Here we report the consequences of telomere erosion in Arabidopsis thaliana, studied by examining seed and pollen production and the course of male meiosis through the last five generations (G5-G9) of telomerase-deficient Arabidopsis mutants. We used a previously described mutant line in which telomerase activity was abolished by T-DNA insertion into the TERT gene encoding telomerase reverse transcriptase. Reduced fertility accompanied by morphological abnormalities occurred in G6, which produced on average 35 seeds per silique (vs. 43 in wild type) and worsened in G7 (30 seeds) and G8 (14 seeds), as did the morphological abnormalities. The last generation of tert mutants (G9) did not form reproductive organs. Analysis of meiosis indicated that the main cause of reduced fertility in the late generation tert mutants of Arabidopsis was the numerous chromosomal end-to-end fusions which led to massive genome rearrangements in meiocytes. Fusion of meiotic chromosomes began in G5 and increased in each of the next generations. Unpaired chromosomes (univalents) were observed in G7 and G8. The study highlights some differences in the meiotic consequences of telomere shortening between plant and animal systems.
The chemical composition and bioactivity of a water/methanol extract prepared from aerial parts of Circaea lutetiana were determined. HPLC-DAD-MS3 analysis revealed the presence of 14 different compounds comprising phenolic acids, ellagitannins and flavonoids. Antioxidant assays showed the extract's strong scavenging activity towards DPPH (SC50 33.1±3.1 μg/ml), O2 - (SC50 4.0±2.3 μg/ml) and H2O2 (SC50 below 2 μg/ml). Enzyme-based studies revealed that Circaea lutetiana extract inhibits the activity of hyaluronidase (IC50 13.3±2.4 μg/ml) and lipoxygenase (IC50 44.7±1.4 μg/ml). These results support some traditional uses of Circaea lutetiana.
The effects of gamma irradiation on the vernalization requirements, growth and development of winter wheat grown in a rainout shelter were studied during two successive growing seasons. Dry grains of winter wheat cv. Kobra were irradiated with 300 Gy radiation from a cobalt 60 gamma irradiator. Treated and control grains were pregerminated and subjected to vernalization for 0, 42 or 54 days. Morphological parameters of the plants developing from irradiated seeds (M1 generation) and the plants grown from the seeds produced by the irradiated plants (M2 generation) were measured in order to track the studied effects over two generations. Irradiation of dry grains slowed the growth and development of the plants regardless of the temperature treatment. The measured yield structure elements appeared to be lower for irradiated plants, but no clear effect of radiation on vernalization requirements was noted
Achene macro- and micromorphology and pericarp anatomy are described in four Polish species of Anemone (A. narcissiflora, A. nemorosa, A. ranunculoides, A. sylvestris). Biometric analysis showed that achene size varies greatly in all the studied species and is of limited diagnostic value. Three types of sculpture connected with the character of the indumentum were distinguished. The presence or absence of stomata on the achene style and the character of the hair base differentiated A. nemorosa and A. ranunculoides, which have the same type of pericarp ornamentation. The endocarp (number of layers and outline of its cells) was shown to be useful in the systematics of Anemone
The Arabidopsis CDKG;2 gene encodes a putative cyclin-dependent Ser/Thr protein kinase of unknown biological function. This gene shows structural similarity to animal and human cyclin-dependent (PITSLRE) kinases. This study used the homozygous knockout cdkg;2 mutant based on T-DNA insertional line SALK_090262 to study the effect of mutation of the CDKG;2 gene on explant response and in vitro plant regeneration. For callus induction and proliferation, hypocotyls and cotyledons of 3-day-old seedlings of cdkg;2 and A. thaliana ecotype Col-0 were cultured on solid MS medium supplemented with 2,4-D (2 mg l-1). Organogenesis was induced after callus transfer on MS + TDZ (0.5 mg l-1). The initiation time of callus and shoot induction differed between the mutant and control cultures. Shoot regeneration after callus transfer on MS + TDZ was delayed in cdkg;2 (31 days versus 7 days in Col- 0). Shoots formed on callus derived from Col-0 hypocotyls but not on cotyledon-derived callus; in cdkg;2, shoots developed on both callus types. Mutant shoots did not form roots, regenerants were dwarfed, and inflorescences had small bud-like flowers with a reduced corolla and generative organs. Abnormalities observed during cdkg;2 organogenesis suggest a role of CDKG;2 as a regulator of adventitious root initiation
Isozyme, RAPD and AFLP markers were evaluated and compared for their ability to determine genetic similarity in a set of 18 parental lines of winter oilseed rape F<sub>1</sub> hybrids developed using CMS ogura. Five isozyme systems, 64 RAPD starters and 23 EcoRI+3/MseI+3 AFLP primer combinations generated 597 polymorphic markers. These polymorphic fragments were chosen for estimation of genetic similarity. Of the total number of polymorphic products, polymorphic zymograms constituted only 3.0% of the markers, 57 RAPD primers 37.7%, and 23 AFLP primer combinations 59.3%. The size of RAPD polymorphic products ranged from 564 to 2100 bp. On average there were four amplified bands per primer, with 61.0% polymorphism. The AFLP polymorphic fragments ranged from 72 to 1352 bp in size. AFLP assays generated 15 bands per primer pair on average and detected roughly four times more bands than with RAPD analysis. The genetic similarity coefficients based on all marker data range from 0.52 to 0.84. The correlation of genetic similarities based on RAPD and AFLP markers was 0.58. Estimated genetic similarity based on isozyme data was not correlated with genetic similarity derived from the two DNA-based markers. The dendrogram constructed with the three types of markers taken together grouped all the winter oilseed rape parental lines into several similar clusters. The genomic distribution and frequency of the RAPD and AFLP markers can serve well as estimators of genetic similarity between parental lines of F<sub>1</sub> CMS ogura hybrids
