Additional file 7: of Extensive nuclear reprogramming and endoreduplication in mature leaf during floral induction
Best enriched biological process (BP) GO terms for the 24 clusters. The best BP GO term was extra... more Best enriched biological process (BP) GO terms for the 24 clusters. The best BP GO term was extracted with its FDR from each SEA analysis. (XLSX 11 kb)
Plants need to respond quickly and appropriately to various types of light signals from the envir... more Plants need to respond quickly and appropriately to various types of light signals from the environment to optimize growth and development. The immediate response to shading, reduced photon flux (low light), and changes in spectral quality involves changes in gene regulation. In the case of more persistent shade, the plant shows a dramatic change in the organization of chromatin. Both plant responses are controlled via photoreceptor signaling proteins. Recently, several studies have revealed similar features of chromatin reorganization in response to various abiotic and biotic signals, while others have unveiled intricate molecular networks of light signaling towards gene regulation. This opinion paper briefly describes the chromatin (de)compaction response from a light-signaling perspective to provide a link between chromatin and the molecular network of photoreceptors and E3 ubiquitin ligase complexes.
An ultrastructural study on the early development of <i>Zea mays</i> somatic embryos
Canadian journal of botany, Apr 1, 1991
Friable embryogenic callus, obtained from immature embryos of Zea mays L., was cultured on N6 med... more Friable embryogenic callus, obtained from immature embryos of Zea mays L., was cultured on N6 medium supplemented with 1 mg/L 2,4-dichlorophenoxyacetic acid, 6 mM proline, and 2% sucrose. Cultured tissue fragments containing several globular embryoids were excised and examined by light and electron microscopy to follow the early development of maize embryoids. The somatic embryos consist of an apical region and a suspensor region. Cells of the apical region are small, cytoplasm rich, and mitotically active. They contain much starch and numerous bundles of microtubules. Suspensor cells are larger and more vacuolated. A high metabolic activity in both cell types is indicated by the presence of many organelles, coated vesicles, and multivesicular bodies. Transition units appear to form intermediate stages between the embryogenic callus cells and the somatic embryo. A transition unit consists of a group of embryogenic cells and shows an apical and a basal region. The unit has many intercellular spaces, and within the cells areas with organelle-free cytosol are frequently observed. Key words: somatic embryogenesis, in vitro culture, ultrastructure, Zea mays L.
High-resolution FISH reveals the molecular and chromosomal organization of repetitive sequences in tomato
High-resolution fluorescencein situhybridisation (FISH) to pachytene complements and extended DNA... more High-resolution fluorescencein situhybridisation (FISH) to pachytene complements and extended DNA fibres, along with pulse field gel electrophoresis, were used to study the chromosomal distribution and molecular organisation of the telomere repeat (TR) and the tomato-specific subtelomeric repeat (TGR1) in tomato. Pachytene chromosomes were chosen because of their superior resolution as compared to metaphase chromosomes. In addition, chromosomes at this meiotic prophase stage display a clear pattern of distinctive chromomeres and diagnostic heterochromatin blocks along the chromosome arms which enables identification of all bivalents. FISH to extended DNA fibres from lysed leaf nuclei provided a supplementary tool in allowing the reconstruction of physical maps showing the relative positions of both unique and repeated DNA sequences. The most striking result of the FISH study was the detection of a specific molecular organisation of TR with or without adjacent TGR1 sequences. A monosomic addition with tomato chromosome 6 added to tetraploid potato, which was found in the BC2 family of a hexaploid somatic potato (+) tomato hybrid, allowed the assessment of the telomere ends of the tomato chromosome. The integrity of the alien chromosome was tested with fourteen restriction fragments length polymorphism (RFLP) markers covering the entire linkage map of the alien chromosome. Although the presence of all markers could be established, indicating that chromosome 6 was intact, supplementary FISH using total genomic tomato DNA and the tomato-specific TGR1 and TGR2 satellite repeats revealed that the distal 7% of the long arm was replaced by potato chromatin. As expected, FISH to extended DNA fibres revealed red-green tracks for the remaining short arm TR/TGR1 combination and single green tracks for the long arm TGR1 site under the fluorescence microscope. Quantitative analysis of the fluorescing tracks revealed molecular size estimates of 424 kb for the short arm TR/TGRI telomere and 163 kb for the long arm TGRI sites, respectively. Southern analysis of BglIl-and EcoRV- digested high molecular weight DNA, separated by Pulse Field Gel Electrophoresis (PFGE) and using TR and TRG1 as probes, demonstrated a dramatic decrease in TR size and the disappearance ofTGRl sequences in the intergeneric hybrid and the BC1 plant. This unexpected observation could be confirmed by microscopic analysis of TGRI on mitotic metaphase complements showing a clear decrease in TGRI sites. The results of high resolution FISH to extended DNA fibres were also in agreement with the PFGE data showing that telomere repeats in the somatic hybrid and backcross plants are significantly smaller than in the tomato and potato parent. In addition, the combination of long TGRI tracks with adjacent TR tracks, which is typical for tomato telomeres, could not be found in the hybrid and BC1 plants. The results indicate that telomeres in the somatic hybrids become particularly unstable giving rise to breakage of TRs and TR/TGR1 combinations.
