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1.
The immature zygotic embryos of reciprocal maize hybrids (CHI-31 x GF1 and CHI-31 × GE2) were used as the initial material for induction of somatic embryogenesis in vitro. Histological analysis of somatic embryogenesis revealed high developmental variability. The arising formations were classified into 5 groups: A) somatic embryos phenotypically similar to zygotic embryos, B) polyembryos, C) formations with radicle but without meristematic plumule, D) formations with radicle without differentiated plumule, and E) formations with plumule without radicle. The formatioms A and B regenerated directly into plants. Plant regeneration from formations E required preculture on the rooting medium. Formations C and D failed to develope into plants possibly because of early loss of meristematic cell character during the embryo axis differentiation. The reverse sequence of radicle and plumule differentiation in somatic embryos in comparison with zygotic ones was noted. The epigenetic character of the scutellum, coleoptile, coleorhiza and leaves primordia development was discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

2.
J. Jasik  T. Salajova  J. Salaj 《Protoplasma》1995,185(3-4):205-211
Summary Embryogenic callus cultures of European black pine (Pinus nigra Arn.) were established on megagametophytes containing zygotic embryos in early developmental stage. In addition to many elongated cells and disorganized growing clumps they contained early somatic embryos at various stages of development. At all stages of embryogenesis the embryos were organized as bipolar structures. Cell pairs composed of one isodiametric cell with dense cytoplasm and a second large vacuolated cell were the simplest bipolar system. The vacuolated cell underwent senescence. The cytoplasm-rich cell and its derivates divided transversally, resulting in several cytoplasmic cells arranged in row. An early embryonal cylindrical mass was formed by longitudinal division of the cells in a filament. Proximally localized cells in the early embryonal mass became vacuolized and elongated gradually giving rise to the secondary suspensor. Distal cells remained cytoplasmic in character and formed an embryonal mass along the axis of long early somatic embryos. Differences in the proportion of organelles and heterochromatin clumps, thickness of cell walls and number of plasmodesmata between cells at various stages of early somatic embryogenesis were described.  相似文献   

3.
Hydra is a classical model to study key features of embryogenesis such as axial patterning and stem cell differentiation. In contrast to other organisms where these mechanisms are active only during embryonic development, in Hydra they can be studied in adults. The underlying assumption is that the machinery governing adult patterning mimics regulatory mechanisms which are also active during early embryogenesis. Whether, however, Hydra embryogenesis is governed by the same mechanisms which are controlling adult patterning, remains to be shown. In this paper, in precisely staged Hydra embryos, we examined the expression pattern of 15 regulatory genes shown previously to play a role in adult patterning and cell differentiation. RT-PCR revealed that most of the genes examined were expressed in rather late embryonic stages. In situ hybridization, nuclear run-on experiments, and staining of nucleolar organizer region-associated proteins indicated that genes expressed in early embryos are transcribed in the engulfed "nurse cells" (endocytes). This is the first direct evidence that endocytes in Hydra not only provide nutrients to the developing oocyte but also produce maternal factors critical for embryogenesis. Our findings are an initial step towards understanding the molecular machinery controlling embryogenesis of a key group of basal metazoans and raise the possibility that in Hydra there are differences in the mechanisms controlling embryogenesis and adult patterning.Edited by D. Tautz  相似文献   

4.
Summary Head segments and brains were extirpated from embryos of the tobacco hornworm,Manduca sexta, extracted and the resulting extracts assayed for prothoracicotropic hormone (PTTH) activity on prothoracic glands from day 3 fifth instar larvae and day 0 pupae. Dose-response curves were generated and indicated the presence of PTTH activity in embryonic brains and head segments, suggesting a role(s) for this neurohormone during embryogenesis. Maximal PTTH activity was found in brains from embryos 117 h post-oviposition, just prior to hatching, but activity was also noted in head segments as early as 24 h postoviposition. These data on PTTH and those on ecdysteroids and juvenile hormones in embryos suggest that these 3 classes of hormones which control insect post-embryonic development, may also be involved in the regulation of developmental processes in the embryo.  相似文献   

