Embryogenesis is a crucial phase of the plant life cycle, initiated with the fertilization of the... more Embryogenesis is a crucial phase of the plant life cycle, initiated with the fertilization of the zygote and culminated with the formation of a fully developed embryo. The process is executed with defined patterns of cell divisions resulting in the proper formation of the body plan, which is delineated by an apical–basal axis (from cotyledons, to shoot meristem, to hypocotyl, and to root meristem) and a radial axis (epidermis, cortical/ground tissue, and vascular tissue). A well-described and critical event during embryogenesis is the formation of a functional shoot meristem that will generate leaves, stems, and floral structures during postembryonic growth. Genetic studies in Arabidopsis , used as a model system in embryogenesis, have revealed that the establishment of the body plan is governed by an elaborate gene network that ensures the proper execution of the morphogenic events. Experimental perturbations of factors within this network have remarkable implications for the proper formation and functionality of the embryo.
Somatic embryogenesis in plants is a process by which embryos can be produced from somatic cells ... more Somatic embryogenesis in plants is a process by which embryos can be produced from somatic cells cultured under specific conditions. A key initial step is represented by the ability of some cells within the explants to dedifferentiate, i.e., reacquire a “young” or immature state, and then redirect their fate into an embryogenic pathway, demarked by precise changes in gene expression. While the initial morphological patterns of somatic embryo formation can be quite different and difficult to categorize, developing somatic embryos can be assigned similar stages ascribed to zygotic embryos. These similarities allow the utilization of somatic embryogenesis as a model system to investigate physiological and molecular events governing zygotic embryogenesis. The aim of this chapter is to provide a general overview of somatic embryogenesis, by describing and analyzing several in vitro embryogenic systems, and to decipher the molecular network responsible for the generation of somatic embryos.
Mutagenesis via treatment of seeds with chemical mutagens such as ethyl methanesulfonate (EMS) ha... more Mutagenesis via treatment of seeds with chemical mutagens such as ethyl methanesulfonate (EMS) has been widely used for crop improvement. However, this approach is not suitable for some crop species such as clonally propagated crops and allogamous perennial plants characteristically with high levels of genome heterozygosity and a long life cycle. Here, we report direct treatment of in vitro-induced peach shoot tip tissues with EMS for generation of mutations in peach, a perennial, woody fruit tree. We optimized EMS dosage and exposure time and found that treatment of the explants with 0.2 % EMS for 16 h was optimal for generation of genetic variations. So far we have generated nearly 2000 peach seedlings. Typical EMS-induced phenotypic variations were present in the seedlings. Next generation sequencing and subsequent data analyses were performed to monitor the efficiency of mutagenesis. The mutation rate was estimated to be one mutation per 150 kilobase pairs in the mutagenized population, suggesting effectiveness of this method in inducing mutagenesis in peach. Taken together, our data open an avenue for the generation of mutant populations suitable for crop improvement in allogamous perennial plants including fruit trees and clonally propagated plants.
Embryogenesis is a crucial phase of the plant life cycle, initiated with the fertilization of the... more Embryogenesis is a crucial phase of the plant life cycle, initiated with the fertilization of the zygote and culminated with the formation of a fully developed embryo. The process is executed with defined patterns of cell divisions resulting in the proper formation of the body plan, which is delineated by an apical–basal axis (from cotyledons, to shoot meristem, to hypocotyl, and to root meristem) and a radial axis (epidermis, cortical/ground tissue, and vascular tissue). A well-described and critical event during embryogenesis is the formation of a functional shoot meristem that will generate leaves, stems, and floral structures during postembryonic growth. Genetic studies in Arabidopsis , used as a model system in embryogenesis, have revealed that the establishment of the body plan is governed by an elaborate gene network that ensures the proper execution of the morphogenic events. Experimental perturbations of factors within this network have remarkable implications for the proper formation and functionality of the embryo.
Somatic embryogenesis in plants is a process by which embryos can be produced from somatic cells ... more Somatic embryogenesis in plants is a process by which embryos can be produced from somatic cells cultured under specific conditions. A key initial step is represented by the ability of some cells within the explants to dedifferentiate, i.e., reacquire a “young” or immature state, and then redirect their fate into an embryogenic pathway, demarked by precise changes in gene expression. While the initial morphological patterns of somatic embryo formation can be quite different and difficult to categorize, developing somatic embryos can be assigned similar stages ascribed to zygotic embryos. These similarities allow the utilization of somatic embryogenesis as a model system to investigate physiological and molecular events governing zygotic embryogenesis. The aim of this chapter is to provide a general overview of somatic embryogenesis, by describing and analyzing several in vitro embryogenic systems, and to decipher the molecular network responsible for the generation of somatic embryos.
Mutagenesis via treatment of seeds with chemical mutagens such as ethyl methanesulfonate (EMS) ha... more Mutagenesis via treatment of seeds with chemical mutagens such as ethyl methanesulfonate (EMS) has been widely used for crop improvement. However, this approach is not suitable for some crop species such as clonally propagated crops and allogamous perennial plants characteristically with high levels of genome heterozygosity and a long life cycle. Here, we report direct treatment of in vitro-induced peach shoot tip tissues with EMS for generation of mutations in peach, a perennial, woody fruit tree. We optimized EMS dosage and exposure time and found that treatment of the explants with 0.2 % EMS for 16 h was optimal for generation of genetic variations. So far we have generated nearly 2000 peach seedlings. Typical EMS-induced phenotypic variations were present in the seedlings. Next generation sequencing and subsequent data analyses were performed to monitor the efficiency of mutagenesis. The mutation rate was estimated to be one mutation per 150 kilobase pairs in the mutagenized population, suggesting effectiveness of this method in inducing mutagenesis in peach. Taken together, our data open an avenue for the generation of mutant populations suitable for crop improvement in allogamous perennial plants including fruit trees and clonally propagated plants.
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Papers by Mohamed Elhiti