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Morpho-histology and genotype dependence of in vitro morphogenesis in mature embryo cultures of wheat.

Delporte F, Pretova A, du Jardin P, Watillon B - Protoplasma (2014)

Bottom Line: Currently, the success of the procedure used to produce transgenic plants is directly proportional to the successful insertion of foreign DNA into the genome of suitable target tissue/cells that are able to regenerate plants.A detailed histological analysis of the chronological sequence of morphological events during ontogeny was conducted.Compared with cultures of immature zygotic embryos, we found that the embryogenic pathway occurs slightly earlier and is of a different origin in our model.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, Bioengineering Unit, Walloon Agricultural Research Centre (CRA-W), Chaussée de Charleroi 234, 5030, Gembloux, Belgium, f.delporte@cra.wallonie.be.

ABSTRACT
Cellular totipotency is one of the basic principles of plant biotechnology. Currently, the success of the procedure used to produce transgenic plants is directly proportional to the successful insertion of foreign DNA into the genome of suitable target tissue/cells that are able to regenerate plants. The mature embryo (ME) is increasingly recognized as a valuable explant for developing regenerable cell lines in wheat biotechnology. We have previously developed a regeneration procedure based on fragmented ME in vitro culture. Before we can use this regeneration system as a model for molecular studies of the morphogenic pathway induced in vitro and investigate the functional links between regenerative capacity and transformation receptiveness, some questions need to be answered. Plant regeneration from cultured tissues is genetically controlled. Factors such as age/degree of differentiation and physiological conditions affect the response of explants to culture conditions. Plant regeneration in culture can be achieved through embryogenesis or organogenesis. In this paper, the suitability of ME tissues for tissue culture and the chronological series of morphological data observed at the macroscopic level are documented. Genetic variability at each step of the regeneration process was evaluated through a varietal comparison of several elite wheat cultivars. A detailed histological analysis of the chronological sequence of morphological events during ontogeny was conducted. Compared with cultures of immature zygotic embryos, we found that the embryogenic pathway occurs slightly earlier and is of a different origin in our model. Cytological, physiological, and some biochemical aspects of somatic embryo formation in wheat ME culture are discussed.

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Regeneration process in wheat mature embryo tissues: somatic embryogenesis—intermediate steps of somatic embryo development. Initiation of cell division 1 DAC (a), small clusters of a few dividing cells. Cell proliferation, first clues apparent 2 DAC (b) and clumps of highly meristematic cells apparent 6 DAC (c). Globular embryo (pre-embryo); a widened globular structure bordered by a well-developed protoderm (the outer unicellular layer, arrowed), clearly delimited from the callus 8 DAC (d). Polar structure without vascular connection with the original tissue 12 DAC; a polarized embryonic structure next to a globular one (e). Bipolar structure, with root meristem differentiation at the basal pole; the organized formation next to this basal part represents the scutellum, indicating a level of further differentiation (f). Bipolar structures, well-organized somatic embryos; in one of the two shown, the vascular connections are visible between the apical and basal poles (arrowed), with a scutellum next to its basal part (g). Three major embryonic tissue systems—shoot apical meristem, root apical meristem, and the differentiation of procambial strands—are visible. In order to better describe post-globular development of the embryo, we have assembled a series of representative pictures of the same object, sequentially ordered, so that different planes can be observed (the different structures appear in different sections because they have not developed in the same plane). DAC days after culture initiation, mes mesocotyl, sc scutellum, ep scutellar epithelium of the original zygotic embryo, pro protoderm, sm shoot meristem, rm root meristem, ap apical pole, bp basal pole, vc vascular connections
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Fig3: Regeneration process in wheat mature embryo tissues: somatic embryogenesis—intermediate steps of somatic embryo development. Initiation of cell division 1 DAC (a), small clusters of a few dividing cells. Cell proliferation, first clues apparent 2 DAC (b) and clumps of highly meristematic cells apparent 6 DAC (c). Globular embryo (pre-embryo); a widened globular structure bordered by a well-developed protoderm (the outer unicellular layer, arrowed), clearly delimited from the callus 8 DAC (d). Polar structure without vascular connection with the original tissue 12 DAC; a polarized embryonic structure next to a globular one (e). Bipolar structure, with root meristem differentiation at the basal pole; the organized formation next to this basal part represents the scutellum, indicating a level of further differentiation (f). Bipolar structures, well-organized somatic embryos; in one of the two shown, the vascular connections are visible between the apical and basal poles (arrowed), with a scutellum next to its basal part (g). Three major embryonic tissue systems—shoot apical meristem, root apical meristem, and the differentiation of procambial strands—are visible. In order to better describe post-globular development of the embryo, we have assembled a series of representative pictures of the same object, sequentially ordered, so that different planes can be observed (the different structures appear in different sections because they have not developed in the same plane). DAC days after culture initiation, mes mesocotyl, sc scutellum, ep scutellar epithelium of the original zygotic embryo, pro protoderm, sm shoot meristem, rm root meristem, ap apical pole, bp basal pole, vc vascular connections

Mentions: In this study, we were able to follow the sequential formation of somatic embryos from their early development (first cellular divisions) to the final step of complete differentiation (Figs. 3 and 4):Fig. 3


Morpho-histology and genotype dependence of in vitro morphogenesis in mature embryo cultures of wheat.

