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One tissue, two fates: different roles of megagametophyte cells during Scots pine embryogenesis.

Vuosku J, Sarjala T, Jokela A, Sutela S, Sääskilahti M, Suorsa M, Läärä E, Häggman H - J. Exp. Bot. (2009)

Bottom Line: In the Scots pine (Pinus sylvestris L.) seed, embryos grow and develop within the corrosion cavity of the megagametophyte, a maternally derived haploid tissue, which houses the majority of the storage reserves of the seed.It was found that the megagametophyte was viable from the early phases of embryo development until the early germination of mature seeds.Their cell wall, plasma membrane, and nuclear envelope broke down with the release of cell debris and nucleic acids into the corrosion cavity.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Oulu, PO Box 3000, 90014 Oulu, Finland. jaana.vuosku@oulu.fi

ABSTRACT
In the Scots pine (Pinus sylvestris L.) seed, embryos grow and develop within the corrosion cavity of the megagametophyte, a maternally derived haploid tissue, which houses the majority of the storage reserves of the seed. In the present study, histochemical methods and quantification of the expression levels of the programmed cell death (PCD) and DNA repair processes related genes (MCA, TAT-D, RAD51, KU80, and LIG) were used to investigate the physiological events occurring in the megagametophyte tissue during embryo development. It was found that the megagametophyte was viable from the early phases of embryo development until the early germination of mature seeds. However, the megagametophyte cells in the narrow embryo surrounding region (ESR) were destroyed by cell death with morphologically necrotic features. Their cell wall, plasma membrane, and nuclear envelope broke down with the release of cell debris and nucleic acids into the corrosion cavity. The occurrence of necrotic-like cell death in gymnosperm embryogenesis provides a favourable model for the study of developmental cell death with necrotic-like morphology and suggests that the mechanism underlying necrotic cell death is evolutionary conserved.

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Related in: MedlinePlus

Acridine orange stained Scots pine embryos and megagametophyte tissue during embryogenesis. The double-stranded nucleic acids (i.e. DNA) fluoresce green and the single-stranded (i.e. RNA) fluoresce red. (A) Dominant and subordinate early embryos in the corrosion cavity on sampling date I. (B) Dominant early embryo in the corrosion cavity on sampling date II. (C) Dominant late embryo in the corrosion cavity on sampling date III. (D) Dominant late embryo and the dying subordinate embryos in the corrosion cavity on sampling date III. (E) Late embryo filling the corrosion cavity on sampling date IV. (F) Dying cells of subordinate embryos broke down, resulting in a leakage of nucleic acids into the surrounding extracellular space. (G) During embryo development, the cell wall, plasma membrane, and nuclear envelope of the megagametophyte cells lining the corrosion cavity broke down with the release of cell debris and nucleic acids into the corrosion cavity (early embryogeny, sampling date II). (H) During early embryogeny, nuclei in megagametophyte cells stained green, except for rRNA containing nucleoli, which were red. In the cytoplasmic region, the red colour indicated the presence of mRNA and active gene expression. (I) During late embryogeny, nuclei in megagametophyte cells appeared normal with the presence of nucleoli and with no sign of DNA fragmentation. (J) Control sample with no acridine orange staining. Bars: (G, H, I) 10 μm, (F) 20 μm, (A, C, J) 50 μm, and (B, D, E) 100 μm.
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fig1: Acridine orange stained Scots pine embryos and megagametophyte tissue during embryogenesis. The double-stranded nucleic acids (i.e. DNA) fluoresce green and the single-stranded (i.e. RNA) fluoresce red. (A) Dominant and subordinate early embryos in the corrosion cavity on sampling date I. (B) Dominant early embryo in the corrosion cavity on sampling date II. (C) Dominant late embryo in the corrosion cavity on sampling date III. (D) Dominant late embryo and the dying subordinate embryos in the corrosion cavity on sampling date III. (E) Late embryo filling the corrosion cavity on sampling date IV. (F) Dying cells of subordinate embryos broke down, resulting in a leakage of nucleic acids into the surrounding extracellular space. (G) During embryo development, the cell wall, plasma membrane, and nuclear envelope of the megagametophyte cells lining the corrosion cavity broke down with the release of cell debris and nucleic acids into the corrosion cavity (early embryogeny, sampling date II). (H) During early embryogeny, nuclei in megagametophyte cells stained green, except for rRNA containing nucleoli, which were red. In the cytoplasmic region, the red colour indicated the presence of mRNA and active gene expression. (I) During late embryogeny, nuclei in megagametophyte cells appeared normal with the presence of nucleoli and with no sign of DNA fragmentation. (J) Control sample with no acridine orange staining. Bars: (G, H, I) 10 μm, (F) 20 μm, (A, C, J) 50 μm, and (B, D, E) 100 μm.

Mentions: In the present study, acridine orange, a dual fluorescence dye, was applied in order to detect nucleic acids in the embryo and megagametophyte cells during Scots pine embryogenesis. The embryos were at the early embryogeny stage (Fig. 1A, B) before the appearance of the root meristem. During late embryogeny, the dominant embryo was maturating (Fig. 1C), whereas the growth of the subordinate embryos was retarded, and they fell more and more behind the leading embryo (Fig. 1D). Finally, the subordinate embryos disappeared and the leading embryo occupied the corrosion cavity (Fig. 1E). In the dying subordinate embryos, the cells broke down, resulting in a leakage of nucleic acids into the surrounding extracellular space (Fig. 1F).


