Direct somatic embryogenesis from axes of mature peanut embryos

Summary Plant regeneration via somatic embryogenesis was obtained in peanut (Arachis hypogaea L.) from axes of mature zygotic embryos. The area of greatest embryogenic activity was a 2-mm region adjacent to and encircling the epicotyl. Somatic embryogenesis was evaluated on Murashige and Skoog media supplemented with a variety of auxin treatments. Maximum production occurred on medium supplemented with 3 mg · liter⁻¹ 4-amino-3,5,6-trichloropicolinic acid. Explant cultures were transferred to half-strength medium supplemented with 1 mg · liter⁻¹ gibberellic acid for somatic embryo germination and early plantlet growth. Plantlets, transferred to soil, were placed in a greenhouse and grown to maturity.     

Rapid multiplication of Polyscias filicifolia by secondary somatic embryogenesis

Efficient plant regeneration through somatic embryogenesis was achieved in Polyscias filicifolia. Embryogenic calluses were induced on Murashige and Skoog (MS) basal medium supplemented with 0.5 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.0 mg l⁻¹ benzylaminopurine (BAP; type I callus) and on MS medium with 2.0 mg l⁻¹ 2,4-D and 0.01 mg l⁻¹ kinetin (type II callus) from leaf explants of a 2-yr-old plant. Primary somatic embryos (PSEs) developed after four passages of suspension culture established from embryogenic callus when cultured in liquid half-strength MS medium (1/2 MS) without growth regulators. PSEs in the cotyledonary stage were multiplied by adventitious embryogenesis. Single secondary somatic embryos (SSEs) or their clusters developed at the base of PSE hypocotyls and regenerated into plantlets in a one-step process on plant growth regulator-free 1/2 MS medium. Low sucrose concentration of 15 g l⁻¹ promoted development of normal SSEs. All SSEs regenerated into single, well-rooted plantlets on a Nitsch and Nitsch medium supplemented with 0.5 mg l⁻¹ kinetin, 0.1 mg l⁻¹ indole-3-butyric acid, and 10 mg l⁻¹ adenine sulfate. Subsequent two subculture cycles on the same medium were necessary to obtain plantlets sufficiency developed to allow successful transfer to the soil. Rooted plantlets were established in a peat mixture with 90% survival, with the plants showing normal morphological characteristics.     

Maturation and persistence of the anti-SARS-CoV-2 memory B cell response

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Germplasm Modification and Its Potential for Finding New Sources of Resistance to Diseases

In vitro procedures are playing a major role in plant breeding. Embryo rescue, either through the culture of excised embryos derived from incompatible crosses or by means of ovule culture, has been a standard procedure for the introgression of genes conferring disease resistance into economically important plants. Somatic hybridization (i.e., protoplast fusion) has also been demonstrated to have some potential in obtaining hybrids that result from very wide interspecific and intergeneric crosses. Wide crosses have also been achieved by means of in vitro pollination of excised ovaries or ovules. Tissue culture-induced variability in regenerated plant (i.e., somaclonal variation) appears to be an effective way of obtaining undirected genetic change that can enhance disease resistance and yield and alter the growth habit of crops that are normally propagated vegetatively (e.g., potato) or by seed (e.g., tomato). In the near future, the isolation and sequencing of genes that confer resistance to specific plant pathogens will be possible, and transfer of this information between species will become a reality.     

Study of the late embryogenesis of Daphnia (Anomopoda, ‘Cladocera’, Branchiopoda) and a comparison of development in Anomopoda and Ctenopoda

The embryonic development of Daphnia galeata and D. hyalina (`Cladocera', Anomopoda, Daphniidae) has been investigated by observing living embryos removed from female brood pouches. The sequence of morphological changes was analysed, as was the time at which the activity of certain organs began. The timing of these events at 22 °C is documented for both species.These data were compared with similar information, previously obtained for two representatives of the Ctenopoda (Kotov & Boikova, 1998). The sequence of events is basically similar in the two groups during early and late phases of their development, but the time of shedding of the embryonic membranes is different in the Anomopoda and Ctenopoda. The ctenopod embryo hatching from the second egg membrane is covered by the third membrane, which will be cast some hours later. The anomopod embryo hatches from the second egg membrane approximately simultaneously with the shedding of the third membrane, and it is covered already by the fourth membrane after the shedding of the second egg membrane.Earlier (Kotov & Boikova, 1998), we determined four embryonic instars in the course of the development of the Ctenopoda. Two of them are passed within the egg membranes, the next two instars occur after the shedding the egg membranes within the mother's brood pouch. However, in anomopods, one of the latter (the third) occurs within the second egg membrane, one is incorporated into the egg. Thus, the development of the Anomopoda is more embryonized in comparison with that of the Ctenopoda.     

