Dinoflagellate Molecular Biology and Mecanisms of Circadian Rhythms

甲藻是海洋生态系统的重要组成部分：它们是全球初级生产(光合碳固定)的主要贡献者，是活珊瑚内的共生体，有些形成有害(产生毒素)的藻华(HAB)。我们对这类生物知之甚少，更不知道它们将如何应对气候变化。此外，甲藻是研究昼夜节律生物化学的有用系统，因为它们的大部分行为和生理在每日周期中变化。我们的主要研究目标是详细阐述生物钟用来控制节奏的机制，这最终可能有助于理解更复杂的人类生物钟系统。作为第二个目标，我们想要更笼统地了解甲藻是如何调节基因表达的。昼夜节律让细胞在一天中的不同时间专门负责不同的功能。在我们目前的模型中，细胞通过改变关键速率限制步骤(RLS)酶的数量、活性或亚细胞位置来实现这一点。因此，我们首先寻找为观察到的节律提供分子解释的生化相关因素。例如，夜间生物发光节律由两个RLS蛋白的量调节，即酶荧光素酶和底物(荧光素)结合蛋白LBP。这两种蛋白质的合成都是通过翻译来调节的，这表明时钟控制的RNA结合蛋白发挥了作用。相比之下，光合作用的每日节律涉及将叶绿体内的Rubisco(碳固定的第一种酶)从产生O2的位置移走。我们现在正在研究碳酸酐酶将二氧化碳输送到Rubisco的能力。最后，我们对细胞分裂的节律感兴趣，它涉及一种被称为门控的现象，即细胞分裂发生在一天中适当的时间和细胞周期阶段的交汇处。在这里，我们的目标是细胞周期蛋白依赖性激酶(CDK)，作为来自两个通路的信号的潜在整合因子。对细胞分裂的控制是理解赤潮的关键。

Dinoflagellates are an important part of the oceans ecosystem: they are major contributors to global primary production (photosynthetic carbon fixation) and are the symbionts inside living coral, and some form harmful (toxin-producing) algal blooms (HAB). We know very little about this class of organisms and even less about how they will cope with climate change. In addition, dinoflagellates are a useful system in which to study the biochemistry of circadian (daily) rhythms since most of their behavior and physiology varies over the daily cycle. Our MAIN RESEARCH GOAL is to elaborate a catalog of mechanisms used by circadian clocks to control rhythms, which may eventually help in understanding the more complex human circadian systems. As a SECONDARY GOAL, we want to understand in more general terms how gene expression is regulated in the dinoflagellates.Circadian rhythms let cells specialize for different functions at different times of day. In our current model, cells achieve this by altering the amount, the activity, or the subcellular location of key rate limiting step (RLS) enzymes. We thus first look for biochemical correlates that provide molecular explanations for the observed rhythms. By way of example, the nightly bioluminescence rhythm is regulated by the amount of two RLS proteins, the enzyme luciferase and the substrate (luciferin) binding protein LBP. The synthesis of both proteins is regulated translationally, suggesting a role for clock-controlled RNA binding proteins. In contrast, the daily rhythm of photosynthesis involves moving Rubisco (the first enzyme in carbon fixation) within the chloroplasts away from the site of O2 production. We are now pursuing carbonic anhydrase enzymes for their ability to deliver CO2 to Rubisco. Lastly, we are interested in the rhythm of cell division, which involves a phenomenon called gating where cell division occurs at the conjunction of an appropriate time of day and cell cycle phase. Here we target cyclin-dependent kinases (CDK) as potential integrators of signals from both pathways. Control of cell division is key to an understanding of HAB.