Cubitt A B, Firtel R A, Fischer G, Jaffe L F, Miller A L
Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA.
Development. 1995 Aug;121(8):2291-301. doi: 10.1242/dev.121.8.2291.
To examine the patterns of high free cytosolic calcium or [Ca2+]i during Dictyostelium's development, we expressed apoaequorin in D. discoideum, reconstituted aequorin and observed the resultant patterns of calcium-dependent luminescence. Specific, high calcium zones are seen throughout normal multicellular development and are roughly coincident with those regions that later differentiate into stalk or stalk-like cells. A slug, for example, shows a primary high calcium zone within its front quarter and a secondary one around its tail; while a mound shows such a zone around the periphery of its base. Combined with previous evidence, our findings support the hypothesis that high [Ca2+]i feeds back to favor the stalk pathway. We also discovered several high calcium zones within the mound's base that do not coincide with any known prepatterns in D. discoideum. These include two, relatively persistent, antipodal strips along the mound's periphery. These various persistent zones of high calcium are largely made up of frequent, 10 to 30 second long, semiperiodic calcium spikes. Each of these spikes generates a correspondingly short-lived, 200 to 500 microns long, high calcium band which extends along the nearby surface. Similar, but relatively large and infrequent, spikes generate cross bands which extend across migrating slugs and just behind their advancing tips as well as across the peripheries of rotating mounds and midway between their antipodal strips. Moreover, calcium has a doubling time of about a second as various spikes rise. This last observation suggests that the calcium bands seen in Dictyostelium may be generated by so-called fast calcium waves.
为了研究盘基网柄菌发育过程中游离胞质钙或[Ca2+]i升高的模式，我们在盘基网柄菌中表达脱辅基水母发光蛋白，重组水母发光蛋白并观察由此产生的钙依赖性发光模式。在整个正常多细胞发育过程中都能看到特定的高钙区域，这些区域大致与后来分化为柄或柄状细胞的区域重合。例如，蛞蝓在其前四分之一处显示一个主要的高钙区域，在其尾部周围显示一个次要的高钙区域；而丘状体在其基部周边显示这样一个区域。结合先前的证据，我们的发现支持这样的假设，即高[Ca2+]i反馈有利于柄细胞分化途径。我们还在丘状体基部发现了几个高钙区域，这些区域与盘基网柄菌中任何已知的预模式都不重合。其中包括沿着丘状体周边的两条相对持久的对映带。这些各种持续的高钙区域主要由频繁出现的、持续10到30秒的半周期性钙尖峰组成。这些尖峰中的每一个都会产生一个相应的短暂的、长200到500微米的高钙带，该高钙带沿着附近的表面延伸。类似但相对较大且不频繁的尖峰会产生交叉带，这些交叉带穿过迁移的蛞蝓并在其前进尖端后方，以及穿过旋转丘状体的周边和其对映带之间的中间位置。此外，随着各种尖峰的上升，钙的加倍时间约为一秒。最后的这一观察结果表明，在盘基网柄菌中看到的钙带可能是由所谓的快速钙波产生的。
