title: Moderate stress responses and specific changes in polyamine metabolism characterize Scots pine somatic embryogenesis.
abstract: Somatic embryogenesis (SE) is one of the methods with the highest potential for the vegetative propagation of commercially important coniferous species. However, many conifers, including Scots pine (Pinus sylvestris L.), are recalcitrant to SE and a better understanding of the mechanisms behind the SE process is needed. In Scots pine SE cultures, embryo production is commonly induced by the removal of auxin, addition of abscisic acid (ABA) and the desiccation of cell masses by polyethylene glycol (PEG). In the present study, we focus on the possible link between the induction of somatic embryo formation and cellular stress responses such as hydrogen peroxide protection, DNA repair, changes in polyamine (PA) metabolism and autophagy. Cellular PA contents and the expression of the PA metabolism genes arginine decarboxylase (ADC), spermidine synthase (SPDS), thermospermine synthase (ACL5) and diamine oxidase (DAO) were analyzed, as well as the expression of catalase (CAT), DNA repair genes (RAD51, KU80) and autophagy-related genes (ATG5, ATG8) throughout the induction of somatic embryo formation in Scots pine SE cultures. Among the embryo-producing SE lines, the expression of ADC, SPDS, ACL5, DAO, CAT, RAD51, KU80 and ATG8 showed consistent profiles. Furthermore, the overall low expression of the stress-related genes suggests that cells in those SE lines were not stressed but recognized the ABA+PEG treatment as a signal to trigger the embryogenic pathway. In those SE lines that were unable to produce embryos, cells seemed to experience the ABA+PEG treatment mostly as osmotic stress and activated a wide range of stress defense mechanisms. Altogether, our results suggest that the direction to the embryogenic pathway is connected with cellular stress responses in Scots pine SE cultures. Thus, the manipulation of stress response pathways may provide a way to enhance somatic embryo production in recalcitrant Scots pine SE lines.
authors.affiliation: Genetics and Physiology Department, University of Oulu, PO Box 3000, FI-90014 Oulu, Finland heigggi@gmail.com.
authors.forename: Heikki M
authors.initials: HM
authors.lastname: Salo
authors.affiliation: Natural Resources Institute Finland (Luke), Parkano Unit, FI-39700 Parkano, Finland.
authors.forename: Tytti
authors.initials: T
authors.lastname: Sarjala
authors.affiliation: Genetics and Physiology Department, University of Oulu, PO Box 3000, FI-90014 Oulu, Finland.
authors.forename: Anne
authors.initials: A
authors.lastname: Jokela
authors.affiliation: Genetics and Physiology Department, University of Oulu, PO Box 3000, FI-90014 Oulu, Finland.
authors.forename: Hely
authors.initials: H
authors.lastname: Häggman
authors.affiliation: Genetics and Physiology Department, University of Oulu, PO Box 3000, FI-90014 Oulu, Finland Natural Resources Institute Finland (Luke), Rovaniemi Unit, FI-96300 Rovaniemi, Finland.
authors.forename: Jaana
authors.initials: J
authors.lastname: Vuosku
mesh_terms: D001343:Autophagy / Q000235:genetics; D004260:DNA Repair / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D041605:Pinus sylvestris / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D011073:Polyamines / Q000378:metabolism*; D012995:Solubility; D013312:Stress, Physiological / Q000235:genetics
chemical_list: D011073:Polyamines; D006861:Hydrogen Peroxide
keywords: DNA repair; Pinus; ROS protection; autophagy; catalase; drought stress; polyethylene glycol