Samenvatting References Curriculum vitae General introduction An ultrastructural study on early c... more Samenvatting References Curriculum vitae General introduction An ultrastructural study on early callus development from immature embryos of the maize strains A188 and A632. Cell cycle events during the early period of callus initiation in the scutellum of cultured maize embryos. An autoradiographic study. Cytomorphogenesis of friable embryogénie callus of Zea mays L. An ultrastructural study on the early development of Zea mays L. somatic embryos. Isozymes as biochemical and cytochemical markers in embryogénie callus of Zea mays L. Ultrastructural studies on pollen embryogenesis in maize (Zea mays L.
Page 1. Chromatin Domains and Function Paul Fransz Abstract The inheritance of biological traits ... more Page 1. Chromatin Domains and Function Paul Fransz Abstract The inheritance of biological traits involves not only the transfer of genetic information in the form of DNA, but also epigenetic information. The latter is encrypted ...
Expression pattern of the Arabidopsis thaliana AtEP3 / AtchitIV endochitinase gene
Planta, Mar 19, 2001
The carrot (Daucus carota L.) EP3 chitinase was shown to be essential for somatic embryo formatio... more The carrot (Daucus carota L.) EP3 chitinase was shown to be essential for somatic embryo formation in a carrot mutant cell line. We identified the Arabidopsis thaliana (L.) Heynh. ortholog of the carrot EP3-3 chitinase gene, designated as AtEP3/AtchitIV and analyzed its expression in Arabidopsis by means of reverse transcription-polymerase chain reaction and promoter::beta-glucuronidase and luciferase fusions. As in carrot, the gene is expressed during somatic embryogenesis in &amp;amp;quot;nursing&amp;amp;quot; cells surrounding the embryos but not in embryos themselves. In plants, gene expression is found in mature pollen and growing pollen tubes until they enter the receptive synergid, but not in endosperm and integuments as in carrot. Post-embryonically, expression is found in hydathodes, stipules, root epidermis and emerging root hairs, indicating that the Arabidopsis chitinase may have a function that is not restricted to embryogenesis.
An autoradiographical study of callus initiation in cultured embryos of Zea mays L
Acta botanica neerlandica, 1988
Towards the integration of the physical, genetic and cytogenetic maps in tomato
Samenvatting References Curriculum vitae General introduction An ultrastructural study on early c... more Samenvatting References Curriculum vitae General introduction An ultrastructural study on early callus development from immature embryos of the maize strains A188 and A632. Cell cycle events during the early period of callus initiation in the scutellum of cultured maize embryos. An autoradiographic study. Cytomorphogenesis of friable embryogénie callus of Zea mays L. An ultrastructural study on the early development of Zea mays L. somatic embryos. Isozymes as biochemical and cytochemical markers in embryogénie callus of Zea mays L. Ultrastructural studies on pollen embryogenesis in maize (Zea mays L.
Cell cycle changes were examined in various scutellar regions of immature maize embryos during a ... more Cell cycle changes were examined in various scutellar regions of immature maize embryos during a total culture period of 72 h on a modified MS agar medium containing 1 mg I-1 2,4-D and 6% sucrose. At intervals of 8 h embryos were sampled and transferred to the MS medium supplemented with 5 pCi ml-1 [ 3 H]thymidine and incubated for 8 h. The fraction of labelled nuclei was determined for each interval and a comparison was made between the scutellar regions. During the first day, identical changes in the fraction of labelled nuclei and the mitotic index were observed in all scutellar regions. After the first day, however, various regions showed different cell cycles. The areas from which callus originated were mitotically active, showing high numbers of labelled nuclei, up to 60%. Furthermore, a difference was observed between the adaxial and the abaxial regions concerning the sequence of cell cycle changes. It is concluded that, after the initiation of the in-vitro culture, a shock response and a growth response are manifested, as observed by changes in the cell cycle. These responses proved to be different for the various regions of the immature embryos.
