Embryogenesis of the glowworm Rhagophthalmus ohbai Wittmer (Insecta: Coleoptera, Rhagophthalmidae), with emphasis on the germ rudiment formation

The early embryonic development and features of the developing embryo of the glowworm Rhagophthalmus ohbai are described chiefly by light microscopy, with emphasis on the germ rudiment formation and its phylogenetic implication. The egg period is 30-34 days at about 23 degrees C. The newly laid egg is a short ellipsoid, 1.09 by 0.78 mm in size, and the size increases to 1.15 by 0.95 mm by 17 days after oviposition. Cleavage is of the typical superficial type. The germ disk is formed by cell aggregation of the embryonic area at the anterior end of the egg. The central part of the germ disk then sinks into the yolk and the spherical germ rudiment is formed by fusion of the amnioserosal folds extended from all margins of the germ disk. The inner region of the germ rudiment soon becomes slender and develops into the short embryo, whereas the outer region facing the anterior end is extended to form the thin amnion. The embryo then rapidly elongates, the elongation being accompanied by embryo segmentation and formation of appendages. The submerged condition of the embryo persists until about 17 days after oviposition (about 1 day before embryonic revolution) and thereafter the embryo becomes superficial in position. The presence of the following embryonic characters in R. ohbai supports the molecular data placing it within the Lampyridae: 1) formation of a spherical germ rudiment near the anterior end of the egg, and 2) the submerged condition of the developing embryo persists until shortly before revolution.     

Factors affecting direct organogenesis from flower explants of Allium giganteum

A novel method is described for the propagation of Allium giganteum Regel using direct organogenesis resulting in multiple shoot structures formed on mature flower buds or ovaries. A two step induction and differentiation procedure, similar to that described earlier in onion, was tested. Flowers were inoculated on the induction medium for 6 days and extracted ovaries were placed on the differentiation medium. Optimal formation of multiple shoot structures was obtained using modified BDS medium containing 50 g l^–1 sucrose solidified by a mixture of agar/gellan-gum, with 8.88 M benzylaminopurine (BA) and 9.05 M 2,4 dichlorophenoxyacetic acid (2,4-D) in induction medium and 9.08 M tidiazuron (TDZ) in the differentiation medium. Five plant sources obtained from different European retailers of ornamental bulbs were tested separately. All tested genotypes produced multiple organogenic structures, although induction percentages clustered in two distinctive groups. Shoots formed tended to become dormant, and attempts to improve their growth and rooting included treatment with fluridone. Dormancy was partly broken when shoots were briefly dipped in 1 M fluridone. Genetic analysis of plant sources using random amplified polymorphic DNA method showed that 5 retailers actually distribute only two different clones, one of them more and the other less responsive to shoot organogensis.     

Plant regeneration from interspecific hybrid and backcross progeny of Helianthus eggertii × Helianthus annuus

An efficient protocol for plant regeneration from leaves of the interspecific hybrid Helianthus eggertii Small. × Helianthus annuus L. was developed. The regeneration capacity of the first backcross progeny is reported. Leaves from the F1 interspecific hybrid were cultured on Murashige and Skoog basal media (MS) supplemented with -naphthalenacetic acid (NAA), N ⁶-benzyladenine (BA), AgNO₃, KNO₃, casein hydrolysate and adenine sulfate. Embryo-like structures and/or shoots regeneration were observed on most of the tested media. The best results were obtained on media with a higher concentration of cytokinin (8.8 M BA) and lower concentration of auxin (1.08 M NAA). The addition of casein hydrolysate in the media increased the regeneration efficiency. Plant regeneration was achieved via somatic embryogenesis and direct organogenesis. The regeneration potential of leaf, stem and root explants of eighteen first backcross lines was studied. Most of the tested lines were highly regenerable and some of them had DNA content closely related to that of Helianthus annuus L.     

