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.
Highlights
With few exceptions, plant genetic engineering requires using molecular biology tools along with the technology for gene transfer into the plant genomic DNA, combined with robust protocols allowing whole plants to be regenerated from the genetically modified cells
In this study, drawing on a previously described protocol for somatic embryogenesis induction established from wheat mature embryo (ME) culture, (i) the competence of ME tissues for tissue culture and morphogenesis was documented, (ii) genotypic variation at each step of the regeneration process was evaluated through varietal comparison, and (iii) a detailed histological study of the oncogenesis involved in plant neoformation was conducted
This paper has described a histological study of T. aestivum L. somatic embryo formation, from their first cellular divisions to the last step of their complete development, passing through a chronological series of characteristic morphological stages
Summary
Plant genetic engineering requires using molecular biology tools along with the technology for gene transfer into the plant genomic DNA, combined with robust protocols allowing whole plants to be regenerated from the genetically modified cells. In vitro plant regeneration techniques and models are widely used as large-scale propagation tools and case studies for basic research in plant development, as well as in response to environmental factors. “Expression of the embryogenic/organogenic potential only occurs if cells within the explant are ‘competent’ or responsive to specific culture cues which allow them to differentiate into embryos or organs” (Elhiti and Stasolla 2011). Factors such as age, ontogenic and physiological conditions, and the degree of differentiation affect the response of the explants to in vitro culture conditions
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