title: Expression of catalase and retinoblastoma-related protein genes associates with cell death processes in Scots pine zygotic embryogenesis.
abstract: BACKGROUND
  The cell cycle and cellular oxidative stress responses are tightly controlled for proper growth and development of Scots pine (Pinus sylvestris L.) seed. Programmed cell death (PCD) is an integral part of the embryogenesis during which megagametophyte cells in the embryo surrounding region (ESR) and cells in the nucellar layers face death. In the present study, we show both the tissue and developmental stage specific expression of the genes encoding the autophagy related ATG5, catalase (CAT), and retinoblastoma related protein (RBR) as well as the connection between the gene expressions and cell death programs.
  
  
  RESULTS
  We found strong CAT expression in the cells of the developing embryo throughout the embryogenesis as well as in the cells of the megagametophyte and the nucellar layers at the early embryogeny. The CAT expression was found to overlap with both the ATG5 expression and hydrogen peroxide localization. At the late embryogeny, CAT expression diminished in the dying cells of the nucellar layers as well as in megagametophyte cells, showing the first signs of incipient cell death. Accumulation of starch and minor RBR expression were characteristic of megagametophyte cells in the ESR, whereas strong RBR expression was found in the cells of the nucellar layers at the late embryogeny.
  
  
  CONCLUSIONS
  Our results suggest that ATG5, CAT, and RBR are involved in the Scots pine embryogenesis and cell death processes. CAT seems to protect cells against hydrogen peroxide accumulation and oxidative stress related cell death especially during active metabolism. The opposite expression of RBR in the ESR and nucellar layers alongside morphological characteristics emphasizes the different type of the cell death processes in these tissues. Furthermore, the changes in ATG5 and RBR expressions specifically in the megagametophyte cells dying by necrotic cell death suggest the genetic regulation of developmental necrosis in Scots pine embryogenesis.
authors.affiliation: Genetics and Physiology Unit, University of Oulu, P.O. Box 3000, FI-90014, Oulu, Finland. jaana.vuosku@luke.fi.|Current address: Natural Resources Institute Finland (Luke), Rovaniemi Unit, FI-96301, Rovaniemi, Finland. jaana.vuosku@luke.fi.
authors.forename: Jaana
authors.initials: J
authors.lastname: Vuosku
authors.affiliation: Genetics and Physiology Unit, University of Oulu, P.O. Box 3000, FI-90014, Oulu, Finland. suvi.sutela@oulu.fi.
authors.forename: Suvi
authors.initials: S
authors.lastname: Sutela
authors.affiliation: Genetics and Physiology Unit, University of Oulu, P.O. Box 3000, FI-90014, Oulu, Finland. kestila.johanna@gmail.com.
authors.forename: Johanna
authors.initials: J
authors.lastname: Kestilä
authors.affiliation: Genetics and Physiology Unit, University of Oulu, P.O. Box 3000, FI-90014, Oulu, Finland. anne.jokela@oulu.fi.
authors.forename: Anne
authors.initials: A
authors.lastname: Jokela
authors.affiliation: Natural Resources Institute Finland (Luke), Parkano Unit, Kaironiementie 15, FI-39700, Parkano, Finland. tytti.sarjala@luke.fi.
authors.forename: Tytti
authors.initials: T
authors.lastname: Sarjala
authors.affiliation: Genetics and Physiology Unit, University of Oulu, P.O. Box 3000, FI-90014, Oulu, Finland. hely.haggman@oulu.fi.
authors.forename: Hely
authors.initials: H
authors.lastname: Häggman
mesh_terms: D002374:Catalase / Q000235:genetics* / Q000378:metabolism; D016923:Cell Death; D018506:Gene Expression Regulation, Plant; D041605:Pinus sylvestris / Q000196:embryology / Q000201:enzymology* / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics* / Q000378:metabolism; D012639:Seeds / Q000201:enzymology / Q000235:genetics
chemical_list: D010940:Plant Proteins; D016160:Retinoblastoma Protein; D002374:Catalase