Functional adaptation of diatoms to environmental conditions in sea ice of the Southern Ocean

硅藻对南大洋海冰环境条件的功能适应

• 批准号: NE/I001751/1
• 负责人: Thomas Mock
• 金额: $ 4.9万
• 依托单位: University of East Anglia
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI001751%2F1
• 关键词: Functional; adaptation; diatoms; environmental; conditions

In winter sea ice covers an area of up to 7% of the earth surface, which clearly as such is one of the largest biomes on earth. Sea ice can be thought of as a thin blanket covering the ocean surface, which controls, but is also controlled by fluxes of heat and moisture. The life cycles of many marine organisms ranging from bacteria, algae, small animals, whales and even humans are influenced by large-scale cycles of sea ice formation. Thus, sea ice is recognized as a fundamental component of the system earth, which is key for our predictions of future climate conditions as has become increasingly apparent in the last decade due to rapid global warming. The possible implications of a gradual loss of sea ice due to higher global temperatures are not fully understood yet but pictures of shrinking Arctic sea ice in summer has become the focus of media and increasing attention from the general public. Focus of this grant application are microalgae that live inside the porous matrix of sea ice. Most of them belong to the group of diatoms, which in general play a key role on earth because they are responsible for 25% of primary fixation of carbon dioxide, which is as much as all tropical rain forests combined. Why especially diatoms dominate sea ice algal communities is not fully understood yet but we know that they are virtually the sole source of fixed carbon for higher trophical levels in ice-covered waters. In fact, the short food chain diatom-krill-whale is depend on ice algae because they provide food for young krill when other sources of food in winter are lacking. This food chain might be severely influenced by a reduction of sea ice due to global warming. Despite the significance of polar sea ice algae virtually nothing is know about their fundamental biology. This is why the US Department of Energy (DOE) has selected one of the most important sea ice diatom species (Fragilariopsis cylindrus) to sequence its genome under the guidance of the applicant. The genome sequence is now available and has brought exciting new insights into life at and below the freezing point of sea water. For instance, the genome encodes a previously unknown family of antifreeze proteins. It also encodes genes that were not anticipated to be present in this genome such as a gene that encodes a protein from bacteria for harvesting light to generate ATP. It was not anticipated because F. cylindrus has chloroplasts in which photosynthesis like in higher plants generates ATP. Thus, the function of this gene is not known yet as for many other genes in the genome as well. One first step to shed light on the function of genes is to study their expression under different environmental conditions, which is one main goal of this proposal. We propose to conduct experiments where we treat the cells under conditions that are present in sea ice (e.g. freezing temperatures, nutrient limitation) and which are predicted outcomes of global warming in polar regions (e.g. elevated temperatures and carbon dioxide concentrations). We will then sequence the transcriptome with high-throughput sequencing technology to identify genes that are differentially expressed under our experimental conditions. Selected genes will be confirmed by quantitative qPCR. This study will help to identify the short term acclimation of F. cylindrus to sea ice as it forms every autumn. Adaptation to sea ice will be studied by comparative genome analysis between F. cylindrus and the close relative F. kerguelensis, which lives also in cold polar sea water but doesn't thrive in sea ice. This comparison will not only shed light on specific adaptation necessary for thriving in sea ice but also the predicted outcomes of global warming in polar oceans because ice free waters will more and more dominate these habitats. High-throughput sequencing will be used to sequence the genome of F. kerguelensis and large and small scale genome analysis will reveal the differences.