One tissue, two fates: different roles of megagametophyte cells during Scots pine embryogenesis.

Vuosku J, Sarjala T, Jokela A, Sutela S, Sääskilahti M, Suorsa M, Läärä E, Häggman H - J. Exp. Bot. (2009)

Acridine orange stained Scots pine embryos and megagametophyte tissue during embryogenesis. The double-stranded nucleic acids (i.e. DNA) fluoresce green and the single-stranded (i.e. RNA) fluoresce red. (A) Dominant and subordinate early embryos in the corrosion cavity on sampling date I. (B) Dominant early embryo in the corrosion cavity on sampling date II. (C) Dominant late embryo in the corrosion cavity on sampling date III. (D) Dominant late embryo and the dying subordinate embryos in the corrosion cavity on sampling date III. (E) Late embryo filling the corrosion cavity on sampling date IV. (F) Dying cells of subordinate embryos broke down, resulting in a leakage of nucleic acids into the surrounding extracellular space. (G) During embryo development, the cell wall, plasma membrane, and nuclear envelope of the megagametophyte cells lining the corrosion cavity broke down with the release of cell debris and nucleic acids into the corrosion cavity (early embryogeny, sampling date II). (H) During early embryogeny, nuclei in megagametophyte cells stained green, except for rRNA containing nucleoli, which were red. In the cytoplasmic region, the red colour indicated the presence of mRNA and active gene expression. (I) During late embryogeny, nuclei in megagametophyte cells appeared normal with the presence of nucleoli and with no sign of DNA fragmentation. (J) Control sample with no acridine orange staining. Bars: (G, H, I) 10 μm, (F) 20 μm, (A, C, J) 50 μm, and (B, D, E) 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2657542&req=5

fig1: Acridine orange stained Scots pine embryos and megagametophyte tissue during embryogenesis. The double-stranded nucleic acids (i.e. DNA) fluoresce green and the single-stranded (i.e. RNA) fluoresce red. (A) Dominant and subordinate early embryos in the corrosion cavity on sampling date I. (B) Dominant early embryo in the corrosion cavity on sampling date II. (C) Dominant late embryo in the corrosion cavity on sampling date III. (D) Dominant late embryo and the dying subordinate embryos in the corrosion cavity on sampling date III. (E) Late embryo filling the corrosion cavity on sampling date IV. (F) Dying cells of subordinate embryos broke down, resulting in a leakage of nucleic acids into the surrounding extracellular space. (G) During embryo development, the cell wall, plasma membrane, and nuclear envelope of the megagametophyte cells lining the corrosion cavity broke down with the release of cell debris and nucleic acids into the corrosion cavity (early embryogeny, sampling date II). (H) During early embryogeny, nuclei in megagametophyte cells stained green, except for rRNA containing nucleoli, which were red. In the cytoplasmic region, the red colour indicated the presence of mRNA and active gene expression. (I) During late embryogeny, nuclei in megagametophyte cells appeared normal with the presence of nucleoli and with no sign of DNA fragmentation. (J) Control sample with no acridine orange staining. Bars: (G, H, I) 10 μm, (F) 20 μm, (A, C, J) 50 μm, and (B, D, E) 100 μm.
Mentions: In the present study, acridine orange, a dual fluorescence dye, was applied in order to detect nucleic acids in the embryo and megagametophyte cells during Scots pine embryogenesis. The embryos were at the early embryogeny stage (Fig. 1A, B) before the appearance of the root meristem. During late embryogeny, the dominant embryo was maturating (Fig. 1C), whereas the growth of the subordinate embryos was retarded, and they fell more and more behind the leading embryo (Fig. 1D). Finally, the subordinate embryos disappeared and the leading embryo occupied the corrosion cavity (Fig. 1E). In the dying subordinate embryos, the cells broke down, resulting in a leakage of nucleic acids into the surrounding extracellular space (Fig. 1F).

Bottom Line: In the Scots pine (Pinus sylvestris L.) seed, embryos grow and develop within the corrosion cavity of the megagametophyte, a maternally derived haploid tissue, which houses the majority of the storage reserves of the seed.It was found that the megagametophyte was viable from the early phases of embryo development until the early germination of mature seeds.Their cell wall, plasma membrane, and nuclear envelope broke down with the release of cell debris and nucleic acids into the corrosion cavity.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Oulu, PO Box 3000, 90014 Oulu, Finland. jaana.vuosku@oulu.fi

ABSTRACT
In the Scots pine (Pinus sylvestris L.) seed, embryos grow and develop within the corrosion cavity of the megagametophyte, a maternally derived haploid tissue, which houses the majority of the storage reserves of the seed. In the present study, histochemical methods and quantification of the expression levels of the programmed cell death (PCD) and DNA repair processes related genes (MCA, TAT-D, RAD51, KU80, and LIG) were used to investigate the physiological events occurring in the megagametophyte tissue during embryo development. It was found that the megagametophyte was viable from the early phases of embryo development until the early germination of mature seeds. However, the megagametophyte cells in the narrow embryo surrounding region (ESR) were destroyed by cell death with morphologically necrotic features. Their cell wall, plasma membrane, and nuclear envelope broke down with the release of cell debris and nucleic acids into the corrosion cavity. The occurrence of necrotic-like cell death in gymnosperm embryogenesis provides a favourable model for the study of developmental cell death with necrotic-like morphology and suggests that the mechanism underlying necrotic cell death is evolutionary conserved.

Show MeSH
Related in: MedlinePlus