key role in the maintenance of shoot apical stem cells and the formation of adventitious buds and somatic embryos. Unconventional concepts of plant stem cells are considered.

[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.

[Interaction between the PINOID/ABRUPTUS gene with the AGAMOUS gene: the negative regulator of stem cells in the meristem of Arabidopsis thaliana flower].

Complementary interaction between the AGAMOUS and PINOID/ABRUPTUS genes was revealed. In double mutant abr ag-1, there is a significant increasing proliferation of cells of the floral meristem and formation of branching bine-like flowers. This data indicate the participation of the PID/ABR gene in limitation of proliferating stem cells of the floral meristem. The revealed increase of transcription level of WUS gene in flowers of the abr mutant, as well as distortion of auxin distribution, allows us to suggest that the PID/ABR gene controls auxin transport and participates in detection of expression domains for the WUS gene.

[Arabidopsis thaliana FIMBRIATA PETIOLES gene, controlling cell division and growth in floral organs].

A new mutant, fimbriata petioles (fip), of Arabidopsis thaliana was obtained by chemical mutagenesis. The mutant is characterized by unusual anomalies of floral organs. Clusters of very large cells formed in the distal region of sepals and petals, which created fringed edges of these organs. An analysis of the morphology of the floral organs and leaves of the fip as 1 double mutant revealed a complementary interaction of the ASYMMETRIC LEAVES1 (AS1) and FIMBRIATA PETIOLES (FIP) genes. It was assumed that the FIP gene, together with the AS1 gene, controls cell proliferation, preventing their premature entry into endocycle.

[Interaction between the ABRUPTUS/PINOID and APETALA1 genes regulating the inflorescence development in Arabidopsis thaliana].

Plant morphology was analyzed in the abr and ap1-1 single mutants, the abr ap1-1 double mutant, and abr mutant plants with extopic expression of the AP1 gene under the control of the 35S RNA constitutive promoter of the cauliflower mosaic virus (abr 35S::AP1). The level of AP1 gene expression was examined in wildtype plants and the abr mutant. The ABR gene was found to interact with the AP1 via dominant epistasis when determining the time of a transition to the reproductive developmental stage and the floral meristem identity. The abr mutant displayed a higher level of AP1 transcription and extended regions of its transcription in leaves and internal whorls of the flowers. Based on these findings, the ABR gene was assumed to play an indirect role in restricting the level and spatial range of AP1 transcription. A complementary interaction of the dominant alleles was observed during floral development, implicating both of the genes in the process.

[Evolution aspects of intraspecific polymorphysm of Arabidopsis thaliana genes coding subunit I of Mg-chelatase complex].

Intraspecific polymorphism in the CHLI 2 gene, coding subunit I of Mg-chelatase complex that forms Mg-protoporphyrin IX was investigated in 19 ecotypes of Arabidopsis thaliana. Sequence divergence by 35 nucleotides was found; 12 of them result into amino acid change in third exon where functional domains of the protein are located. In one of two found divergent sequence haplogroups, Col haplogroup an excess of low-frequency polymorphism was revealed, showing the action of purifying selection and indicating a functional significance of CHLI 2 gene. Paths of evolutionary dynamics for CHLI 1 and CHLI 2 genes determining different forms of subunit I of Mg-chelatase complex of Arabidopsis thaliana are proposed.

[A new Arabidopsis thaliana deletion mutant apetala1-20].

A new deletion allele of the APETALA1 (AP1) gene encoding a type II MADS-box protein with the key role in the initiation of flowering and development of perianth organs has been identified in A. thaliana. The deletion of seven amino acids in the conserved region of the K domain in the ap1-20 mutant considerably delayed flowering and led to a less pronounced abnormality in the corolla development compared to the ap1-3 and apl-6 alleles with low and medium expression, respectively. At the same time, a considerable stamen reduction has been revealed in ap1-20 as distinct from ap1-3 and ap1-6 alleles. These data indicate that the K domain of AP1 can be crucial for the initiation of flowering and expression regulation of B-class genes controlling stamen development.

[Interaction of the BRACTEA gene with the TERMINAL FLOWER1, LEAFY, and APETALA1 genes during inflorescence and flower development in Arabidopsis thaliana].

The major Arabidopsis thaliana genes controlling the shoot architecture are TERMINAL FLOWER1 (TFL1), APETALA1 (AP1), and LEAFY (LFY). The BRACTEA (BRA) gene also codes for one of the key regulators of inflorescence development. The bra tfl1-11, bra lfy-5, and bra ap1-20 double mutants were analyzed morphologically, and expression of the TFL1, AP1, and LFY genes was studied in the bra mutant and wild-type plants. The BRA gene was found to positively regulate the TFL1 and AP1 genes after floral initiation, determining more than 70% of their total expression level. In floral meristem, the BRA gene prevented AP1 expression, restricting AP1 transcription to the perianth zone. Since flowers were completely converted into vegetative shoots in the bra lfy-5 double mutant, it was assumed that the BRA and LFY genes function redundantly and independently in floral initiation. The results demonstrate that BRA is one of the genes that determine the balance between maintenance of proliferative activity in apical meristem and floral development in its peripheral region; such a balance is necessary for indeterminate inflorescence development.

[Genetic control of early stages of leaf development].

The results of studies of genetic regulation of the early leaf morphogenesis, demarcation of the future primordium and transition of cells to determination, have been reviewed. The genetic systems of control of these developmental stages were shown to be conservative and hypotheses of possible mechanisms underlying the evolution of leaf morphology on their basis have been considered.

[Determination of type and spatial pattern formation of flower organs: dynamic model of development].

The mathematical model imitating floral organ spatial pattern formation (positioning) was developed. Computer experiments performed on its basis demonstrated that organ spatial pattern formation in typical crucifer flower occurred in successive order: medial sepals, carpels, lateral sepals, long stamens, petals and short stamens. The positioning was advanced in two directions, acropetally in the perianth and basipetally in the stamens and carpels. The organ type specifying and positioning take place non-simultaneously in different floral areas. The organ type specifying passed ahead of organ primordial spatial pattern formation. The modeling of flower development of several mutants demonstrated that arabidopsis genes AP2 and AG in addition to specifying floral organ types also determine the particular zones in the floral meristem for futur organ development. The AG gene controls the formation of basipetal patterning zones where the reproductive organs develop, AP2 maintains the proliferative activity in the floral meristem that form acropetal patterning zones where perianth organ develop.

[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.