Collaborative Research: A Matter of Life or Death? Assessing the physiological roles of PCD-related genes to stress adaptation in diatoms

合作研究：生死攸关？

• 批准号: 0927829
• 负责人: Kay Bidle
• 金额: $ 70.79万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0927829&HistoricalAwards=false
• 关键词: Collaborative; Research; Matter; Life; Death

Diatoms are a class of unicellular phytoplankton that account for ~40% of total marine primary productivity in the modern ocean. Since downward fluxes of biogenic silica and organic matter in the modern ocean derive largely from diatom productivity, there is increased interest in the mechanistic processes that regulate their fate. Indeed, the physiological state and life history of diatom assemblages dictate whether diatom Si and its associated organic C are either recycled in the euphotic zone, or exported to depth, placing mechanistic importance on cellular processes mediating bloom to post-bloom transition in response to nutrient stress. Programmed cell death (PCD) triggered by specific environmental stresses (e.g., Fe starvation, viral infection, high light, oxidative stress, and UV exposure) has now been documented in a variety of prokaryotic and eukaryotic unicellular phytoplankton, including diatoms. It provides a mechanistic framework to help explain lysis rates independent of grazing. The expression and activation of metacaspases, putative death proteases, in stressed diatoms, suggest PCD is an integral pathway in these organisms. Currently, the ecological role(s) of PCD-related genes in unicellular phytoplankton and the evolutionary drivers selecting for their retention remain unknown. Their preservation would seem to provide a negative selection pressure, yet their retention and maintenance suggests some sort of ancient, selective advantage. Metacaspases (and other PCD-related genes) may have co-evolved with other metabolic pathways whereby retention and low-level expression served housekeeping or regulatory functions. Elucidation of the ecological role(s) of PCD-related genes, like metacaspases, in diatom field populations requires an understanding of cellular function(s) and induction under relevant stressors. The premise of this proposal is that a subset of putative, PCD-related genes plays heretofore-unappreciated roles in stress adaptation in marine diatoms. The PIs will investigate whether Fe and N availability differentially regulate their expression and activity in T. pseudonana and in coastal diatoms from the California coast. The researchers will elucidate whether distinct PCD-related genes confer increased fitness under Fe or under N-limitation. This research follows from the investigators previous results that a subset of PCD-related genes is differentially expressed in T. pseudonana cells in response to Fe stress. Specific hypotheses are: (1) Expression and activity of PCD-related genes are controlled by Fe or N availability; (2) Overexpression of putative PCD-related genes confers increased fitness under nutrient limitation; (3) Diverse T. psuedonana metacaspases share functional epitope similarities; and (4) PCD-related genes in coastal diatoms display differential responses to steady-state Fe and N limitation. This work integrates physiology, biochemistry, genetics, ultra-trace metal clean techniques and field-based sampling in order to elucidate the ecological function of metacaspases in diatoms and to identify their roles and regulation in natural diatom populations under Fe versus N limitation. This novel interdisciplinary approach is particularly suited to address the roles of these fascinating enzymes.This project will allow for continued professional development of two young PIs and provide an opportunity for a female, postdoctoral associate to get first time PI experience. The proposed project provides a forum for researchers with different educational backgrounds (undergraduate students, graduate students, technician, post-docs, and faculty) to interact and develop. This project provides excellent hands-on training for development of both graduate and undergraduate students and will strongly broaden the participation of women. Proposed research will also foster new national collaborations. Research activities will interface with the Mid-Atlantic Center for Ocean Science Education Excellence (MA-COSEE) and ongoing outreach programs that introduce urban, largely minority, children and families to marine science. The PIs will participate in an ongoing public lecture series at New Jersey's Liberty Science Center entitled "Pulse of the Planet" combined with 2-hour professional development workshop for K-12 teachers. Specific goals are to stimulate awareness of the immense diversity and large-scale importance of marine microbes to ocean function.

硅藻是一类单细胞浮游植物，占现代海洋初级生产力的40%左右。由于现代海洋中生物硅和有机物的向下通量主要来自硅藻的生产力，因此人们对调节其命运的机械过程越来越感兴趣。事实上，硅藻组合的生理状态和生活史决定了硅藻硅及其相关的有机碳是否在真光层中回收，或出口到深处，将机械的重要性细胞过程介导的开花后开花过渡响应营养胁迫。程序性细胞死亡（PCD）由特定的环境应激（例如，铁饥饿，病毒感染，强光，氧化应激和紫外线暴露），现在已经记录在各种原核和真核单细胞浮游植物，包括硅藻。它提供了一个机制框架，以帮助解释裂解率独立放牧。后半胱氨酸蛋白酶，推定的死亡蛋白酶，在强调硅藻的表达和激活，表明PCD是在这些生物体中的一个不可或缺的途径。目前，PCD相关基因在单细胞浮游植物中的生态作用及其保留的进化驱动因素仍然未知。它们的保存似乎提供了一种消极的选择压力，然而它们的保留和维护表明了某种古老的选择优势。后半胱氨酸天冬氨酸蛋白酶（和其他PCD相关基因）可能与其他代谢途径共同进化，从而保留和低水平表达服务管家或调节功能。阐明PCD相关基因的生态作用（S），如metacaspases，在硅藻领域的人口需要了解细胞功能（S）和相关压力下的诱导。这一建议的前提是，一个子集的推定，PCD相关基因发挥迄今为止未被赞赏的作用，在海洋硅藻的压力适应。PI将研究Fe和N的可用性是否差异调节它们在T中的表达和活性。以及来自加州海岸的沿海硅藻。研究人员将阐明不同的PCD相关基因是否在Fe或N限制下赋予增加的适应性。这项研究是根据研究人员先前的结果，PCD相关基因的子集在T。铁胁迫下的Escherichia coli。具体假设如下：（1）PCD相关基因的表达和活性受铁或氮的有效性控制;（2）PCD相关基因的过量表达可提高营养限制下的适合度;（3）不同的T. psuedonana metacaspes具有相似的功能表位;（4）沿海硅藻中PCD相关基因对稳态Fe和N限制表现出不同的反应。本研究综合了生理学、生物化学、遗传学、超痕量金属净化技术和野外采样技术，旨在阐明硅藻中metacaspase的生态学功能，并确定其在Fe和N限制下的自然硅藻种群中的作用和调控。这种新颖的跨学科方法特别适合于解决这些迷人的酶的作用。该项目将允许两个年轻的PI的持续专业发展，并为一名女性博士后助理提供首次获得PI经验的机会。该项目为不同教育背景的研究人员（本科生，研究生，技术人员，博士后和教师）提供了一个互动和发展的论坛。该项目为研究生和本科生的发展提供了极好的实践培训，并将大大扩大妇女的参与。拟议的研究还将促进新的国家合作。研究活动将与中大西洋海洋科学教育卓越中心（MA-COSEE）和正在进行的推广计划对接，这些计划将城市，主要是少数民族，儿童和家庭引入海洋科学。PI将参加在新泽西的自由科学中心正在进行的公开讲座系列题为“地球的脉搏”结合2小时的专业发展讲习班的K-12教师。具体目标是促使人们认识到海洋微生物的巨大多样性和对海洋功能的重要性。