The study assessed the effect of cumulative tropospheric ozone on the morphology of an ozone-sensitive (Bel W3) and an ozone-resistant (Bel B) tobacco cultivar, and two petunia cultivars (Mirage, White Cascade). The plants were exposed at two sites differing in tropospheric ozone level for two months during the 2008 growing season. Similar sets of plants were cultivated in control conditions. Morphological parameters of the plants were measured every week during the experiment. The correlation between the recorded results and the cumulative concentrations of tropospheric ozone measured at the two exposure sites was estimated. The ozone-sensitive tobacco cultivar showed increased visible damage after four weeks of the experiment, although ozone was relatively low during the preceding weeks, possibly confirming the cumulative effect of ozone on the plant response. The ozone-resistant tobacco cultivar showed higher mean plant growth and leaf growth than the ozone-sensitive one throughout the experimental period, but at the exposure sites the ozone-sensitive cultivar showed plant growth similar to or higher than the controls, especially at the forest site where ozone concentrations were higher. This suggests a plant defense against reduction of leaf assimilation area (i.e., against leaf necrosis). Petunia cv. Mirage showed lower growth at the control site and had fewer flowers than White Cascade at all sites. White Cascade had more flowers than Mirage in the last week of the experiment at the forest site where tropospheric ozone was higher. Its mean growth was higher at the forest site than at the other exposure site
Light exposure is an important environmental factor which breaks seed dormancy in many plant species. Phytochromes have been identified as playing a crucial role in perception of the light signal that releases seed germination in Arabidopsis. Phototropins (Phot1, Phot2) are blue/UV-photoreceptors in plants which mediate phototropic responses, chloroplast relocation, hypocotyl growth inhibition and stomata opening. We studied germination under different light conditions in Arabidopsis Phot1-null and Phot2-null mutants and in a double phot1phot2 mutant. Germination of single phot1 and phot2 mutants in darkness was much lower than in wildtype (WT) seeds, whereas double phot1phot2 mutant lacking both functional phototropins germinated at frequency comparable to WT seeds, irrespective of light and temperature conditions. Light treatment of imbibed seeds was essential for effective germination of phot1, irrespective of low-temperature conditioning. In contrast, cold stratification promoted dark germination of phot2 seeds after imbibition in dim light. Low germination frequency of phot1 seeds under low light intensity suggests that the presence of functional Phot1 might be crucial for effective germination at these conditions. The lower germination frequency of phot2 seeds under continuous light suggests that Phot2 might be responsible for stimulating germination of seeds exposed to direct daylight. Thus, the phototropin system may cooperate with phytochromes regulating the germination competence of seeds under different environmental conditions
An efficient micropropagation system for Taraxacum pieninicum using seedling explants germinated in vitro is described. Shoot tips and fragments of cotyledons, hypocotyls and roots were isolated from several-day-old seedlings. The highest response, 100% frequency with 12.3 axillary shoots/explant, was from shoot tips on medium supplemented with 0.5 mg L-1 BA and 0.05 mg L-1 NAA. In subsequent subcultures the number of shoots was significantly higher on all explants cultured on medium containing 0.25 and 0.5 mg L-1 BA, and the multiplication rate was highest (20 shoots/explant) in the 4th passage. Shoots rooted on MS and 1/2 MS medium; the highest rooting frequency was 90% and the highest number of roots 2.7/shoot. Rooted plants showed 96.2% survival in sterile soil:sand, and 100% survival in hydroponic culture. Regenerated plants flowered in the second year after acclimatization and yielded viable seeds. This protocol for obtaining complete plants through micropropagation may prove useful for conservation of the genetic resources of this and other endangered species
Hylocereus undatus flower is commonly used as food or for medicinal purposes in south China. To study its antioxidant activity and mechanism we used antioxidant and chemical assays to compare two commercial samples from different locations (Shenjing, Qixing). The difference in antioxidant levels corresponded with differences in chemical content (including total phenolics, total flavonoids, kaempferol and quercetin) between Shenjing and Qixing. The antioxidant ability of H. undatus flower seems attributable to total phenolics (mainly total flavonoids). Kaempferol is one of the main bioactive components. H. undatus flower exerts its antioxidant effects through metal chelation and radical scavenging via hydrogen atom (H•) and electron (e) donation.
