Photoacclimation during senescence and the control of longevity in microalgae

衰老是所有生命的基本组成部分，但对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的强烈兴趣，但包括细菌在内的单细胞生物衰老的认识令许多人感到惊讶。更令人惊讶的是，我们可以在实验室中减缓许多生物的衰老，使它们具有更长的寿命。一种简单但有效的方法是减少他们饮食中的卡路里含量，这种方法称为卡路里限制。我们建议研究衰老或“条件性衰老”的过程中的一个模型，微藻系统-莱茵衣藻。随着细胞生长，它们达到最大细胞密度，因为营养素耗尽，并进入有限生长期，随后不可避免地进入死亡阶段。我们正在研究细胞在衰老过程中保护自己免受过多光线的方式。我们的目标是确定负责吸收光的蛋白质如何改变其组织，从有效的光吸收转换为能量耗散，从而保护细胞免受损害并延长寿命。我们还建议研究文化中的微藻寿命的决定因素和参与控制响应的细胞途径。我们将研究基因的表达，以确定基因网络，这些基因网络可能为细胞如何应对衰老的挑战以及改变介质的卡路里含量如何影响这些条件下的生存提供线索。我们还建议研究遗传相同细胞的微藻种群中个体之间的生化和生理差异，以研究在压力条件下长期生存的其他策略。最终，用于在稳定期存活、控制细胞密度和延长寿命的策略的知识将在需要大规模生产藻类的微藻生物燃料和生物产品行业中有用。对细胞生长和存活的限制的理解将最终影响生物质的产生和产量的增加。

Aging is a fundamental part of all life, yet there remains considerable debate as to the causes and mechanisms of why organisms age and the 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. Even more surprising, we can slow down ageing in many organisms in the lab such that they have a longer lifespan. A simple but robust way of doing this by reducing the calorie content of their diet, an approach called caloric restriction. 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 followed inevitably by a death phase. We are proposing to examine the way in which cells protect themselves from too much light as they age. Our goal is to determine how the proteins responsible for absorbing light change their organization to toggle from efficient light absorption to energy dissipation as heat, thereby protecting the cell from damage and extending longevity. We also propose to study the determinants of microalgal longevity in culture and the cellular pathways involved in controlling the response. We will examine the expression of genes to identify gene networks that may provide clues as to how cells meet the challenges of senescence and how altering caloric content of the media may affect survival under these conditions. We also propose to examine the biochemical and physiological differences between individuals in a microalgal population of genetically identical cells to examine additional strategies for long-term survival under stressful conditions. Ultimately, the knowledge on the strategies used to survive stationary phase, control cell density and extend longevity will be useful in the 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.