Histological study of embryo-like structures initiated from hypocotyl segments of flax (Linum usitatissimum L.).

Cultivation of flax hypocotyl segments on MS medium supplemented with auxin (2,4-D, NAA) and combination of auxin (NAA) and cytokinin (BAP, zeatin) resulted in production of callus on the cut ends of segments and prolonged cultivation in globular structures resembling early stages of somatic embryos. Embryo-like structures protruded on the surface directly from the subepidermal layers of hypocotyl segments. Despite these globular structures closely resembling somatic embryos, histological observations did not reveal their embryogenic character-organogenesis was the predominant developmental morphogenic pathway. Based on our experiments, as well as on critical revision of existing reports on flax somatic embryogenesis, we conclude, that there has not yet been convincing histological proof of somatic embyogenesis from flax hypocotyl segments.

Expression pattern of transcripts encoding water channel-like proteins in Norway spruce (Picea abies).

With the aim of identifying cells and tissues with high expression of aquaporins (water channels) or homologous genes in Norway spruce (Picea abies), we report the expression patterns of such transcripts in seedlings, in roots of various ages, and in needles. In situ hybridization experiments with a conserved area of a tonoplast intrinsic protein (TIP) gene from P. abies gave high expression signals in differentiating vascular tissues and in the columella cells of the seedling root cap. High-staining signals were also seen in guard cells and in the bundle sheath cells of needles. Moreover, a slightly increased staining signal was seen in cells forming lateral roots as well as in adventitious roots formed from hypocotyl cuttings. By using PCR-based procedures we also identified a full-length aquaporin-like cDNA (mipr) from roots of two-week old seedlings. Sequence homology analysis of the gene suggests that it belongs to the TIP subgroup within the large MIP (major intrinsic protein) family. A phylogenetic analysis of the plant MIP family, including both plasmamembrane (PIP) and tonoplast intrinsic protein (TIP) from Picea, suggests that MIP subgroups evolved already 330 million years ago, as this is the dating of conifer and angiosperm divergence.

Root hair formation: F-actin-dependent tip growth is initiated by local assembly of profilin-supported F-actin meshworks accumulated within expansin-enriched bulges.

Plant root hair formation is initiated when specialized elongating root epidermis cells (trichoblasts) assemble distinct domains at the plasma membrane/cell wall cell periphery complexes facing the root surface. These localities show accumulation of expansin and progressively transform into tip-growing root hair apices. Experimentation showed that trichoblasts made devoid of microtubules (MTs) were unaffected in root hair formation, whereas those depleted of F-actin by the G-actin sequestering agent latrunculin B had their root hair formation blocked after the bulge formation stage. In accordance with this, MTs are naturally depleted from early outgrowing bulges in which dense F-actin meshworks accumulate. These F-actin caps remain associated with tips of emerging and growing root hairs. Constitutive expression of the GFP-mouse talin fusion protein in transgenic Arabidopsis, which visualizes all classes of F-actin in a noninvasive mode, allowed in vivo confirmation of the presence of distinct F-actin meshworks within outgrowing bulges and at tips of young root hairs. Profilin accumulates, at both the protein and the mRNA levels, within F-actin-enriched bulges and at tips of emerging hairs. ER-based calreticulin and HDEL proteins also accumulate within outgrowing bulges and remain enriched at tips of emerging hairs. All this suggests that installation of the actin-based tip growth machinery takes place only after expansin-associated bulge formation and requires assembly of profilin-supported dynamic F-actin meshworks.

Embryogenic culture initiation and somatic embryo development in hybrid firs (Abies alba x Abies cephalonica, and Abies alba x Abies numidica).

Embryogenic cultures were established from silver fir (Abies alba Mill.) female megagametliophytes with developing embryos and from excised mature embryos after pollination with Abies cephalonica Lond. or Abies numidica DeLann pollea The frequency of embryogenic callus formation was dependent on genotype, collection time, medium and explants used. The embryogenic callus initiation potential of megagamethophytes with developing embryos in both hybrids was higher in early July and dropped as the zygotic embryos matured. Excised cotyledonary embryos were less suitable for induction of embryogenic cultures. SH medium supplemented with 1mg/l BAP was the most efficient for callus induction and maintenance. Cultures were composed of early somatic embryos with an embryonal mass formed of highly cytoplasmic cells, rich in cell organelles and a suspensor built up by vacuolated, strongly elongated cells. Maturation of embryos was detected with the formation of bipolar structures with shoot and root apices. Nutrition reserves were observed in cells of embryos cultured on DCR medium containing 1 or 10 mg/l ABA. Cotyledon formation, hypocotyl elongation and low frequency germination occured following transfer of the embryos to the same medium without ABA.