Appearance and Differentiation of NADPH-D-Neurons in Ontogeny of Cerebral Cortex in Rats

The appearance of presumptive NO-ergic nerve cells and their differentiation in the rat neocortex were studied. For this purpose, a comparative analysis of the development and differentiation of NADPH-D-positive neurons in the neocortex transplants taken from the embryos of different ages and transplanted in the occipital cortex of adult rats and in the normally developing cerebral cortex was undertaken. The nervous tissue was stained histochemically for NADPH-D. The results we obtained suggest that no NADPH-D-containing neurons were found in the transplants from 15-day embryos, while they developed in those from 18-day embryos. Hence, precursors of NO-ergic neurons were still absent in the presumptive neocortex of 15-day embryos and appeared only on day 16–18 of embryogenesis. Expression of NADPH-D begins in them only within four to five days, but the neurons are differentiated during a relatively short period of time. Most NADPH-D-positive neurons reach their structural–functional maturity already by the end of the first week of postnatal development, while their complete maturation takes place by the end of the second week of postnatal development.     

Separation of precultured pollen from Nicotiana tabacum by aqueous polymer two-phase partition

Pollen isolated from cold treated and precultivated anthers of tobacco (Nicotiana tabacum L. var. Wisconsin 38) were separated into different fractions with counter-current distribution using an aqueous Dextran-polyethylene glycol two-phase system. It was possible to distinguish among eight pollen classes differing in developmental stage and in partitioning. A part of each fraction was cultivated for analysis of embryo formation. This was highest in a fraction with an intermediate to high partition in the phase system. Enriched in this fraction were also pollen that were fairly well stained with acetocarmine, contained several nuclei and had a relatively low mitochondrial activity. The enrichment of embryogenic pollen offers several advantages especially to physiological studies on embryogenesis.     

Adaptations for matrotrophy in the female reproductive system in the pseudoscorpion Chelifer cancroides (Chelicerata: Pseudoscorpiones,Cheliferidae)

Pseudoscorpiones (pseudoscorpions, false scorpions) is an order of small terrestrial chelicerates. While most chelicerates are lecithotrophic, that is, embryos develop due to nutrients (mostly yolk) deposited in the oocyte cytoplasm, pseudoscorpions are matrotrophic, that is, embryos are nourished by the female. Pseudoscorpion oocytes contain only a small amount of yolk. The embryos develop within a brood sac carried on the abdominal site of the female and absorb nutrients by a pumping organ. It is believed that in pseudoscorpions nutrients for developing embryos are produced in the ovary during a postovulatory (secretory) phase of the ovarian cycle. The goal of our study was to analyze the structure of the female reproductive system during the secretory phase in the pseudoscorpion Chelifer cancroides, a representative of the family Cheliferidae, considered to be one of the most advanced pseudoscorpion taxa. We use diverse microscopic techniques to document that the nutritive fluid is produced not only in the ovaries but also by the epithelial cells in the oviducts. The secretory active epithelial cells are hypertrophic and polyploid and release their content by fragmentation of apical parts. Our observations also indicate that fertilization occurs in the oviducts. Moreover, in contrast to previous findings, we show that secretion of the nutritive material starts when the fertilized oocytes reach the brood sac and thus precedes formation of the pumping organ. Summing up, we show that C. cancroides exhibits traits of advanced adaptations for matrotrophy due to coordinated secretion of the nutritive fluid by the ovarian and oviductal epithelial cells, which substantially increases the efficiency of nutritive fluid formation. Since the secretion of nutrients starts before formation of the pumping organ, we suggest that the embryos are able to absorb the nutritive fluid also in the early embryonic stages.