5.
BACKGROUND: Although centrosomes serve as the primary organizing centers for the microtubule-based cytoskeleton in animal cells, various studies question the requirements for these organelles during the formation of microtubule arrays and execution of microtubule-dependent processes. Using a genetic approach to interfere with centrosomal function, we present an assessment of this issue, in the context of early embryogenesis of the fruit fly Drosophila melanogaster. RESULTS: We identified mutant alleles of the centrosomin (cnn) locus, which encodes a core component of centrosomes in Drosophila. The cnn mutant flies were viable but sterile. The normal course of early embryonic development was arrested in all progeny of cnn mutant females. Our analysis identified a failure to form functional centrosomes and spindle poles as the primary mutant phenotype of cnn embryos. Various aspects of early development that are dependent on cytoskeletal control were disrupted in cnn mutant embryos. In particular, structural rearrangements of cortical microfilaments were strongly dependent on proper centrosomal function. CONCLUSIONS: Centrosomin is an essential core component of early embryonic centrosomes in Drosophila. Microtubule-dependent events of early embryogenesis display differential requirements for centrosomal function.  相似文献   

6.
Hydra's remarkable capacity to regenerate, to proliferate asexually by budding, and to form a pattern de novo from aggregates allows studying complex cellular and molecular processes typical for embryonic development. The underlying assumption is that patterning in adult hydra tissue relies on factors and genes which are active also during early embryogenesis. Previously, we reported that in Hydra the timing of expression of conserved regulatory genes, known to be involved in adult patterning, differs greatly in adults and embryos (Fr?bius, A.C., Genikhovich, G., Kürn, U., Anton-Erxleben, F. and Bosch, T.C.G., 2003. Expression of developmental genes during early embryogenesis of Hydra. Dev. Genes Evol. 213, 445-455). Here, we describe an unbiased screening strategy to identify genes that are relevant to Hydra vulgaris embryogenesis. The approach yielded two sets of differentially expressed genes: one set was expressed exclusively or nearly exclusively in the embryos, while the second set was upregulated in embryos in comparison to adult polyps. Many of the genes identified in hydra embryos had no matches in the database. Among the conserved genes upregulated in embryos is the Hydra orthologue of Embryonic Ectoderm Development (HyEED). The expression pattern of HyEED in developing embryos suggests that interstitial stem cells in Hydra originate in the endoderm. Importantly, the observations uncover previously unknown differences in genes expressed by embryos and polyps and indicate that not only the timing of expression of developmental genes but also the genetic context is different in Hydra embryos compared to adults.  相似文献   

7.
AGL15, a MADS domain protein expressed in developing embryos.   总被引:18,自引:4,他引:14       下载免费PDF全文
To extend our knowledge of genes expressed during early embryogenesis, the differential display technique was used to identify and isolate mRNA sequences that accumulate preferentially in young Brassica napus embryos. One of these genes encodes a new member of the MADS domain family of regulatory proteins; it has been designated AGL15 (for AGAMOUS-like). AGL15 shows a novel pattern of expression that is distinct from those of previously characterized family members. RNA gel blot analyses and in situ hybridization techniques were used to demonstrate that AGL15 mRNA accumulated primarily in the embryo and was present in all embryonic tissues, beginning at least as early as late globular stage in B. napus. Genomic and cDNA clones corresponding to two AGL15 genes from B. napus and the homologous single-copy gene from Arabidopsis, which is located on chromosome 5, were isolated and analyzed. Antibodies prepared against overexpressed Brassica AGL15 lacking the conserved MADS domain were used to probe immunoblots, and AGL15-related proteins were found in embryos of a variety of angiosperms, including plants as distantly related as maize. Based on these data, we suggest that AGL15 is likely to be an important component of the regulatory circuitry directing seed-specific processes in the developing embryo.  相似文献   

8.
Gelatinase A, also called matrix metalloproteinase 2 (MMP-2), belongs to the matrix metalloproteinase (MMP) family. MMP-2 cleaves type IV collagen, denatured collagen (gelatin), and other extracellular matrix (ECM) components. MMP-2 has been reported to be involved in a number of biological and pathological processes, but previous studies have not indicated that its expression is essential for early embryogenesis. In the current study, we have utilized zebrafish as a developmental model to study the role of MMP-2 during embryogenesis. We have successfully isolated a zebrafish MMP-2 (zMMP-2) homologue showing over 80% identity and over 90% similarity to its human counterpart. In situ analysis showed that zMMP-2 was expressed as early as the one-cell stage implying a maternal origin during oogenesis, and embryos continued to express zMMP-2 through at least the 72-h stage of development. RT-PCR analysis confirmed the in situ expression pattern and gelatin zymography indicated that a metalloproteinase with the same gel mobility as vertebrate MMP-2 was present in zebrafish embryos. Injection of zMMP-2 antisense morpholino oligonucleotides into 1- to 4-cell embryos resulted in a truncated axis, monitored through 72 h of development indicating that this metalloproteinase plays an important role in zebrafish embryogenesis. Monpholino-induced alterations in development began to be observed at 12 h of embryogenesis based on morphological and axis marker studies. The results obtained in zebrafish are in contrast to murine knockout studies that indicate that MMP-2 does not have a major role in mouse embryogenesis.Edited by D. Tautz  相似文献   

