title: Toward establishing a morphological and ultrastructural characterization of proembryogenic masses and early somatic embryos of Araucaria angustifolia (Bert.) O. Kuntze.
abstract: Somatic embryogenesis is a morphogenetic route useful for the study of embryonic development, as well as the large-scale propagation of endangered species, such as the Brazilian pine (Araucaria angustifolia). In the present study, we investigated the morphological and ultrastructural organization of A. angustifolia somatic embryo development by means of optical and electron microscopy. The proembryogenic stage was characterized by the proliferation of proembryogenic masses (PEMs), which are cellular aggregates composed of embryogenic cells (ECs) attached to suspensor-like cells (SCs). PEMs proliferate through three developmental stages, PEM I, II, and III, by changes in the number of ECs and SCs. PEM III-to-early somatic embryo (SE) transition was characterized by compact clusters of ECs growing out of PEM III, albeit still connected to it by SCs. Early SEs showed a dense globular embryonic mass (EM) and suspensor region (SR) connected by embryonic tube cells (TCs). By comparison, early somatic and zygotic embryos showed similar morphology. ECs are round with a large nucleus, nucleoli, and many cytoplasmic organelles. In contrast, TCs and SCs are elongated and vacuolated with cellular dismantling which is associated with programmed cell death of SCs. Abundant starch grains were observed in the TCs and SCs, while proteins were more abundant in the ECs. Based on the results of this study, a fate map of SE development in A. angustifolia is, for the first time, proposed. Additionally, this study shows the cell biology of SE development of this primitive gymnosperm which may be useful in evolutionary studies in this area.
authors.affiliation: Plant Physiology Laboratory, Department of Botany, Federal University of Santa Catarina, Florianópolis, SC, 88040-900, Brazil. neusa.steiner@ufsc.br.
authors.forename: Neusa
authors.identifier: 0000-0001-6063-9242
authors.initials: N
authors.lastname: Steiner
authors.affiliation: Graduate Program in Plant Genetic Resources, Department of Plant Science, Federal University of Santa Catarina, C.P. 476, Florianópolis, SC, 88040-900, Brazil.
authors.forename: Francine L
authors.initials: FL
authors.lastname: Farias-Soares
authors.affiliation: Plant Cell Biology Laboratory, Department of Cell Biology, Embryology and Genetics, Federal University of Santa Catarina, C.P. 476, Florianópolis, SC, 88049-900, Brazil.
authors.forename: Éder C
authors.initials: ÉC
authors.lastname: Schmidt
authors.affiliation: Laboratory of Plant Developmental Physiology and Genetics, Department of Plant Science, Federal University of Santa Catarina, C.P. 476, Florianópolis, SC, 88040-900, Brazil.
authors.forename: Maria L T
authors.initials: ML
authors.lastname: Pereira
authors.affiliation: Laboratory of Plant Developmental Physiology and Genetics, Department of Plant Science, Federal University of Santa Catarina, C.P. 476, Florianópolis, SC, 88040-900, Brazil.
authors.forename: Bruna
authors.initials: B
authors.lastname: Scheid
authors.affiliation: Plant Cell Biology Laboratory, Department of Cell Biology, Embryology and Genetics, Federal University of Santa Catarina, C.P. 476, Florianópolis, SC, 88049-900, Brazil.|Department of Biological Sciences, University of Joinville Region, Joinville, SC, Brazil.
authors.forename: Gladys D
authors.initials: GD
authors.lastname: Rogge-Renner
authors.affiliation: Plant Cell Biology Laboratory, Department of Cell Biology, Embryology and Genetics, Federal University of Santa Catarina, C.P. 476, Florianópolis, SC, 88049-900, Brazil.|Central Laboratory of Electron Microscopy, Federal University of Santa Catarina, Florianópolis, SC, Brazil.
authors.forename: Zenilda L
authors.initials: ZL
authors.lastname: Bouzon
authors.affiliation: Laboratory of Plant Developmental Physiology and Genetics, Department of Plant Science, Federal University of Santa Catarina, C.P. 476, Florianópolis, SC, 88040-900, Brazil.
authors.forename: Daniela
authors.initials: D
authors.lastname: Schmitz
authors.affiliation: Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Guiraldes 2160, Pab. 2, Ciudad Universitaria, C1428EGA, Buenos Aires, Argentina.
authors.forename: Sara
authors.initials: S
authors.lastname: Maldonado
authors.affiliation: Laboratory of Plant Developmental Physiology and Genetics, Department of Plant Science, Federal University of Santa Catarina, C.P. 476, Florianópolis, SC, 88040-900, Brazil.
authors.forename: Miguel P
authors.initials: MP
authors.lastname: Guerra
mesh_terms: D046508:Culture Techniques; D012639:Seeds / Q000254:growth & development / Q000648:ultrastructure*; D014197:Trees / Q000254:growth & development / Q000648:ultrastructure*
keywords: Conifers; Histochemistry; Pluripotency; Somatic embryogenesis; Suspensor cell