Comprehensive Analyses of Antifreeze Capacities in Arctic and Northern Cods at the Protein and Encoded Levels, and the Molecular of the Cod Antifreeze Glycoprotein Gene

北极和北方鳕鱼抗冻能力的蛋白质和编码水平以及鳕鱼抗冻糖蛋白基因分子的综合分析

• 批准号: 0002654
• 负责人: Chi-Hing Cheng
• 金额: $ 44.26万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-09-01 至 2003-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0002654&HistoricalAwards=false
• 关键词: Comprehensive; Analyses; Antifreeze; Capacities; Arctic

The twenty-four or so cod species of the Arctic and northern cool-temperate oceans belonging to the family Gadidae include many of the most commercially important cod fishes. Five of these species are known to have an antifreeze glycoprotein (AFGP) that is important for their survival in their various cold-water habitats. Most of the cod AFGP studies were conducted during 1975-1985, and provided basic information on the protein structure and seasonal changes in AFGP levels in some of the five known AFGP-bearing cods. None of the other cods that may encounter freezing conditions have been examined for possible presence of an antifreeze function, and no information at all on the cod AFGP function at the molecular level was available until 1997 when the first AFGP gene sequence and structure from the Arctic cod Boreogadus saida were reported with a high AFGP coding capacity in this most-northerly species. Thus the AFGP systems of the different cod species are far from being thoroughly understood. This project proposes to conduct comprehensive characterizations and analyses of the AFGP system of the different gadids using contemporary techniques. The overall goal is to assess their respective freeze-avoidance capacities at both the protein (AFGP protein structures and production) and molecular (AFGP genes and gene families and their transcription) levels, and how these relate to the differential physiological demands imposed by their diverse habitats which span a range of latitudes and environmental severity. The AFGP systems of the cods will be contrasted among the cod species, and with the constitutive high capacities in their south-polar counterparts, the Antarctic notothenioids, which are unrelated perciform fishes that make a near-identical AFGP to survive in the world's most thermally stable and coldest marine waters at the opposite pole. A key question in the field of antifreeze research is where these novel antifreeze proteins came from. The PIs have previously determined the evolutionary origin and molecular mechanism that produced the Antarctic notothenioid AFGP gene which played a crucial role in the survival and organismal success of these fishes in the frigid Antarctic waters. Through molecular analyses, the second major goal of the project is to decipher the origin and evolutionary history of the cod AFGP gene, that had led to the remarkable 'bipolar' evolutionary convergence of similar AFGPs in two unrelated fish groups.Ten different marine gadid species, one of which includes two genetically distinct populations, will be examined. Specific areas of studies include: (1) comparative analyses of blood AFGP levels, protein structure and heterogeneity between and within cod species from different latitudes and habitats to determine the influence of environmental severity on antifreeze production; (2) determination of the circannual AFGP production cycles (AFGP protein levels and transcription of mRNA) of three high-latitude cods and their relationship to the temporal variations in environmental conditions specific to each of their habitats; (3) determination of the encoded capacity for AFGP production in different cods by analyzing the complexity of their AFGP gene sequences, structures, the organization of these genes in the genome, and the size of the gene family; (4) characterization of the distribution of AFGP expression in different tissues and non-vascular fluid compartments to determine all possible lines of defense against freezing in the cods; (5) determination whether hitherto unexamined gadids (6 different northerly distributed species) have an antifreeze protein through detection for both blood antifreeze activity and presence of AFGP-like sequences in their genome; and (6) deciphering the origin and the evolutionary process of cod AFGP gene.

大约有24种鳕鱼生活在北极和北部寒温带海洋，属于鳕鱼科，其中包括许多最具商业价值的鳕鱼。其中五种已知具有防冻糖蛋白（AFGP），这对它们在各种冷水栖息地的生存至关重要。大多数鳕鱼AFGP研究是在1975-1985年间进行的，提供了5种已知的含AFGP鳕鱼的蛋白质结构和AFGP水平的季节变化的基本信息。直到1997年，北极鳕鱼（Boreogadus saida）的第一个AFGP基因序列和结构被报道在这个最北端的物种中具有很高的AFGP编码能力，才有了关于鳕鱼AFGP功能在分子水平上的信息。因此，不同种类鳕鱼的AFGP系统还远远没有被完全了解。本项目拟采用现代技术对不同基因的AFGP系统进行综合表征和分析。总体目标是评估它们各自在蛋白质（AFGP蛋白结构和生产）和分子（AFGP基因和基因家族及其转录）水平上的抗冻能力，以及这些能力与它们跨越一系列纬度和环境严重性的不同栖息地所施加的差异生理需求之间的关系。鳕科鱼的AFGP系统将鳕鱼物种之间的对比,和本构高能力在南极的同行,南极notothenioids perciform无关的鱼类,使类同AFGP生存在世界上最耐热和寒冷的海洋水域相对立。这些新型抗冻蛋白的来源是目前抗冻研究领域的一个关键问题。π之前已经确定产生的进化起源和分子机制,南极notothenioid AFGP基因起到了至关重要的作用在这些鱼类的生存和有机体的成功在寒冷的南极海域。通过分子分析，该项目的第二个主要目标是破译鳕鱼AFGP基因的起源和进化历史，该基因导致了两个不相关鱼类群体中相似AFGP的显著“双极性”进化趋同。十种不同的海洋生物，其中一种包括两个基因不同的种群，将被研究。具体研究领域包括：(1)比较分析血液中AFGP水平、蛋白质结构和来自不同纬度和栖息地的鳕鱼物种之间和内部的异质性，以确定环境严重程度对防冻剂生产的影响；(2)测定了3种高纬度鱼类AFGP的年周期（AFGP蛋白水平和mRNA转录）及其与不同生境环境条件变化的关系；(3)通过分析不同鱼类AFGP基因序列的复杂性、结构、基因在基因组中的组织和基因家族的大小，确定不同鱼类生产AFGP的编码能力；(4)表征AFGP在不同组织和非血管液体室中的表达分布，以确定在cods中抵御冷冻的所有可能防线；(5)通过检测血液抗冻活性和基因组中afgp样序列的存在，确定迄今为止未检测的gadids（6种不同的北方分布物种）是否含有抗冻蛋白；(6)破译鳕鱼AFGP基因的起源和进化过程。