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，但人们对它们的生死策略还没有很好的了解。由于自然界中持续存在如此高的数量，单细胞浮游植物曾被认为是不朽的，经历了永久的无性分裂，只有在被摄取或沉入海洋深处时才会死亡。我们现在开始意识到，这些单细胞有机体也可能通过其他一些自然方式死亡。然而，浮游植物中这些其他死亡方式的过程和重要性仍然知之甚少。虽然目前分离和鉴定的藻类病毒相对较少，但它们在浮游植物死亡中起着重要作用。在我的实验室里，我们有三种不相关的藻类病毒，它们只有部分特征。为了进一步了解藻类病毒的多样性，我们的目标是：对HaNIV的基因组进行测序和注释，检查疾病的传播，鉴定在Ha2DNAV感染过程中产生的两个病毒粒子，并对感染原皮诺球菌的病毒进行特征分析。这些新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。在这个研究计划的另一个项目中，我们将研究细胞死亡，它可以通过两种机制发生：程序性细胞死亡(PCD)或坏死。这些死亡模式有非常不同的特征，我们已经开发出在不同藻类中检测这一点的方法。3种不相关的病毒(HaNIV、HAV和HaRNAV)感染同一宿主(赤潮异弯菌)，以及2种相关的病毒(HAV和MPV)感染2种不相关的宿主(H.akashiwo和Micromonas pusilla)，这为我们提供了一个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中细胞死亡流行率的重要步骤。通过在病毒感染期间抑制PCD途径，我们还将确定PCD是否是有效的病毒感染所必需的，以及它是否被诱导为一种宿主保护机制。

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.