Cell walls and symbioses of the economically important brown seaweed Ascophyllum nodosum

在过去的30年里，我的研究主要集中在经济上重要的褐藻Ascophyllum nodosum的生物学上。这是一种独特的生物学特性：它的寿命极长（可能长达100年），并且具有使其成为北大西洋冷温带沃茨潮间带基础物种的生态学。Ascophyllum是一个复杂的共生群落的主要宿主，包括两种专性红藻（Vertebrata lanosa，Choreocolax polysiphalus），一种系统专性真菌（Mycophycias ascophylli）和一种兼性附生褐藻（Elachista fucicola）及其相关的海洋昆虫（Halocladius variabilis）。 我的工作在很大程度上涉及发展的共生协会的理解和这个社区的各个组成部分所发挥的生态作用，以及与他们的相互作用和生理特征，使这个社区持续相关的生物过程。 我实验室以前的生态学工作强调了在细胞生物学方面进行更多基础研究的必要性。这项研究将利用以前成功使用的技术，包括透射电子显微镜和共聚焦显微镜。这项工作将强调褐藻细胞壁的细胞生物学，并将其整合到纯粹和应用研究背景下对褐藻细胞壁的更全面理解中。一个研究组成部分将解决来自棕色真菌的商业产品的特性是否确实基于棕色真菌，或者它们是否来自共生真菌。这将通过比较三种相关的岩藻类物种的商业和“自制”提取物来完成，其中两种物种（Ascophyllum和Pelvetia canaliculata）具有相同的真菌内共生体，而一种物种不具有相同的真菌内共生体（墨角藻（Fucus vesiculosus））。几种共生体（即脊椎动物、Elachista和Mycophycias）穿透宿主组织并造成轻微至严重的损伤，包括局部细胞死亡和宿主组织的严重溶解。这些过程将探索使用免疫标记和电子显微镜，以评估物种之间的相互作用，在不断变化的细胞壁结构和组成的背景下。 尽管它的营养体寿命长，但在外部叶状体壁的脱落和再生过程中，Ascophyllum不断地分解和重组其细胞壁。每年，这释放约10%的生物量作为碎屑。这种脱落过程发生在所有的营养轴和生殖结构上。引起坍塌的化学触发剂将是这项工作的重点。此外，在生殖体（即花托）成熟期间，Ascophyllum经历主要壁溶解。本研究将通过关注细胞壁破裂和程序性细胞死亡的细胞生物学来研究成熟过程。

For the last 30 years my research has had a primary focus of the biology of the economically important brown seaweed Ascophyllum nodosum. This alga has unique biological properties: it is both extremely long-lived (potentially 100 years), and has an ecology that makes it a foundation species in the intertidal zone throughout the cold temperate waters of the North Atlantic Ocean. Ascophyllum is the primary host of a complex symbiotic community that includes two obligate red algae (Vertebrata lanosa, Choreocolax polysiphoniae), a systemic obligate fungus (Mycophycias ascophylli), and a facultative epiphytic brown algae (Elachista fucicola) with its associated marine insect (Halocladius variabilis).  My work has largely involved developing an understanding of the symbiotic associations and the ecological roles played by individual components of this community, and the biological processes associated with their interactions and physiological features that allow this community to persist.        Previous ecological work in my laboratory highlighted the need for more fundamental studies in cell biology. This research will make use of techniques successfully used previously, including transmission electron microscopy and confocal microscopy. The work will emphasize the cell biology of brown algal cell walls, and integrate this into a more comprehensive understanding of brown algal cell walls in the context of both pure and applied research. One research component will address whether or not the properties of commercial products derived from the brown alga are indeed based on the brown alga, or whether they are derived from the symbiotic fungus. This will be done by comparing commercial and `home-made' extracts of three related fucoid species of which two species (Ascophyllum and Pelvetia canaliculata) have the same fungal endosymbiont, and one species which does not (Fucus vesiculosus). Several of the symbionts (i.e. Vertebrata, Elachista and Mycophycias) penetrate the host tissue and cause minimal to major damage including localized cell death, and major dissolution of host tissue. These processes will be explored using immunolabelling and electron microscopy to evaluate interactions between species in the context of changing cell wall structure and composition.      Despite its long-lived vegetative thallus, Ascophyllum is continuously breaking down and reforming its cell walls in a process of sloughing and regeneration of the external thallus wall. Annually, this releases about 10% of the standing biomass as detritus. This sloughing process occurs on all vegetative axes and reproductive structures. The chemical triggers that induce sloughing will be a focus of this work. In addition, during maturation of reproductive bodies (i.e. receptacles) Ascophyllum undergoes major wall dissolution. This research will investigate the maturation process by focusing on the cell biology of cell wall breakdown and programmed cell death.