Triazole treatment of explant source provides stress tolerance in progeny of Geranium (Pelargonium hortorum Bailey) plants regenerated by somatic embryogenesis

Thehypothesis that chemically induced stress tolerance in plants can betransferredto a larger clonal population regenerated by somatic embryogenesis wasevaluatedusing the triazole compound paclobutrazol as a chemical inducer of stresstolerance in Geranium (Pelargonium horturum Bailey). Seedswere imbibed in 3.4, 10.2 or 17.0 M (1, 3, 5 mgL^–1) paclobutrazol for 24 h and germinatedfor 7 days. Hypocotyl explants were cultured in vitro toinduce somatic embryogenesis. Plants regenerated from somatic embryos wereexposed to heat stress at 56°C. Explants treated with3.4 M paclobutrazol yielded a substantially higher number ofsomatic embryos compared with untreated explants. In contrast, 17.0M paclobutrazol treatment inhibited embryogenesis producing asignificantly lower number of somatic embryos. There was no difference in theembryo number between control and 10.2 M treatment. Somaticembryos derived from 3.4 and 10.2 M paclobutrazol treatedexplants developed into plants at a faster rate than the control and 17.0M treatments. Plants derived from paclobutrazol-treatedexplants displayed a greater tolerance to heat stress compared with thecontrols. Observations in this study provide a technique for regeneratingplantsin tissue/cell culture with additional desirable traits such as stresstolerancewith minimal chemical contamination of the environment.     

大鼠中脑、内脏和躯体传入在旁巨细胞外侧核神经元的聚合

用细胞外记录的方法观察大鼠巨细胞旁外侧核（ＰＧＬ）对刺激中脑导水管周围背侧部（ｄＰＡＧ）及腹外侧部（ｖＰＡＧ）、腓深神经（ＤＰＮ）、正中神经（ＭＮ）和内脏大神经（ＧＳＰＬ）的反应。这些神经元不仅对某一处刺激部位起反应,而且倾向于对其它任一刺激部位也起反应。８９％（７３／８２）的神经元接受两处或两处以上来源的汇聚投射。６０％（２１／３５）的神经元由于具有压力敏感性,并且其下行投射到脊髓的轴突具有慢的     

Indifference of potato anther culture to colchicine and genetic similarity among anther-derived monoploid regenerants determined by RAPD analysis

Effects of colchicine on androgenesis of diploid potato (Solanum phureja Juz. & Buk.) and ploidy of anther-derived plants were examined in three experiments. In the first, no significant difference was found for mean embryos per anther of an interspecific potato clone after application of five colchicine treatments (0, 25, 50, 100 and 200 mg l^-1) for 24 h to freshly excised anthers containing late uninucleate microspores. The same colchicine treatments were applied to six hybrid potato families in the second experiment. Families differed for number of embryos per anther and embryo regeneration frequency; however, androgenic response did not differ significantly among colchicine treatments. The 312 regenerated plants included 233 (75%) monoploids. The third experiment examined durations (0, 90 s vacuum infiltration, 24, 48 and 72 h) of high colchicine treatment (200 mg l^-1) on anther culture of seedlings representing one family. Mean embryos per anther, though not statistically significant, ranged from 0.96 to 1.90 for 48 h colchicine and 90 s vacuum infiltration, respectively. There were 126 plants regenerated of which 62% were monoploid. Frequency of monoploid plants regenerated from colchicine treatments did not differ significantly. RAPD analysis was conducted on 26 anther-derived monoploids of one family, based on common flasks of origin. The 13 decamer primers revealed 54 polymorphic loci. These were used to characterize the monoploids genetically. From one flask, two pairs of monoploids among six examined were genetically indistinguishable. Examination of a second and third flask revealed, six of seven and three of seven monoploids that were genetically indistinguishable. These data suggest the regeneration of genetic clones within flasks and may indicate the occurrence of secondary embryogenesis during anther culture. This revised version was published online in June 2006 with corrections to the Cover Date.     

