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Immunogold localization of CRT (b, d, f, h, i, m) and distribution of exchangeable Ca²⁺ (c, e, g, j-m) in Petunia micropylar pole of the ovule. a Methylene blue stained longitudinal section of the embryo sac micropylar pole before pollination. b, c, f, g, j, k Distributions of CRT and loosely-bound Ca²⁺ in the micropylar pole of the ovule form unpollinated pistil. d, e, h, i, l, m Distributions of CRT and loosely–bound Ca²⁺ in the micropylar pole of the ovule form pollinated pistil. n Negative immunocytochemical control. o Proteinase K control. p Potassium antimonate precipitation control. c cytoplasm, ccw callosic cell wall, cc central cell, cw cell wall, d dictyosome, ec egg cell, er endoplasmic reticulum, fa filiform apparatus, fcw fibrillar cell wal, m mitochondria, n nucleus, nc nucellus, pt pollen tube, sy synergid, va vacuole. Bars 25 μm (a), 1 μm (j, k, m, p), 500 nm (c, e, f–i, l), 250 nm (b, d, n, o)

Immunogold localization of CRT (b, d, f, h, i, m) and distribution of exchangeable Ca²⁺ (c, e, g, j-m) in Petunia micropylar pole of the ovule. a Methylene blue stained longitudinal section of the embryo sac micropylar pole before pollination. b, c, f, g, j, k Distributions of CRT and loosely-bound Ca²⁺ in the micropylar pole of the ovule form unpollinated pistil. d, e, h, i, l, m Distributions of CRT and loosely–bound Ca²⁺ in the micropylar pole of the ovule form pollinated pistil. n Negative immunocytochemical control. o Proteinase K control. p Potassium antimonate precipitation control. c cytoplasm, ccw callosic cell wall, cc central cell, cw cell wall, d dictyosome, ec egg cell, er endoplasmic reticulum, fa filiform apparatus, fcw fibrillar cell wal, m mitochondria, n nucleus, nc nucellus, pt pollen tube, sy synergid, va vacuole. Bars 25 μm (a), 1 μm (j, k, m, p), 500 nm (c, e, f–i, l), 250 nm (b, d, n, o)

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Calcium (Ca(2+)) plays essential roles in generative reproduction of angiosperms, but the sites and mechanisms of Ca(2+) storage and mobilization during pollen-pistil interactions have not been fully defined. Both external and internal Ca(2+) stores are likely important during male gametophyte communication with the sporophytic and gametophytic cel...

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... Previous work from our laboratory provided evidence that CRT may be involved in Ca 2+ homeostasis and molecular chaperoning during the key reproductive events in Petunia pistil, such as pistil transmitting tract maturation, pollen-pistil interactions, double fertilization, and early embryogenesis [17,18,22]. We also demonstrated that CRT has a critical role in pollen tube growth in vitro [20]. ...
... However, localization of this protein outside the ER has also been observed in eukaryotic cells. Plant CRT was detected in many different compartments and structures, including dictyosomes, vesicles, protein bodies, nucleus, plasma membrane, and the cell wall [22]. Although, some previous work from our lab and others indicated location of CRT in several extracellular regions were somewhat controversial, an elegant work of Luczak et al. [34] provided clear evidence that CRT, similar to several other proteins, is present in the cell walls of few plant species including maize, Lupinus and Arabidopsis. ...
... Although, some previous work from our lab and others indicated location of CRT in several extracellular regions were somewhat controversial, an elegant work of Luczak et al. [34] provided clear evidence that CRT, similar to several other proteins, is present in the cell walls of few plant species including maize, Lupinus and Arabidopsis. We have previously demonstrated that both CRT and exchangeable Ca 2+ were localized to the extracellular peripheries of highly specialized plant cells, such as pollen tubes and synergids [14,16,18,22]. In pollen tubes, CRT labeling was detected in the peripheral ER-rich cytoplasm of the tube adjacent to the cell membrane and in the callosic cell wall. ...
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