Abstract
BackgroundIn Quercus suber, cork oak, a Mediterranean forest tree of economic and social interest, rapid production of isogenic lines and clonal propagation of elite genotypes have been achieved by developing in vitro embryogenesis from microspores and zygotic embryos respectively. Despite its high potential in tree breeding strategies, due to their recalcitrancy, the efficiency of embryogenesis in vitro systems in many woody species is still very low since factors responsible for embryogenesis initiation and embryo development are still largely unknown. The search for molecular and cellular markers during early stages of in vitro embryogenesis constitutes an important goal to distinguish, after induction, responsive from non-responsive cells, and to elucidate the mechanisms involved in embryogenesis initiation for their efficient manipulation. In this work, we have performed a comparative analysis of two embryogenesis pathways derived from microspores and immature zygotic embryos in cork oak in order to characterize early markers of reprogrammed cells in both pathways. Rearrangements of the cell structural organization, changes in epigenetic marks, cell wall polymers modifications and endogenous auxin changes were analyzed at early embryogenesis stages of the two in vitro systems by a multidisciplinary approach.ResultsResults showed that early embryo cells exhibited defined changes of cell components which were similar in both embryogenesis in vitro systems, cellular features that were not found in non-embryogenic cells. DNA methylation level and nuclear pattern, proportion of esterified pectins in cell walls, and endogenous auxin levels were different in embryo cells in comparison with microspores and immature zygotic embryo cells from which embryos originated, constituting early embryogenesis markers.ConclusionsThese findings suggest that DNA hypomethylation, cell wall remodeling by pectin esterification and auxin increase are involved in early in vitro embryogenesis in woody species, providing new evidences of the developmental pattern similarity between both embryogenesis pathways, from microspores and immature zygotic embryos, in woody species.
Highlights
In Quercus suber, cork oak, a Mediterranean forest tree of economic and social interest, rapid production of isogenic lines and clonal propagation of elite genotypes have been achieved by developing in vitro embryogenesis from microspores and zygotic embryos respectively
Tree breeding strategies have focused on ways to reduce cycle time and improve the efficiency of selection; here, propagation of selected trees by somatic embryogenesis and genetic engineering approaches applied to haploids and double-haploid plants produced in short-times by in vitro microspore embryogenesis have a high potential
Characterization of early developmental stages of embryogenesis of both microspore and zygotic embryo origins in Quercus suber Two different embryogenic in vitro systems have been compared in cork oak, embryogenesis of microspores and immature zygotic embryos, to analyze the presence and distribution patterns of various cellular components at early embryogenesis stages and to identify common markers present in the two embryogenic pathways at the initial stages
Summary
In Quercus suber, cork oak, a Mediterranean forest tree of economic and social interest, rapid production of isogenic lines and clonal propagation of elite genotypes have been achieved by developing in vitro embryogenesis from microspores and zygotic embryos respectively. Tree breeding strategies have focused on ways to reduce cycle time and improve the efficiency of selection; here, propagation of selected trees by somatic embryogenesis and genetic engineering approaches applied to haploids and double-haploid plants produced in short-times by in vitro microspore embryogenesis have a high potential. Due to their recalcitrance, the efficiency of embryogenesis in vitro systems in many woody species is still very low. Despite the work performed in the last decades, factors responsible for embryogenesis initiation and embryo development in established cultures are still largely unknown
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