Department of Botany, University of Texas, 78713, Austin, TX, USA.
Planta. 1989 Jan;177(1):47-57. doi: 10.1007/BF00392153.
The subcellular distribution of actin was investigated in two related species of coenocytic green algae, with immunofluorescence microscopy. Either no, or fine punctate fluorescence was detected in intact cells of Ernodesmis verticillata (Kützing) Børgesen and Boergesenia forbesii (Harvey) Feldmann. A reticulate pattern of fluorescence appears throughout the cortical cytoplasm of Ernodesmis cells shortly after wounding; this silhouettes chloroplasts and small vacuoles. Slender, longitudinal bundles of actin become evident in contracting regions of the cell, superimposed over the reticulum. Thicker portions of the bundles were observed in well-contracted regions, and the highly-convoluted appearance of nearby cortical microtubules indicates contraction of the bundles in these thicker areas. Bundles are no longer evident after healing; only the reticulum remains. In Boergesenia, a wider-mesh reticulum of actin develops in the cortex of wounded cells, which widens further as contractions continue. Cells wounded in Ca(2+)-free medium do not contract, and although the actin reticulum is apparent, no actin bundles were ever observed in these cells. Exogenously applied cytochalasins have no effect on contractions of cut cells or extruded cytoplasm, and normal actin-bundle formation occurs in treated cells. In contrast, erythro-9-[3-(2-hydroxynonyl)]adenine (EHNA) completely inhibits longitudinal contractions in wounded cells, and few uniformly slender actin bundles develop in inhibited cells. These results indicate that wounding stimulates a Ca(2+)-dependent, hierarchical assembly of actin into bundles, whose assembly and functioning are inhibited by EHNA. Contraction of the bundles and concomitant wound healing are followed by cessation of motility and disassembly of the bundles. The spatial and temporal association of the bundles with regions of cytoplasmic contraction, indicates that the actin bundles are directly involved in wound-induced cytoplasmic motility in these algae.
使用免疫荧光显微镜研究了两种相关的共生绿藻中的肌动蛋白的亚细胞分布。在完整的 Ernodesmis verticillata (Kützing) Børgesen 和 Boergesenia forbesii (Harvey) Feldmann 细胞中，要么检测不到，要么检测到精细的点状荧光。在 Ernodesmis 细胞受到创伤后不久，整个皮质细胞质中都会出现网状荧光；这种荧光勾勒出叶绿体和小液泡的轮廓。在细胞的收缩区域，细长的肌动蛋白束变得明显，叠加在网状物上。在收缩区域，可以看到较厚的束的较厚部分，并且附近皮质微管的高度卷曲外观表明这些较厚区域中的束收缩。在愈合后，束不再明显；只剩下网状物。在 Boergesenia 中，受伤细胞的皮质中会形成更宽网眼的肌动蛋白网状物，随着收缩的继续，网状物会进一步变宽。在无钙介质中受伤的细胞不会收缩，尽管可以明显看到肌动蛋白网状物，但在这些细胞中从未观察到肌动蛋白束。细胞松弛素的外源性应用对切割细胞或挤出细胞质的收缩没有影响，并且在处理过的细胞中会正常形成肌动蛋白束。相比之下，erythro-9-[3-(2-hydroxynonyl)]adenine (EHNA) 完全抑制受伤细胞的纵向收缩，并且在抑制的细胞中很少形成均匀细长的肌动蛋白束。这些结果表明，创伤刺激肌动蛋白依赖 Ca2+的、分级组装成束，EHNA 抑制束的组装和功能。束的收缩和伴随的伤口愈合后，运动性停止，束解体。束与细胞质收缩区域的空间和时间关联表明，这些藻类中的肌动蛋白束直接参与了诱导性细胞质运动。
