Oscillator Control of Cell Division Cycles in Euglena

在已提出的其他机制中， 微生物细胞分裂周期（CDC），自主生物 振荡器，范围从那些松弛型到那些 具有极限环动力学，提供了一种可能的方法， 整合细胞周期转运、退出 逮捕 这项研究的长期目标是确定 假定耦合到CDC的振荡器的性质， 以生成分裂的周期性和其他CDC“地标”（如 以及通常作为昼夜节律的基础）。 作为 工作假设，部分基于最近在藻类中的发现， 鞭毛虫，Euglena gracilis，已经提出NAD+， 线粒体钙转运系统，钙-钙调蛋白，NADP+ 磷酸酶和NAD+激酶，也许，cAMP一起可以 构成了一个可持续的昼夜节律 振荡器 这些元件将构成时钟的“齿轮” 潜在的细胞分裂的明显节奏（和其他 变量或“手”）。 的 在本项目早期工作中采用的方法将 持续期间内的 首先，将确定是否每个连续的 所提出的控制回路的元件表现出昼夜节律 在野生型裸藻培养物和 在自由运行条件下保持的无叶绿素突变体 (both在存在和不存在有据可查的节律的情况下， 细胞分裂）。 然后，为了确定是否每个 元素代表时钟的“齿轮”，各种药物的脉冲 而已知会影响这些元素的化学物质 应用。 直接激活和抑制应分别 在生物化学节奏和生物化学反应中产生相移， 分裂节律 特别强调NAD+ 激酶、钙和cAMP--假定的时钟元件， 已经被详细研究过了。 最终，目标将 将描绘振荡器和振荡器之间的耦合链路。 由CDC监管。 这项研究的目的是描绘出生物化学步骤 被认为是昼夜节律振荡器的组成部分， 构成了绿色植物细胞分裂周期的节律， 裸藻

Among other mechanisms that have been proposed to control microbial cell division cycles (CDC), autonomous biological oscillators, ranging from those of the relaxation type to those having limit cycle dynamics, provide a possible means of integrating the disparate concepts of cell cycle transit, exit and arrest. The long-range goal of this research is to determine the nature of the oscillator(s) presumed to couple to the CDC and to generate periodicity of division and other CDC "landmarks" (as well as to underlie circadian rhythmicity in general). As a working hypothesis, based in part on recent findings in the algal flagellate, Euglena gracilis, it has been proposed that NAD+, the mitochondrial calcium transport system, calcium-calmodulin, NADP+ phosphatase and NAD+ kinase, and, perhaps, cAMP together could constitute a light-entrainable, self-sustaining circadian oscillator. These elements would comprise "gears" of the clock underlying the overt rhythm of cell division (and other variables, or "hands") in eukaryotic microorganisms. The approach initiated during earlier work on this project will be continued. First, it will be ascertained whether each successive element of this proposed control loop exhibits circadian rhythmicity in cultures of wild-type Euglena and of an achlorophyllous mutant maintained under free-running conditions (both in the presence and absence of the well documented rhythm of cell division). Then, in order to determine whether each element represents a "gear" of the clock, pulses of various drugs and chemicals which are known to affect these elements will be applied. Direct activation as well as inhibition should each generate phase shifts in the biochemical rhythms and in the division rhythm. Particular emphasis will be given to NAD+ kinase, calcium, and cAMP--putative clock elements that have already been explored in some detail. Ultimately, the goal will be to delineate the coupling links between the oscillator and the CDC regulated by it. The goal of this research is to delineate the biochemical steps proposed to be the components of a circadian oscillator that may underlie the rhythm of the cell division cycle in the green alga, Euglena.