The role of viruses in the life and death of phytoplankton

虽然浮游植物是水生生态系统的支柱，但它们的生与死策略尚不清楚。由于自然界中存在如此高的丰度，单细胞浮游植物曾经被认为是不朽的，经历永久的无性分裂，只有在被摄入或沉入海洋深处时才会死亡。我们现在开始意识到这些单细胞生物也可能通过许多其他自然方式死亡。然而，浮游植物这些其他死亡模式的过程和重要性仍然知之甚少。尽管尚未分离和表征的藻类病毒相对较少，但现在人们认识到它们在浮游植物的死亡率中发挥着重要作用。在我的实验室中，我们有 3 种不相关的藻类病毒，它们仅得到部分特征。为了进一步了解藻类病毒的多样性，我们的目标是：对 HaNIV 基因组进行测序和注释，检查疾病的传播并表征 Ha2DNAV 感染过程中产生的 2 种病毒粒子，以及表征感染普罗瓦索利赤球菌的病毒。这些新型病毒将与已知的藻类病毒进行比较，以确定相关性并更好地了解病毒多样性。在该研究计划的另一个项目中，我们将研究细胞死亡，细胞死亡可以通过两种机制发生：程序性细胞死亡（PCD）或坏死。这些死亡模式具有非常不同的特征，我们已经开发出在不同种类的藻类中检查这种死亡模式的方法。感染同一宿主（Heterosigma akashiwo）的 3 种不相关病毒（HaNIV、HaV 和 HaRNAV）以及感染 2 种不相关宿主（H. akashiwo 和 Micromonas pusilla）的 2 种相关病毒（HaV 和 MpV）的分离，为我们提供了比较死亡过程的独特机会。我们的目标是确定由病毒和/或宿主决定的死亡特征，作为检查和确定浮游植物群落细胞死亡流行率的重要一步。通过在病毒感染期间抑制 PCD 途径，我们还将确定 PCD 是否是有效病毒感染所必需的，以及它是否作为宿主保护机制被引发。

While phytoplankton are the backbone to aquatic ecosystems, their life and death strategies are not well understood. With such high abundances persisting in nature, single-celled phytoplankton were once believed to be immortal, undergoing perpetual asexual division and only succumbing to death when ingested or sunk to the depths of the ocean. We are now beginning to realize that these single-celled organisms may also die by a number of other natural means. However, the processes and importance of these other modes of death among phytoplankton remain poorly understood. Although relatively few algal viruses have yet been isolated and characterized, they are now recognized to play an important role in the mortality of phytoplankton. In my lab, we have 3 unrelated algal viruses that are only partially characterized. To further understand the diversity of algal viruses our objectives are to: sequence and annotate the genome of HaNIV, examine the transmission of disease and characterize the 2 virions produced during Ha2DNAV infection, and characterize the virus infecting Pycnococcus provasolii. The novel viruses will be compared with known algal viruses to determine relatedness and better understand viral diversity. In another project of this research program we will study cellular death, which can occur by two mechanisms: programmed cell death (PCD) or necrosis. These modes of death have very different signatures, and we have developed methods for examining this in diverse species of algae. The isolation of 3 unrelated viruses (HaNIV, HaV & HaRNAV) that infect the same host (Heterosigma akashiwo), as well as 2 related viruses (HaV & MpV) that infect 2 unrelated hosts (H. akashiwo & Micromonas pusilla), provides us with a unique opportunity to compare the process of death. Our objectives are to determine the characteristics of death that are dictated by the virus and/or the host as an important step toward examining for and determining the prevalence of cell death in phytoplankton communities. By inhibiting the PCD pathway during viral infection, we will also determine if PCD is necessary for a productive viral infection and if it is elicited as a host protection mechanism.