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Distribution of lipid transfer protein 1 (LTP1) epitopes associated with morphogenic events during somatic embryogenesis of Arabidopsis thaliana.

Potocka I, Baldwin TC, Kurczynska EU - Plant Cell Rep. (2012)

Bottom Line: The labelling was strongest in both the outer periclinal and anticlinal walls of the adaxial, protodermal cells of the proximal region of the cotyledon.The putative role(s) of lipid transfer proteins in the formation of lipid lamellae and in cell differentiation are discussed.Key message Occurrence of lipid transfer protein 1 epitopes in Arabidopsis explant cells accompanies changes in cell fate and may be correlated with the deposition of lipid substances in the cell walls.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Cell Biology, University of Silesia, Jagiellońska 28, 40-032, Katowice, Poland. izabela.potocka@us.edu.pl

ABSTRACT
Using immunocytochemical methods, at both the light and electron microscopic level, we have investigated the spatial and temporal distribution of lipid transfer protein 1 (LTP1) epitopes during the induction of somatic embryogenesis in explants of Arabidopsis thaliana. Immunofluorescence labelling demonstrated the presence of high levels of LTP1 epitopes within the proximal regions of the cotyledons (embryogenic regions) associated with particular morphogenetic events, including intense cell division activity, cotyledon swelling, cell loosening and callus formation. Precise analysis of the signal localization in protodermal and subprotodermal cells indicated that cells exhibiting features typical of embryogenic cells were strongly labelled, both in walls and the cytoplasm, while in the majority of meristematic-like cells no signal was observed. Staining with lipophilic dyes revealed a correlation between the distribution of LTP1 epitopes and lipid substances within the cell wall. Differences in label abundance and distribution between embryogenic and non-embryogenic regions of explants were studied in detail with the use of immunogold electron microscopy. The labelling was strongest in both the outer periclinal and anticlinal walls of the adaxial, protodermal cells of the proximal region of the cotyledon. The putative role(s) of lipid transfer proteins in the formation of lipid lamellae and in cell differentiation are discussed. Key message Occurrence of lipid transfer protein 1 epitopes in Arabidopsis explant cells accompanies changes in cell fate and may be correlated with the deposition of lipid substances in the cell walls.

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Immunofluorescence localization of LTP1 epitopes in loosened tissues of embryogenic regions. a, c Loosened protoderm of the cotyledons, labelling present on the surface of the cells (solid arrowheads) and in the intercellular spaces (empty arrowheads), day 6 (a) and day 7 (c) of culture. b, d Phase contrast views of sections shown in a, c respectively, clearly visible cell pattern. e Deposition of LTP1 epitopes (asterisks) in the spaces between loosened ground tissue cells of the cotyledon, day 11 of culture. f The section shown in e with nuclei stained with DAPI (blue), asterisks point to intercellular spaces. g Negative control for e, no labelling. Pr protoderm. Scale bars 10 μm (a–g)
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Fig2: Immunofluorescence localization of LTP1 epitopes in loosened tissues of embryogenic regions. a, c Loosened protoderm of the cotyledons, labelling present on the surface of the cells (solid arrowheads) and in the intercellular spaces (empty arrowheads), day 6 (a) and day 7 (c) of culture. b, d Phase contrast views of sections shown in a, c respectively, clearly visible cell pattern. e Deposition of LTP1 epitopes (asterisks) in the spaces between loosened ground tissue cells of the cotyledon, day 11 of culture. f The section shown in e with nuclei stained with DAPI (blue), asterisks point to intercellular spaces. g Negative control for e, no labelling. Pr protoderm. Scale bars 10 μm (a–g)

Mentions: As the explants increased in volume, a specific loosening of the peripheral cell layers was observed (Fig. 2). The continuity of the adaxial protoderm of the swollen embryogenic region was broken (Fig. 2a–d) and in walls of the loosened cells an intense signal (continuous or punctate) was observed to be present (Fig. 2a, c). Signal also occurred outside the cells: either on the surface of the protodermal cells (weaker punctate fluorescence, Fig. 2a, c, solid arrowheads) or in the intercellular spaces between cells (strong solid signal, Fig. 2a, as well as weak punctate signal, Fig. 2c, empty arrowheads). In phase contrast micrographs (Fig. 2b, d) of the sections shown in Fig. 2a, c the spaces between the loosened protodermal cells are clearly visible. In older explants (second and third week of culture), a distinct loosening was also observed in ground tissue layers of the cotyledons (Fig. 2e, f). This was accompanied by the formation of large intercellular spaces in which the signal generated by the anti-AtLTP1 antibody was very intense (Fig. 2e, asterisks). Both DAPI staining (Fig. 2f) and phase contrast microscopy (not shown) revealed the absence of nuclei within the labelled areas, indicating the extracellular deposition of the protein.Fig. 2


Distribution of lipid transfer protein 1 (LTP1) epitopes associated with morphogenic events during somatic embryogenesis of Arabidopsis thaliana.