The systematic position of Sorbus population occurring in the Pieniny Mts. is controversial. To verify its taxonomic status we studied the ITS sequence of closely related species of the S. aria group: Sorbus sp. from the Pieniny Mts., S. aria from the Tatra Mts., S. graeca from the Balkans, and other well-distinguished native Polish Sorbus species (S. aria, S. aucuparia, S. intermedia and S. torminalis). As a reference we examined Sorbus populations closest to the Pieniny Mts. where S. graeca was reported to occur, in Slovakia. The results indicate that the Sorbus plants found in the Pieniny Mts. differ genetically from those in the Tatra Mts. but are identical to those collected from the Vihorlat Mts. in Slovakia and are closely related to S. graeca from the Balkans
We examined the effects of feeding by the polyphagous insect Coccus hesperidum on its host plant Nephrolepis biserrata under different intensities of infestation. As an effect of scale insect feeding there were significant changes in the values of parameters reflecting the state of cell membranes. N. biserrata plants reacted to the biotic stress by increasing guaiacol peroxidase activity and decreasing catalase activity. Our data show that these processes play key roles in plant tolerance mechanisms, here the fern’s response to insect feeding. The observed complex reaction of N. biserrata testifies to actively proceeding, complex and very often contrasting mechanisms triggered with the aim of neutralizing the effects of biotic stress and enabling normal cell functioning in plants attacked by scale insects
We examined the development of the endosperm chalazal haustorium of Rhinanthus serotinus, using histochemical assays and light and electron microscopy. The chalazal haustorium is a huge single cell containing two enlarged nuclei. The nuclei are located in the middle of the haustorium cell. At the chalazal end of the haustorium cell structure, ultrastructural study revealed the presence of a transfer wall forming wall ingrowths. At all examined stages of haustorium cell development we identified insoluble polysaccharides, proteins, nucleic acids and lipid droplets. Macromolecules were especially abundant in the fully differentiated haustorium cell. Our results suggest that the endosperm chalazal haustorium is a site of intense metabolic activity
The paper reports a comparative study of the female gametophyte and especially synergid structure in sexual and apomictic dandelions. We analyzed diploid sexually reproducing Taraxacum linearisquameum (2n = 2x = 16) and two triploids, T. alatum and T. udum (2n = 3x =24), with autonomous embryo and endosperm development. There were no observed differences in the organization of the mature megagametophyte between the examined species. Both meiotically reduced and diplosporous embryo sacs showed typical polarity of the egg apparatus cells, together with development of a filiform apparatus in the synergids, but immunocytochemical analyses indicated that microtubules form longitudinal brush-like bundles adjacent to the filiform apparatus in the synergids of the sexual T. linearisquameum. This arrangement of cytoskeletal elements is similar to the configuration described in other amphimictic plants. The synergids of the apomictic T. alatum and T. udum show a uncharacteristic and relatively weak cytoskeleton with no brush-like bundles. We discuss the role of synergids in autonomous apomicts.
Aconitum lasiocarpum (Carpathian endemic) and A. variegatum (European endemic) occur sympatrically in the Polish Western Carpathians. Here their taxonomic hybrid A. ×pawlowskii occurs. The aim of this study was to determine the relationship between the taxonomic (Linnaean approach) and genetic structure (PCR-ISSR analysis) of the populations and individuals in two allopatric and four sympatric populations. We determined 309 individuals (OTUs) to species, subspecies and nothospecies using the Linnaean system of classification, and then genetically fingerprinted 39 randomly chosen OTUs. Comparison of the Nei and Li distances obtained from ISSR and morphological matrices using the Mantel test indicated a significant correlation (n = 39, r = 0.53, P = 0.001). Genetic analysis (NEWHYBRIDS) pointed to 7 OTUs as being later-generation hybrids (B1 introgessants) in the sympatric area. Five of them belong to A. variegatum, indicating cryptic introgression, and two belong to A. ×pawlowskii. Nonmetric multidimensional scaling (NDMS) showed gene flow between A. lasiocarpum and A. ×pawlowskii. Allopatric, morphologically pure A. lasiocarpum and A. variegatum populations differed significantly in their ISSR profiles (Fischer's R×C test, P < 0.0001). Expected heterozygosity (Hj) was significantly (p=0.05) lower in allopatric (0.1261-0.1268) than in sympatric populations (0.1348-0.1509), indicating a genetic melting pot in sympatry. The results support the existence of a natural interspecific hybrid swarm zone in the sympatric area of occurrence of Aconitum, and the taxonomic circumscription of the nothospecies within the Linnaean taxonomic system
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