Adaptation of the green seaweed Ulva and its microbiome to cold temperature in Antarctica (COLDULVA)

COLDULVA（读作cold-Ulva）项目调查了绿色大型石莼（也称为海莴苣）的冷适应性，这种植物在世界各地的沿海地区都有。石莼的特点是对环境变化的适应性很强。因此，它经常出现在被人类严重污染的沃茨，也出现在南极洲等极端自然条件下。然而，石莼的生长和形态发生依赖于相关细菌释放促进生长的化合物（形态发生素）。在无菌条件下，石莼发育成未分化细胞的愈伤组织。该项目旨在确定在短期寒冷反应和适应过程中受到刺激的应激调节基因和代谢产物，特别考虑到石莼的微生物组。有趣的是，冷适应（即南极/冷温带）石莼物种也在较高的温度下生长。然而，美国的暖温带地区。mutabilis在低温下不生长，相关的基本细菌也不生长。这些观察结果为从内在（藻类代谢）和外在（微生物组）因素的角度解读石莼中的冷响应基因和代谢产物铺平了道路。COLDULVA将比较暖温带模式系统可变石莼（最初收集于葡萄牙的Ria福尔摩沙）与乔治王岛（南极洲）波特湾的南极/寒温带石莼样本菌株。我们假设，如果石莼的微生物组也适应环境变化，以提供必要的藻类生长促进化合物，那么石莼将对压力做出适当的反应。在第一个供资期间，采用了以下三种方法来解决“是否存在适应南极环境条件的关键基因和代谢物”这一关键问题？ 从南极温性石莼中分离到一株能促进温性石莼低温生长的细菌。由于差异基因表达和代谢产物产生的藻类代谢的变化进行了研究后，转移到寒冷的温度，以确定石莼的核心应力响应基因和代谢产物。COLDULVA在其第二个资助期内的目标是：（1）整合我们的分裂样本研究的代谢组和转录组数据，以确定寒冷胁迫条件下的基因和代谢物模式。(2)利用MALDI质谱成像技术研究冷胁迫下石莼-细菌共生过程中的天然产物。(3)使用剂量-反应关系定量形态原菌体蛋白，以阐明其在石莼及其相关细菌之间共生的冷适应中的潜在作用。作为第二个资助期的结果，COLDULVA将提供对细菌大型藻类相互作用的调控网络和细菌介导的石莼冷适应，藻类表面的细菌定居和冷胁迫下的形态发生的见解。

The project COLDULVA (read cold-Ulva) investigates the cold adaptation of the green macroalga Ulva, also known as sea lettuce, which occurs worldwide in coastal areas. Ulva is characterised by excellent adaptability to changes in its environment. It is therefore often found in waters heavily polluted by humans, but also under extreme natural conditions such as in Antarctica. However, Ulva´s growth and morphogenesis depend on the associated bacteria releasing growth-promoting compounds (morphogens). Under bacteria-free conditions, Ulva develops into a callus of non-differentiated cells. The project aimed to identify stress-regulated genes and metabolites that are stimulated during the short-term cold response and acclimation under specific consideration of Ulva´s microbiome.Interestingly, cold-adapted (i.e. the Antarctic/cold temperate) Ulva species also grow at a higher temperature. However, the warm temperate U. mutabilis does not grow at low temperature, and neither do the associated essential bacteria. These observations pave the way to decipher the cold-responsive genes and metabolites in Ulva from the perspective of both intrinsic (algal metabolism) and extrinsic (microbiome) factors. COLDULVA will compare the warm temperate model system Ulva mutabilis (originally collected in the Ria Formosa, Portugal) with sampled Antarctic/cold temperate Ulva strains in the Potter Cove at King George Island (Antarctica). We hypothesise that Ulva will react properly to stress if its microbiome also adapts to environmental changes to provide the necessary algal growth-promoting compounds. In the first funding period, the following three approaches were performed to address the key question “Are there key genes and metabolites for adaptation to Antarctic environmental conditions?” Bacteria were isolated from Antarctic temperate Ulva species to promote the growth of the warm temperate Ulva mutabilis at low temperature. Changes in the algal metabolism due to differential gene expression and metabolite production were investigated upon a shift to cold temperature in order to define the Ulva’s core stress-responsive genes and metabolites. COLDULVA aims during its second funding period: (1) To integrate the metabolome and transcriptome data of our split-sample study for identifying genes and metabolites patterns under cold stress conditions. (2) To decipher the natural products involved in Ulva-bacteria symbiosis under cold stress using MALDI MS imaging for spatial and temporal resolution. (3) To quantify the morphogen thallusin in order to unravel its potential role in cold-adaptation of the symbiosis between Ulva and its associated bacteria using dose-response relationships. As a result of the second funding period, COLDULVA will provide insights onto the regulatory networks of bacterial macroalgal interactions and the bacteria-mediated cold adaptation of Ulva, the bacterial settlement on the algal surface and morphogen production under cold stress.