Jackson S L, Hardham A R
Plant Cell Biology Group, Research School of Biological Sciences, The Australian National University, Canberra, Australia.
Eur J Cell Biol. 1996 Feb;69(2):180-8.
We studied the role of cytoplasmic free Ca2+ concentration ([Ca2+]i) in cytokinesis of zoosporangia of the water mold Phytophthora cinnamomi. In these cells cytokinesis is separated from nuclear division and can be triggered at precisely determined times by cold shock. Changes in [Ca2+]i were monitored by ratiometric fluorescence imaging of pressure microinjected Fura-2 dextran. Two increases in [Ca2+]i always occurred in sporangia that underwent cytokinesis in response to cold shock. Within the first minute of cold shock, [Ca2+]i rose rapidly and transiently to levels 25 to 131% higher than the resting level of 104 +/- 54 nM. By 10 min, [Ca2+]i had decreased and was near the initial resting level. The second increase in [Ca2+]i was gradual and prolonged, accompanying cell division. Near completion of cytokinesis, [Ca2+]i had risen to 231 +/- 165 nM. The initial brief rise in [Ca2+]i was absent in sporangia that did not undergo cleavage. Microinjection of the Ca2+ buffer 5,5'-dibromo-BAPTA before cold shock, blocked cytokinesis suggesting that the transient rise in [Ca2+]i may be necessary for induction. The subsequent gradual increase in [Ca2+]i may not be critical because microinjection of 5,5'-dibromo-BAPTA during cleavage plane development did not always perturb division.
我们研究了细胞质游离钙离子浓度（[Ca2+]i）在樟疫霉游动孢子囊胞质分裂中的作用。在这些细胞中，胞质分裂与核分裂分开，并且可以在精确确定的时间通过冷休克触发。通过压力显微注射Fura-2葡聚糖的比率荧光成像监测[Ca2+]i的变化。在因冷休克而进行胞质分裂的孢子囊中，[Ca2+]i总是出现两次升高。在冷休克的第一分钟内，[Ca2+]i迅速短暂升高至比104±54 nM的静息水平高25%至131%的水平。到10分钟时，[Ca2+]i下降并接近初始静息水平。[Ca2+]i的第二次升高是渐进的且持续时间长，伴随着细胞分裂。在胞质分裂接近完成时，[Ca2+]i已升至231±165 nM。未进行分裂的孢子囊中没有出现[Ca2+]i最初的短暂升高。在冷休克前显微注射Ca2+缓冲剂5,5'-二溴-BAPTA可阻断胞质分裂，这表明[Ca2+]i的短暂升高可能是诱导所必需的。随后[Ca2+]i的逐渐升高可能并不关键，因为在分裂平面形成过程中显微注射5,5'-二溴-BAPTA并不总是干扰分裂。