[Postvaccination viremia in breeding flocks of layers and broilers after vaccination against Marek's disease of fowl]. / Postvakcinacní virémie v rozmnozovacích chovech nosných a masných po vakcinaci proti Markove nemoci drubeze.

The immunity state after vaccination against Marek's disease (MD) was studied in three multiplier flocks of laying fowl (MFL), five multiplier flocks of broiler fowl (MFB), and one commercial layer flock (CLF). The occurrence and average titres of post-vaccination viraemia in the selected sets of chickens from these flocks, examined at the age of three or twenty weeks, were used as the immunity criterion. The development of post-vaccination viraemia, following the administration of the MARVAK vaccine at the doses of 100 and 1000 PFU per bird in the HX-SL and Shaver layer hybrids, was examined under laboratory conditions at the same time. In the group of birds examined in the third week of age and coming from the MFL vaccinated with the recommended MARVAK vaccine (dose (100 PFU per bird), 64.3% of the chicks were viraemic, the average viraemia titre being 12 PFU/10(7) leucocytes. After the administration of a four-fold vaccine dose, 57.1% of the chicks were viraemic, the average titre being 3.2 PFU/10(7) leucocytes. After the administration of a ten-fold dose of MARVAK vaccine, 80% of the chicks were viraemic and the average titre of viraemia was 8 PFU/10(7) leucocytes. In the MFB vaccinated with the recommended dose of the MARVAK vaccine, the percentage of viraemic chickens was 48.3% and the average titre of viraemia was 6.5 PFU/10(7) leucocytes. In the pullets examined at the age of 20 weeks the number of viraemic birds ranged from 20 to 50% and the average viraemia titres were from 3.8 to 13.1 PFU/10(7) leucocytes. In the flock affected by acute MD, no post-vaccination viraemia was found in the clinically diseases pullets. In the chickens of the HX-SL line vaccinated with the recommended MARVAK vaccine dose, viraemia culminated in the third week after vaccination (31.5 PFU/10(7) leucocytes), and after the use of the dose ten times as high as the recommended one the culmination came a week later (47 PFU/10(7) leucocytes). In the Shaver chicks vaccinated with the recommended dose or with the ten-fold dose of the MARVAK vaccine, the post-vaccination viraemia culminated in the fourth week after vaccination (94.9 and 116.8 PFU/10(7) leucocytes). The post-vaccination precipitation antibodies were first detected in the eighth week after vaccination.

[Protecting chickens against Marek's disease under laboratory conditions by the administration of Marvak, a Czechoslovak produced vaccine and vaccine imported from East Germany]. / Chránenost kurat proti Markove nemoci v laboratorních podmínkách po aplikaci cs. vakcíny MARVAK a vakcíny dovázené z NDR.

Laboratory trials were conducted to compare the efficiency of two vaccines against Marek's disease (MD) on the basis of the dynamics of post-vaccination viraemia and by means of a challenge test. Two groups of the HX-SL hybrid layers, each containing 40 birds, were vaccinated with the MARVAK cellular vaccine manufactured in Czechoslovakia (100 PFU per chick) or with the Insel Riems vaccine manufactured in the GDR (1000 PFU per chick). In weekly intervals, half the birds of each group were tested for post-vaccination viraemia and the other half, including 20 non-vaccinated birds, were infected by contact with the pathogenic virus of MD from the second day of age. The viraemia in the birds vaccinated with MARVAK culminated in the third week of age when it reached the average value of 25 PFU/10(7) leucocytes; later on, by the eighth week of age, it decreased to 0.62 PFU/10(7) leucocytes. The maximum number of viraemic chicks was found in the third and fourth week of age (80%); on an average it ranged from 60%. The average viraemia in the chickens treated with the vaccine from the GDR ranged from 1.6 to 3.6 PFU/10(7) leucocytes in the second to eighth week of age. A 100% positivity of the tested birds was found in the sixth week of age; it ranged around 70% on an average. In all the challenged groups of birds the precipitation antigen of Marek's disease was detected in feather follicles already 14 weeks from contact infection.(ABSTRACT TRUNCATED AT 250 WORDS)

[Isolation and detection of avian adenoviruses on cell cultures]. / Izolácia a detekcia aviárnych adenovírusov na bunecných kultúrach.

It is important, from the hygienic and epizootological view-point, to detect the presence of various microbiological agents in birds. The authors present the results of the virological examination of poultry, avian adenoviruses being the main object of investigation. Ninety-eight virus strains were isolated from chickens of different age categories and were included in the group of avian adenoviruses according to the form of cytopathic changes on the cell cultures of hen kidneys, according to the need for adaptation passages, chloroform, thermal, and pH resistance, character of nucleic acid, formation of intranuclear inclusions, and joint precipitation antigen, shared with the reference virus.