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: 0927733
• 负责人: Adam Kustka
• 金额: $ 6.86万
• 依托单位: Rutgers University Newark
• 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 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0927733&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，占现代海洋总初级生产力的40%左右。由于现代海洋中生物成因二氧化硅和有机物的向下流动主要来自硅藻的生产力，因此人们对调节其命运的机制过程的兴趣日益增加。事实上，硅藻组合的生理状态和生活史决定了硅藻Si及其相关有机C是否在光区被循环利用，或被出口到深海，这在响应营养胁迫的细胞过程中发挥了重要的机制作用。程序性细胞死亡（PCD）是由特定的环境应激（如缺铁、病毒感染、强光、氧化应激和紫外线暴露）引发的，现已在包括硅藻在内的多种原核和真核单细胞浮游植物中得到证实。它提供了一个机制框架来帮助解释不受放牧影响的裂解速率。胁迫硅藻中metacaspase（假定的死亡蛋白酶）的表达和激活表明PCD是这些生物体的一个完整途径。目前，pcd相关基因在单细胞浮游植物中的生态作用以及选择其保留的进化驱动因素尚不清楚。它们的保存似乎提供了一种消极的选择压力，但它们的保留和维护表明了某种古老的选择优势。metacaspase（和其他与pcd相关的基因）可能与其他代谢途径共同进化，其中保留和低水平表达具有管家或调节功能。阐明pcd相关基因（如metacaspase）在硅藻野外种群中的生态作用需要了解细胞功能和相关应激源下的诱导。这一建议的前提是假定的一个子集，与pcd相关的基因在海洋硅藻的压力适应中起着迄今未被认识的作用。pi将研究铁和氮的有效性是否在假单胞菌和加利福尼亚海岸硅藻中调节其表达和活性的差异。研究人员将阐明不同的pcd相关基因是否在铁或氮限制下增加适应性。这项研究遵循了研究者先前的结果，即pcd相关基因的一个子集在假单胞菌细胞中对铁胁迫的差异表达。具体假设为：(1)pcd相关基因的表达和活性受铁或氮有效性控制；(2)在营养限制下，过度表达pcd相关基因增加了适应性；(3)不同的T. psuedonana metacaspase具有功能表位相似性；(4)沿海硅藻中pcd相关基因对稳态Fe和N限制表现出不同的响应。本研究综合运用生理学、生物化学、遗传学、超痕量金属清洁技术和野外采样等方法，阐明硅藻中metacaspase的生态功能，并在铁氮限制下确定其在天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令人着迷的酶的作用。该项目将为两名年轻的PI提供持续的专业发展，并为一名女性博士后提供首次获得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优秀的实践培训，并将有力地扩大妇女的参与。拟议的研究也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）和正在进行的向城市，主要是少数民族，儿童和家庭介绍海洋科学的外展项目相结合。这些pi将参加正在新泽西州自由科学中心举行的题为“地球脉动”的系列公开讲座，并结合为K-12教师举办的2小时专业发展研讨会。具体目标是激发人们对海洋微生物的巨大多样性和对海洋功能的大规模重要性的认识。