Delporte F, Pretova A, du Jardin P, Watillon B - Protoplasma (2014)

Regeneration process in wheat mature embryo tissues: somatic embryogenesis—intermediate steps of somatic embryo development. Initiation of cell division 1 DAC (a), small clusters of a few dividing cells. Cell proliferation, first clues apparent 2 DAC (b) and clumps of highly meristematic cells apparent 6 DAC (c). Globular embryo (pre-embryo); a widened globular structure bordered by a well-developed protoderm (the outer unicellular layer, arrowed), clearly delimited from the callus 8 DAC (d). Polar structure without vascular connection with the original tissue 12 DAC; a polarized embryonic structure next to a globular one (e). Bipolar structure, with root meristem differentiation at the basal pole; the organized formation next to this basal part represents the scutellum, indicating a level of further differentiation (f). Bipolar structures, well-organized somatic embryos; in one of the two shown, the vascular connections are visible between the apical and basal poles (arrowed), with a scutellum next to its basal part (g). Three major embryonic tissue systems—shoot apical meristem, root apical meristem, and the differentiation of procambial strands—are visible. In order to better describe post-globular development of the embryo, we have assembled a series of representative pictures of the same object, sequentially ordered, so that different planes can be observed (the different structures appear in different sections because they have not developed in the same plane). DAC days after culture initiation, mes mesocotyl, sc scutellum, ep scutellar epithelium of the original zygotic embryo, pro protoderm, sm shoot meristem, rm root meristem, ap apical pole, bp basal pole, vc vascular connections
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4209243&req=5

Fig3: Regeneration process in wheat mature embryo tissues: somatic embryogenesis—intermediate steps of somatic embryo development. Initiation of cell division 1 DAC (a), small clusters of a few dividing cells. Cell proliferation, first clues apparent 2 DAC (b) and clumps of highly meristematic cells apparent 6 DAC (c). Globular embryo (pre-embryo); a widened globular structure bordered by a well-developed protoderm (the outer unicellular layer, arrowed), clearly delimited from the callus 8 DAC (d). Polar structure without vascular connection with the original tissue 12 DAC; a polarized embryonic structure next to a globular one (e). Bipolar structure, with root meristem differentiation at the basal pole; the organized formation next to this basal part represents the scutellum, indicating a level of further differentiation (f). Bipolar structures, well-organized somatic embryos; in one of the two shown, the vascular connections are visible between the apical and basal poles (arrowed), with a scutellum next to its basal part (g). Three major embryonic tissue systems—shoot apical meristem, root apical meristem, and the differentiation of procambial strands—are visible. In order to better describe post-globular development of the embryo, we have assembled a series of representative pictures of the same object, sequentially ordered, so that different planes can be observed (the different structures appear in different sections because they have not developed in the same plane). DAC days after culture initiation, mes mesocotyl, sc scutellum, ep scutellar epithelium of the original zygotic embryo, pro protoderm, sm shoot meristem, rm root meristem, ap apical pole, bp basal pole, vc vascular connections
Mentions: In this study, we were able to follow the sequential formation of somatic embryos from their early development (first cellular divisions) to the final step of complete differentiation (Figs. 3 and 4):Fig. 3

Bottom Line: Currently, the success of the procedure used to produce transgenic plants is directly proportional to the successful insertion of foreign DNA into the genome of suitable target tissue/cells that are able to regenerate plants.A detailed histological analysis of the chronological sequence of morphological events during ontogeny was conducted.Compared with cultures of immature zygotic embryos, we found that the embryogenic pathway occurs slightly earlier and is of a different origin in our model.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, Bioengineering Unit, Walloon Agricultural Research Centre (CRA-W), Chaussée de Charleroi 234, 5030, Gembloux, Belgium, f.delporte@cra.wallonie.be.

ABSTRACT
Cellular totipotency is one of the basic principles of plant biotechnology. Currently, the success of the procedure used to produce transgenic plants is directly proportional to the successful insertion of foreign DNA into the genome of suitable target tissue/cells that are able to regenerate plants. The mature embryo (ME) is increasingly recognized as a valuable explant for developing regenerable cell lines in wheat biotechnology. We have previously developed a regeneration procedure based on fragmented ME in vitro culture. Before we can use this regeneration system as a model for molecular studies of the morphogenic pathway induced in vitro and investigate the functional links between regenerative capacity and transformation receptiveness, some questions need to be answered. Plant regeneration from cultured tissues is genetically controlled. Factors such as age/degree of differentiation and physiological conditions affect the response of explants to culture conditions. Plant regeneration in culture can be achieved through embryogenesis or organogenesis. In this paper, the suitability of ME tissues for tissue culture and the chronological series of morphological data observed at the macroscopic level are documented. Genetic variability at each step of the regeneration process was evaluated through a varietal comparison of several elite wheat cultivars. A detailed histological analysis of the chronological sequence of morphological events during ontogeny was conducted. Compared with cultures of immature zygotic embryos, we found that the embryogenic pathway occurs slightly earlier and is of a different origin in our model. Cytological, physiological, and some biochemical aspects of somatic embryo formation in wheat ME culture are discussed.

Show MeSH
Related in: MedlinePlus