9.
Activin is a member of the transforming growth factor beta (TGF-beta) and possesses various activities in cellular control phenomena. During Xenopus embryonic development, activin is thought to act as a natural mesoderm-inducing factor. We isolated here the Xenopus activin receptor cDNA from Xenopus tadpole cDNA library and examined the expression of the Xenopus activin receptor gene during the course of early embryonic development. The Xenopus activin receptor has an 87% homology at the level of deduced amino acid sequence with the mouse activin receptor, and using the cDNA obtained, three bands of mRNA with different lengths were detected in Xenopus embryos throughout early embryogenesis. We synthesized activin receptor mRNA in vitro and tested the effect of the injection of the mRNA into Xenopus fertilized eggs on subsequent development. When the synthetic mRNA was injected into uncleaved fertilized eggs, embryos with reduced trunk structure were formed. However, when the mRNA was injected into the ventral blastomeres at the 16-cell stage, embryos with a secondary body axis were formed. These results indicate the importance of the function of activin receptor in the regulatory mechanism for body axis formation.  相似文献   

10.
11.
研究了影响大豆幼胚培养体细胞胚胎发生频率的9个因素。诱导体细胞胚胎发生的适宜幼胚长度为4mm;随着供体植株发育阶段的提高诱导频率下降;最适基本培养基为MS培养基; 蔗糖浓度从1.5%提高到9%,诱导频率逐渐下降;过高的维生素B1浓度对胚胎发生不利;2,4 — D的诱导效果优于NAA,适宜的2,4—D浓度为20ppm; 光、暗处理与生长素种类和浓度之间存在交互作用,接种方式对诱导频率影响很大,体细胞胚只在下表皮与培养基接触的幼子叶的上表皮上产生,当上表皮与培养基接触时,两个表皮都不能产生体细胞胚;被试的所有基因型都能被诱导胚胎发生,不同基因型的诱导频率存在差异。  相似文献   

12.
Yingkun Luo  Hans-Ulrich Koop 《Planta》1997,202(3):387-396
Immature zygotic embryos of six ecotypes (Nd-0, Ler, C24, Col-0, Nossen, Ws-2) of Arabidopsis thaliana (L.) Heynh. were cultured in vitro. The same ecotypes, except Nossen, were used for studies on leaf protoplast culture. Experimental conditions for the induction of somatic embryos were established in both culture systems. In the case of immature zygotic embryos, the parameters investigated were the influence of developmental stage of the explant, the ecotypes used, and various concentrations and combinations of growth regulatory substances (phytohormones). In the ecotype Ler, structures were discovered which were very similar to those found in the early stages of zygotic embryogenesis: globular structures at the end of a suspensor-like single file of cells were frequently observed. In the case of leaf protoplasts, high efficiencies of colony formation and plant regeneration occurred in Ws-2 and C24. A novel type of cell division pattern was found in Col-0 and C24, again highly reminiscent of the early division patterns in zygotic embryos. Similarities and differences between zygotic and somatic embryogenesis are discussed. Received: 2 August 1996 / Accepted: 4 February 1997  相似文献   

13.
植物体细胞胚发生过程中基因表达的研究进展   总被引:2,自引:0,他引:2  
植物体细胞胚胎发生是一个复杂的发育过程,研究者们通过分析植物体细胞胚发生过程中的基因表达或胚性组织和非胚性组织中基因的差异表达,获得了在体细胞胚发生过程不同时期表达的基因,并分析了这些基因在胚胎发生途径中可能的作用。综述了在植物体细胞胚发生过程中细胞周期相关基因、胁迫和激素应答相关基因、信号转导相关基因、晚期胚胎丰富蛋白基因及与体细胞胚发生相关的胞外蛋白基因表达的研究进展。  相似文献   