Isolation and characterization of a rice homebox gene, OSH15

In many eukaryotic organisms including plants, homeobox genes are thought to be master regulators that establish the cellular or regional identities and specify the fundamental body plan. We isolated and characterized a cDNA designated OSH15 (Oryza sativa homeobox 15) that encodes a KNOTTED-type homeodomain protein. Transgenic tobacco plants overexpressing the OSH15 cDNA showed a dramatically altered morphological phenotype caused by disturbance of specific aspects of tobacco development, thereby indicating the involvement of OSH15 in plant development. We analyzed the in situ mRNA localization of OSH15 through the whole plant life cycle, comparing the expression pattern with that of another rice homeobox gene, OSH1. In early embryogenesis, both genes were expressed as the same pattern at a region where the shoot apical meristem would develop later. In late embryogenesis, the expression pattern of the two genes became different. Whereas the expression of OSH1 continued within the shoot apical meristem, OSH15 expression within the shoot apical meristem ceased but became observable in a ring shaped pattern at the boundaries of some embryonic organs. This pattern of expression was similar to that observed around vegetative or reproductive shoots, or the floral meristem in mature plants. RNA in situ localization data suggest that OSH15 may play roles in the shoot organization during early embryogenesis and thereafter, OSH15 may be involved in morphogenetic events around the shoot apical meristem.     

Polyethylene glycol promotes maturation but inhibits further development of Picea abies somatic embryos

A combined application of abscisic acid (ABA) and high molecular mass osmoticum, polyethylene glycol (PEG) has become a routine method for stimulating somatic embryo maturation in some genera of Coniferales. The goals of the present study were to clarify how the PEG 4000-attributed low osmotic potential (ψ_s) of the maturation medium affects the yield and morphology of mature somatic embryos as well as subsequent developmental processes during germination and ex vitro plantlet growth in different genotypes of Picea abies belonging to 3 full sib seed families. Despite high within- and among-family variation, a stimulatory effect of 7.5% PEG (ψ_s=?0.645 MPa) on somatic embryo maturation was recorded for 13 out of 17 cell lines (F= 2.83, P= 0.1). PEG-treated somatic embryos were more dehydrated than embryos matured in the absence of PEG. Subsequently, embryos were partially desiccated using a high relative humidity treatment (HRH-treatment). The dynamics of embryo water content (WC) during HRH-treatment differed between embryos developed on maturation medium for 5 or 7 weeks. These two patterns remained unchanged irrespective of the ψ_s of the maturation medium. In 5-week somatic embryos, the WC decreased to the lowest level (in the range 25-35%) within the first 8 days of HRH-treatment and was not further substantially changed. Seven-week embryos also lost water within 8 to 16 days (decrease to 15-25% WC), but this drop was followed by rehydration of embryonic tissues by 24th day of HRH-treatment up to nearly the initial WC. Thus, 7-week embryos experienced both desiccation and slow imbibition in the course of the 24-day HRH-treatment. This could account for their increased germinability compared to 5-week somatic embryos found in the present study. Addition of 7.5% PEG to the maturation medium significantly inhibited somatic embryo germination for the vast majority of genotypes (F= 7.35; P= 0.01). Moreover, even after ex vitro transfer, both radicle elongation and lateral root formation were substantially suppressed (F= 3.8; P= 0.03) in those plantlets produced from PEG-treated somatic embryos. Alterations both in the organization of the root meristem and in the structure of the root cap were found by histomorphological analysis of PEG-treated somatic embryos. All those embryos possessed massive root caps with numerous intercellular spaces in the pericolumn tissue. Cells of the quiescent center exhibited clear symptoms of degradation manifested in shrinkage and collapse of the protoplasm. In addition, PEG-treated embryos were of smaller size compared to embryos matured without osmoticum. When grown in artificial substrate (up to 5 months) the PEG-induced inhibitory post-effect gradually decreased. At this stage, the duration of maturation was the only factor separating plantlets into slow- and fast-growing categories. Somatic embryos matured for 5 weeks produced plantlets twice the size of those produced by 7-week embryos (F= 37.8; P < 0.0001). This trend did not depend on ψ_s of the maturation medium, nor on the genotype.