Potocka I, Baldwin TC, Kurczynska EU - Plant Cell Rep. (2012)

Immunofluorescence localization of LTP1 epitopes in loosened tissues of embryogenic regions. a, c Loosened protoderm of the cotyledons, labelling present on the surface of the cells (solid arrowheads) and in the intercellular spaces (empty arrowheads), day 6 (a) and day 7 (c) of culture. b, d Phase contrast views of sections shown in a, c respectively, clearly visible cell pattern. e Deposition of LTP1 epitopes (asterisks) in the spaces between loosened ground tissue cells of the cotyledon, day 11 of culture. f The section shown in e with nuclei stained with DAPI (blue), asterisks point to intercellular spaces. g Negative control for e, no labelling. Pr protoderm. Scale bars 10 μm (a–g)
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Fig2: Immunofluorescence localization of LTP1 epitopes in loosened tissues of embryogenic regions. a, c Loosened protoderm of the cotyledons, labelling present on the surface of the cells (solid arrowheads) and in the intercellular spaces (empty arrowheads), day 6 (a) and day 7 (c) of culture. b, d Phase contrast views of sections shown in a, c respectively, clearly visible cell pattern. e Deposition of LTP1 epitopes (asterisks) in the spaces between loosened ground tissue cells of the cotyledon, day 11 of culture. f The section shown in e with nuclei stained with DAPI (blue), asterisks point to intercellular spaces. g Negative control for e, no labelling. Pr protoderm. Scale bars 10 μm (a–g)
Mentions: As the explants increased in volume, a specific loosening of the peripheral cell layers was observed (Fig. 2). The continuity of the adaxial protoderm of the swollen embryogenic region was broken (Fig. 2a–d) and in walls of the loosened cells an intense signal (continuous or punctate) was observed to be present (Fig. 2a, c). Signal also occurred outside the cells: either on the surface of the protodermal cells (weaker punctate fluorescence, Fig. 2a, c, solid arrowheads) or in the intercellular spaces between cells (strong solid signal, Fig. 2a, as well as weak punctate signal, Fig. 2c, empty arrowheads). In phase contrast micrographs (Fig. 2b, d) of the sections shown in Fig. 2a, c the spaces between the loosened protodermal cells are clearly visible. In older explants (second and third week of culture), a distinct loosening was also observed in ground tissue layers of the cotyledons (Fig. 2e, f). This was accompanied by the formation of large intercellular spaces in which the signal generated by the anti-AtLTP1 antibody was very intense (Fig. 2e, asterisks). Both DAPI staining (Fig. 2f) and phase contrast microscopy (not shown) revealed the absence of nuclei within the labelled areas, indicating the extracellular deposition of the protein.Fig. 2

Bottom Line: The labelling was strongest in both the outer periclinal and anticlinal walls of the adaxial, protodermal cells of the proximal region of the cotyledon.The putative role(s) of lipid transfer proteins in the formation of lipid lamellae and in cell differentiation are discussed.Key message Occurrence of lipid transfer protein 1 epitopes in Arabidopsis explant cells accompanies changes in cell fate and may be correlated with the deposition of lipid substances in the cell walls.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Cell Biology, University of Silesia, Jagiellońska 28, 40-032, Katowice, Poland. izabela.potocka@us.edu.pl

ABSTRACT
Using immunocytochemical methods, at both the light and electron microscopic level, we have investigated the spatial and temporal distribution of lipid transfer protein 1 (LTP1) epitopes during the induction of somatic embryogenesis in explants of Arabidopsis thaliana. Immunofluorescence labelling demonstrated the presence of high levels of LTP1 epitopes within the proximal regions of the cotyledons (embryogenic regions) associated with particular morphogenetic events, including intense cell division activity, cotyledon swelling, cell loosening and callus formation. Precise analysis of the signal localization in protodermal and subprotodermal cells indicated that cells exhibiting features typical of embryogenic cells were strongly labelled, both in walls and the cytoplasm, while in the majority of meristematic-like cells no signal was observed. Staining with lipophilic dyes revealed a correlation between the distribution of LTP1 epitopes and lipid substances within the cell wall. Differences in label abundance and distribution between embryogenic and non-embryogenic regions of explants were studied in detail with the use of immunogold electron microscopy. The labelling was strongest in both the outer periclinal and anticlinal walls of the adaxial, protodermal cells of the proximal region of the cotyledon. The putative role(s) of lipid transfer proteins in the formation of lipid lamellae and in cell differentiation are discussed. Key message Occurrence of lipid transfer protein 1 epitopes in Arabidopsis explant cells accompanies changes in cell fate and may be correlated with the deposition of lipid substances in the cell walls.

Show MeSH
Related in: MedlinePlus