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首页> 外文期刊>Protoplasma: An International Journal of Cell Biology >Ultrastructure of vascular cambial cell cytokinesis in pine seedlings preserved by cryofixation and substitution
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Ultrastructure of vascular cambial cell cytokinesis in pine seedlings preserved by cryofixation and substitution

机译：冷冻固定和替代保存的松树幼苗血管维管细胞胞质的超微结构

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Trees depend on the secondary vascular cambium to produce cells for new xylem and phloem. The fusiform cells of this lateral meristem are long and narrow, presenting special challenges for arranging the mitotic spindle and phragmoplast. Fusiform cambial cells of Pinus ponderosa and Pinus contorta were studied by cryofixation and cryosubstitution which preserved ultrastructure and phases of cytokinesis with a resolution not previously attained. Membranous structures including the plasma membrane, tonoplast, and those of other organelles were smooth and unbroken, indicating that they were preserved while the protoplasm was in a fully turgid state. Mitotic spindles separated daughter chromosomes diagonally across the radial width of the cells. The cell plate was initiated at an angle to the cell axis between the anaphase chromosomes by a microtubule array which organized vesicles at the phragmoplast midline. Within the phragmoplast, vesicles initially joined across thin tubular projections and then amalgamated into a tubulo-vesicular network. Axial expansion of the cell plate generated two opposing phragmoplasts connected by a thin, extended bridge of cell plate and cytoplasm that was oriented along the cell axis. In the cytoplasmic bridge trailing each phragmoplast, the callose-rich tubular network gradually consolidated into a fenestrated plate and then a complete cell wall. Where new membrane merged with old, the parent plasmalemma appeared to be loosened from the cell wall and the membranes joined via a short tubulo-vesicular network. These results have not been previously reported in cambial tissue, but the same phases of cytokinesis have been observed in cryofixed root tips and suspension-cultured cells of tobacco. [References: 44]
机译：树木依靠次生血管形成层产生新的木质部和韧皮部细胞。该侧生分生组织的梭形细胞长而窄，对安排有丝分裂纺锤体和睑板膜提出了特殊的挑战。通过冷冻固定和冷冻替换研究了黄松和扭曲松的梭形冈比亚细胞，该细胞保留了胞质分裂的超微结构和阶段，其分辨率以前未达到。包括质膜，液泡膜和其他细胞器的膜结构是光滑且完整的，表明它们在原生质完全处于饱水状态时得以保留。有丝分裂纺锤体沿细胞的径向宽度沿对角线分隔子染色体。细胞板由微管阵列以与后期染色体之间的细胞轴成一定角度起始，该微管阵列在囊膜中线处组织了囊泡。在睑板膜内，囊泡最初通过薄的管状突起汇合，然后合并为肾小管-囊泡网络。细胞板的轴向扩增产生了两个相对的角膜质，由薄薄的，延伸的细胞板和沿细胞轴定向的细胞质桥连接。在尾随每个膜质体的细胞质桥中，富含call的管状网络逐渐合并为有孔的板，然后形成完整的细胞壁。在新的膜与旧的膜融合的地方，亲本浆膜似乎从细胞壁上松开，并且膜通过短的肾小泡-囊泡网络连接在一起。这些结果以前尚未在冈比亚组织中报道，但是在冷冻固定的根尖和烟草悬浮培养的细胞中观察到了相同的胞质分裂阶段。 [参考：44]

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