Abbreviations CMT3 CHROMOMETHYLASE3 DDM1 DECREASED IN DNA METHYLATION-1 FLC FLOWERING LOCUS C H3K... more Abbreviations CMT3 CHROMOMETHYLASE3 DDM1 DECREASED IN DNA METHYLATION-1 FLC FLOWERING LOCUS C H3K9 histone H3 at position lysine 9 HD/HDA histone deacetylase HDAC histone deacetylase complex HP1 HETEROCHROMATIN PROTEIN1 KYP KRYPTONITE LHP1 LIKE HETEROCHROMATIN PROTEIN1 MET1 DNA METHYLTRANSFERASE1 PcG Polycomb group SET9 Su(var)39, Enhancer of Zeste, Trithorax SNF2 SUCROSE NON-FERMENTING2 SUV39 SUPPRESSOR OF VARIEGATION39 SWI2 SWITCH2
The effect of 2,4-dichlorophenoxyacetic acid (2,4-D) on the regeneration from hypocotyl protoplas... more The effect of 2,4-dichlorophenoxyacetic acid (2,4-D) on the regeneration from hypocotyl protoplasts of Brassica oleracea was studied by varying the 2,4-D concentration in the protoplast culture medium, 8 p, and the callus proliferation medium, K3. When hypocotyl protoplasts of the inbred line BL12 were cultured in the complete absence of 2,4-D, they divided and produced embryogenic calli. Moreover, these calli generated somatic embryos which were easily recognized by red cotyledons due to the presence of anthocyanin. When 2,4-D was present either in 8p medium or K3 medium the formation of somatic embryos was reduced. On the other hand, the number of shoot-forming calli increased considerably. We therefore conclude that 2,4-D directs the mode of regeneration by suppressing somatic embryogenesis in favour of shoot regeneration. Secondly, 2,4-D increases the regeneration efficiency. Furthermore, the callus proliferation phase on K3 medium is most important with respect to the determination of either somatic embryogenesis or shoot regeneration.
Ultrastructural Studies on Callus Development and Somatic Embryogenesis in Zea mays L
Biotechnology in agriculture and forestry, 1994
Plant regeneration from immature embryos may follow different pathways. First, one may distinguis... more Plant regeneration from immature embryos may follow different pathways. First, one may distinguish between a direct and an indirect way. The former implies the de novo development of meristems on the immature embryo from which new expiants originate. In the case of indirect regeneration, the development of new plantlets from the expiant is interrupted by an intervening callus phase. A second distinction in the regeneration process is made between organo-genesis, or shoot morphogenesis, and somatic embryogenesis. In the case of organogenesis, shoots are formed upon the expiant (directly) or on callus tissue (indirectly). Similarly, somatic embryos may develop directly or indirectly, depending on the absence or presence of an intervening callus phase. Figure 1 shows the different morphogenetic ways of regeneration as observed in embryo cultures of Zea mays (Green and Phillips 1975; Springer et al. 1979; Lu et al. 1982; Armstrong and Green 1985; Vasil et al. 1985; Fransz and Schel 1987). All studies used immature embryos with a scutellum length of 1.5-2 mm, which proved to be a sufficient specification of the required developmental stage. This chapter comprises a structural analysis of these various processes by light and electron microscopy.
Somatic polyploidization is recognized as a means to increase gene expression levels in highly ac... more Somatic polyploidization is recognized as a means to increase gene expression levels in highly active metabolic cells. The most common mechanisms are endoreplication, endomitosis and cell fusion. In animals and plants the nuclei of multinucleate cells are usually prevented from fusing. Here, we report that the nuclei from the syncytial cyst of the chalazal endosperm of Arabidopsis thaliana (L.) Heynh. are polyploid with some intermediate ploidy levels that cannot be attributed to endoreplication, suggesting nuclear fusion. Analysis of isolated nuclei, together with fluorescent in situ hybridization (FISH), revealed that nuclei from the chalazal endosperm are two or three times bigger than the nuclei from the peripheral endosperm and have a corresponding increase in ploidy. Together with the consistent observation of adjoined nuclei, we propose that nuclear fusion contributes, at least in part, to the process of polyploidization in the chalazal endosperm. Confocal analysis of intact seeds further suggested that free nuclei from the peripheral endosperm get incorporated into the chalazal cyst and likely participate in nuclear fusions
This article has been corrected to include a missing funding declaration in the acknowledgements ... more This article has been corrected to include a missing funding declaration in the acknowledgements section and to make an amendment to one other funding source in the same section. No other changes have been made.
Background: The floral transition is a complex developmental event, fine-tuned by various environ... more Background: The floral transition is a complex developmental event, fine-tuned by various environmental and endogenous cues to ensure the success of offspring production. Leaves are key organs in sensing floral inductive signals, such as a change in light regime, and in the production of the mobile florigen. CONSTANS and FLOWERING LOCUS T are major players in leaves in response to photoperiod. Morphological and molecular events during the floral transition have been intensively studied in the shoot apical meristem. To better understand the concomitant processes in leaves, which are less described, we investigated the nuclear changes in fully developed leaves during the time course of the floral transition. Results: We highlighted new putative regulatory candidates of flowering in leaves. We observed differential expression profiles of genes related to cellular, hormonal and metabolic actions, but also of genes encoding long non-coding RNAs and new natural antisense transcripts. In addition, we detected a significant increase in ploidy level during the floral transition, indicating endoreduplication. Conclusions: Our data indicate that differentiated mature leaves, possess physiological plasticity and undergo extensive nuclear reprogramming during the floral transition. The dynamic events point at functionally related networks of transcription factors and novel regulatory motifs, but also complex hormonal and metabolic changes.
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