Antenna systems, acclimation and the molecular basis of conditional senescence in Chlamydomonas

衰老和衰老是所有生命的基本组成部分，但关于生物体衰老的原因和机制以及控制寿命的条件仍然存在相当大的争论。虽然衰老一直是多细胞生物体的浓厚兴趣，但人们意识到包括细菌在内的单细胞生物体的衰老让许多人感到惊讶。我们建议用微藻系统--莱茵衣藻来研究衰老或“条件性衰老”的过程。随着细胞的生长，当营养物质耗尽时，它们达到最大细胞密度，并进入称为静止期的有限增长期，随后不可避免地进入死亡阶段。我们正在研究与细胞生长有关的两个主要概念。首先，我们正在研究微藻通过测量光合作用的变化来减少静止阶段光诱导的氧化应激的策略。在动物中，氧化应激是导致衰老的主要假说，而藻类在有限生长期间特别容易受到氧化应激的影响。这些分析还将检查衰老的触发因素和影响文化寿命的条件。其次，在分批培养中，细胞达到最大细胞密度，我们将测试是否存在“群体感应”分子，这些分子被释放以控制培养中的个体数量。我们的预测是，这些对细胞密度的控制有助于保存营养物质，以便驯化并延长静止状态下的存活时间。最终，在需要大规模生产藻类的萌芽微藻生物燃料和生物产品工业中，关于用于在静止阶段生存、控制细胞密度和延长寿命的策略的知识将是有用的。对细胞生长和生存极限的理解最终将影响生产生物质和增加产量的方法。

Aging and senescence are a fundamental part of all life, yet there remains considerable debate as to the causes and mechanisms of why organisms age and conditions that control longevity. While aging has been of intense interest in multicellular organisms, the realization that unicellular organisms age, including bacteria, has come to many as a surprise. We are proposing to study the process of aging or "conditional senescence" with a model, microalgal system--Chlamydomonas reinhardtii. As cells grow, they reach a maximum cell density as nutrients become depleted and enter a period of limited growth called stationary phase, followed inevitably by a death phase. There are two primary concepts involved with the growth of cells that we are examining. First, we are investigating the strategies microalgae use to minimize oxidative stress induced by light during stationary phase by measuring changes in photosynthesis. In animals, oxidative stress is a leading hypothesis as a cause of aging and algae would be particularly susceptible to oxidative stress during periods of limited growth. These analyses will also examine senescence triggers and the conditions that affect culture longevity. Second, in batch culture, cells reach a maximum cell density and we will test for the presence of "quorum sensing" molecules that are released to control the number of individuals in culture. Our prediction is that these controls on cell density help to conserve nutrients to allow for acclimation and extend the survival time in stationary. Ultimately, the knowledge on the strategies used to survive stationary phase, control cell density and extend longevity will be useful in the budding microalgal biofuel and bioproduct industry, where large scale production of algae is required. An understanding of the limits to cell growth and survival will ultimately affect approaches for the generation of biomass and increasing yields.