14.
Rat identical twins were produced from two-cell embryos. In the presence of cytochalasin B, rat two-cell embryos could be separated efficiently into two blastomeres by micromanipulation. Isolated blastomeres, embedded in agar cylinders and cultivated in ligated rat oviducts for 3 days, developed to the morula or blastocyst stage. After removing the agar, pairs of developed one-half embryos were transferred into Day 1 oviducts or Day 4 uteri of pseudopregnant rats. The percentage of embryos, separated either in the presence or absence of cytochalasin B, that developed into live fetuses was higher in cases of uterine transfer than in cases of oviduct transfer (38% vs. 18%, 31% vs. 15%, respectively). Throughout the present experiment, nine pairs of identical twins were successfully produced. This is the first report of the production of identical rat twins by separating two-cell embryos.  相似文献   

15.
We examined the effects of various protease substrates on Xenopus laevis embryogenesis. Thirty-three peptidyl-MCA substrates were added to the culture medium in which Xenopus embryos were developing. Five of the 33 substrates were found to inhibit embryogenesis at the early gastrula stage or much earlier ones. These results suggest that proteases that hydrolyze these substrates are involved in embryonic development. We found that the developmental stage of embryos is crucial for these substrates to inhibit their development. We purified a protease that hydrolyzes Pyr-Arg-Thr-Lys-Arg-MCA, a substrate that inhibits embryogenesis, from Xenopus embryos. This protease turned out to be a component of proteasomes. We found that 4 of the 5 substrates that inhibit embryogenesis are among the proteasome substrates. Thus, we concluded that proteasomes play a crucial role in the development of Xenopus embryos. Possibly, various catalytic subunits in proteasomes function independently, in stage-specific manners.  相似文献   

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18.
The biotechnology of somatic embryogenesis holds considerable promise for clonal propagation and breeding programs in forestry. To efficiently regulate the whole process of plant regeneration through somatic embryogenesis, it is of outmost importance to understand early developmental events when somatic embryos are just formed. In Norway spruce, somatic embryos transdifferentiate from proembryogenic masses (PEMs). This work describes the developmental dynamics (frequency distribution of PEMs and early somatic embryos) of the whole embryogenic suspension culture growing in the presence and absence of plant growth regulators (PGRs), auxin and cytokinin. The experiments have shown that PEM-to-somatic embryo transition is a key developmental switch that determines the yield and quality of mature somatic embryos and ultimately plant production. This switch was induced by the withdrawal of PGRs in cell suspension leading to a rapid accumulation of early somatic embryos (to a maximum of 75% of the entire population of suspension culture) and concomitant degradation of PEMs. The latter was evident from increased level of cell death measured through spectrophotometric Evans blue staining assay. Proembryogenic mass-to-embryo transition and concomitant activation of cell death were mediated by strong extracellular acidification. Therefore, buffering PGR-free culture medium at high (pH 5.8) or low (pH 4.5) levels of pH inhibited both PEM-to-embryo transition and cell death. The yield of mature somatic embryos on abscisic acid (ABA)-containing medium was increased up to 10-fold if the suspension culture had been pretreated for 1 to 9 days in unbuffered PGR-free medium. In this case a large proportion (75%) of the total number of mature embryos was formed within a short, 5-week, contact with ABA. The latter is practically important because prolonged contact with ABA suppresses the growth of somatic embryo plants. Based on these results, an improved method for regulating somatic embryogenesis was set up and tested for nine genotypes of Norway spruce. Over 800 plants regenerated from all tested genotypes demonstrated a good performance in the greenhouse and they were transferred to the field.  相似文献   

19.
大豆主栽品种体细胞胚胎发生的影响因素及再生植株   总被引:11,自引:0,他引:11  
Factors on in vitro somatic embryogenesis of soybean (three elite cultivars) were studied using cotyledons of 3.0-6.0 mm immature seed as explants. Not only the kinds, concentrations and combinations of plant growth regulatory substances but also immature embryo length and inoculum density have main effects on the approaches of embryogenesis. The results of two-factors analysis of variance experiments showed that immature embryo length, plant growth substance concentration and basic medium type have very significant effects on the frequency of embryogenic response, furthermore, interactions exist between the former two factors and are just very significant(at 1% level). The best combinations between 2,4-D concentration and cotyledon length are 10 mg/L 2,4-D & 4.0 mm immature embryos, 20-40 mg/L 2,4-D & 5.0 mm immature embryo. Under these combinations, the salt composition of E1 are very significantly better than that of MS. In conclusion, in the regeneration system established by us the frequency of somatic embryogenesis from the soybean immature cotyledons is greater than 50% and the frequency of conversion of normal (not fused) somatic embryos is about 52.9%-62.6%.  相似文献   

20.
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