Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543 USA
Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543 USA.
J Cell Sci. 2018 Apr 10;131(7):jcs212233. doi: 10.1242/jcs.212233.
Microscopic green algae inhabiting desert microbiotic crusts are remarkably diverse phylogenetically, and many desert lineages have independently evolved from aquatic ancestors. Here we worked with five desert and aquatic species within the family Scenedesmaceae to examine mechanisms that underlie desiccation tolerance and release of unicellular versus multicellular progeny. Live cell staining and time-lapse confocal imaging coupled with transmission electron microscopy established that the desert and aquatic species all divide by multiple (rather than binary) fission, although progeny were unicellular in three species and multicellular (joined in a sheet-like coenobium) in two. During division, Golgi complexes were localized near nuclei, and all species exhibited dynamic rotation of the daughter cell mass within the mother cell wall at cytokinesis. Differential desiccation tolerance across the five species, assessed from photosynthetic efficiency during desiccation/rehydration cycles, was accompanied by differential accumulation of intracellular reactive oxygen species (ROS) detected using a dye sensitive to intracellular ROS. Further comparative investigation will aim to understand the genetic, ultrastructural and physiological characteristics supporting unicellular versus multicellular coenobial morphology, and the ability of representatives in the Scenedesmaceae to colonize ecologically diverse, even extreme, habitats.
生活在沙漠微生物结皮中的微观绿藻在系统发育上具有显著的多样性，许多沙漠谱系独立地从水生祖先进化而来。在这里，我们研究了五个属于 Scenedesmaceae 科的沙漠和水生物种，以研究支持耐旱性和释放单细胞与多细胞后代的机制。活细胞染色和延时共聚焦成像结合透射电子显微镜建立了，尽管在三个物种中，后代是单细胞的，而在两个物种中，后代是多细胞的（连接成片状的群体）。在分裂过程中，高尔基体被定位在细胞核附近，所有物种在胞质分裂过程中都表现出母细胞壁内的子细胞团的动态旋转。通过对干燥/复水循环过程中的光合作用效率进行评估，对五种物种的差异耐旱性进行了评估，同时使用对细胞内 ROS 敏感的染料检测到细胞内活性氧物质 (ROS) 的差异积累。进一步的比较研究将旨在了解支持单细胞与多细胞群体形态的遗传、超微结构和生理特征，以及 Scenedesmaceae 代表物种在生态多样化、甚至极端生境中的定殖能力。