冬季海冰覆盖的面积高达地球表面的 7%，这显然是地球上最大的生物群落之一。海冰可以被认为是覆盖海洋表面的一层薄薄的毯子，它控制着热量和水分的流动，但也受到热量和水分流动的控制。许多海洋生物的生命周期，包括细菌、藻类、小动物、鲸鱼甚至人类，都受到大规模海冰形成周期的影响。因此，海冰被认为是地球系统的基本组成部分，这对于我们预测未来气候条件至关重要，由于全球快速变暖，这一点在过去十年中变得越来越明显。全球气温升高导致海冰逐渐消失可能产生的影响尚不完全清楚，但夏季北极海冰缩小的照片已成为媒体的焦点，也越来越受到公众的关注。该拨款申请的重点是生活在海冰多孔基质内的微藻。它们中的大多数属于硅藻类，硅藻通常在地球上发挥着关键作用，因为它们负责二氧化碳初级固定的 25%，这相当于所有热带雨林的总和。为什么硅藻在海冰藻类群落中占主导地位尚不完全清楚，但我们知道它们实际上是冰覆盖水域中较高营养水平的固定碳的唯一来源。事实上，硅藻-磷虾-鲸的短食物链依赖于冰藻，因为当冬季缺乏其他食物来源时，它们为幼年磷虾提供食物。全球变暖导致的海冰减少可能会严重影响这条食物链。尽管极地海冰藻类具有重要意义，但实际上人们对它们的基本生物学一无所知。这就是为什么美国能源部（DOE）选择了最重要的海冰硅藻物种之一（圆柱脆弱脆片）在申请人的指导下对其基因组进行测序。基因组序列现已可用，并为海水冰点及以下的生命带来了令人兴奋的新见解。例如，基因组编码了一个以前未知的抗冻蛋白家族。它还编码了预计不会出现在该基因组中的基因，例如编码来自细菌的蛋白质的基因，该蛋白质用于收集光以产生 ATP。这是没有预料到的，因为 F. cylindrus 具有叶绿体，叶绿体中像高等植物一样进行光合作用，产生 ATP。因此，该基因的功能尚不清楚，基因组中的许多其他基因也是如此。阐明基因功能的第一步是研究它们在不同环境条件下的表达，这是该提案的一个主要目标。我们建议进行实验，在海冰中存在的条件（例如冰冻温度、营养限制）以及极地地区全球变暖的预测结果（例如气温升高和二氧化碳浓度升高）下处理细胞。然后，我们将利用高通量测序技术对转录组进行测序，以鉴定在我们的实验条件下差异表达的基因。选定的基因将通过定量 qPCR 进行确认。这项研究将有助于确定 F. cylindrus 对每年秋天海冰形成的短期适应情况。将通过比较 F. cylindrus 和近亲 F. kerguelensis 之间的基因组分析来研究对海冰的适应，F. kerguelensis 也生活在寒冷的极地海水中，但在海冰中无法繁衍生息。这种比较不仅将揭示海冰繁荣所需的特定适应，而且还将揭示极地海洋全球变暖的预测结果，因为无冰水域将越来越多地主宰这些栖息地。高通量测序将用于对 F. kerguelensis 的基因组进行测序，大型和小型基因组分析将揭示差异。

项目成果

Global discovery and characterization of small non-coding RNAs in marine microalgae.

海洋微藻中小非编码 RNA 的全球发现和表征。

• DOI: 10.1186/1471-2164-15-697
• 发表时间: 2014-08-20
• 期刊: BMC genomics
• 影响因子: 4.4
• 作者: Lopez-Gomollon S;Beckers M;Rathjen T;Moxon S;Maumus F;Mohorianu I;Moulton V;Dalmay T;Mock T
• 通讯作者: Mock T

Evolutionary genomics of the cold-adapted diatom Fragilariopsis cylindrus

• DOI: 10.1038/nature20803
• 发表时间: 2017-01-26
• 期刊: NATURE
• 影响因子: 64.8
• 作者: Mock, Thomas;Otillar, Robert P.;Grigoriev, Igor V.
• 通讯作者: Grigoriev, Igor V.

Polar Microalgae: New Approaches towards Understanding Adaptations to an Extreme and Changing Environment.

• DOI: 10.3390/biology3010056
• 发表时间: 2014-01-28
• 期刊: Biology
• 影响因子: 4.2
• 作者: Lyon BR;Mock T
• 通讯作者: Mock T

The Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP): illuminating the functional diversity of eukaryotic life in the oceans through transcriptome sequencing.

• DOI: 10.1371/journal.pbio.1001889
• 发表时间: 2014-06
• 期刊: PLoS biology
• 影响因子: 9.8
• 作者: Keeling PJ;Burki F;Wilcox HM;Allam B;Allen EE;Amaral-Zettler LA;Armbrust EV;Archibald JM;Bharti AK;Bell CJ;Beszteri B;Bidle KD;Cameron CT;Campbell L;Caron DA;Cattolico RA;Collier JL;Coyne K;Davy SK;Deschamps P;Dyhrman ST;Edvardsen B;Gates RD;Gobler CJ;Greenwood SJ;Guida SM;Jacobi JL;Jakobsen KS;James ER;Jenkins B;John U;Johnson MD;Juhl AR;Kamp A;Katz LA;Kiene R;Kudryavtsev A;Leander BS;Lin S;Lovejoy C;Lynn D;Marchetti A;McManus G;Nedelcu AM;Menden-Deuer S;Miceli C;Mock T;Montresor M;Moran MA;Murray S;Nadathur G;Nagai S;Ngam PB;Palenik B;Pawlowski J;Petroni G;Piganeau G;Posewitz MC;Rengefors K;Romano G;Rumpho ME;Rynearson T;Schilling KB;Schroeder DC;Simpson AG;Slamovits CH;Smith DR;Smith GJ;Smith SR;Sosik HM;Stief P;Theriot E;Twary SN;Umale PE;Vaulot D;Wawrik B;Wheeler GL;Wilson WH;Xu Y;Zingone A;Worden AZ
• 通讯作者: Worden AZ