Sköld Helen Nilsson, Stach Thomas, Bishop John D D, Herbst Eva, Thorndyke Michael C
Marine Ecology-Kristineberg, University of Gothenburg, Fiskebäckskil, Sweden.
Biol Bull. 2011 Aug;221(1):126-36. doi: 10.1086/BBLv221n1p126.
Many invertebrates reproduce asexually by budding, but morphogenesis and the role of cell proliferation in this diverse and nonconserved regeneration-like process are generally poorly understood and particularly little investigated in didemnid ascidians. We here analyzed cell proliferation patterns and telomerase activity during budding in the colonial didemnid ascidian Diplosoma listerianum, with special focus on the thoracic bud where a new brain develops de novo. To help define developmental stages of the thoracic bud, the distribution of acetylated tubulin was also examined. We found extensive cell proliferation in both the thoracic and abdominal buds of D. listerianum as well as higher telomerase activity in bud tissue compared to adult tissues. In the parent adult, proliferation was found in various tissues, but was especially intense in the adult esophagus and epicardial structures that protrude into the proliferating and developing buds, confirming these tissues as the primary source of the cells that form the buds. The neural complex in the thoracic bud forms from a hollow tube that appears to separate into the neural gland and the cerebral ganglion. Whereas most of the bud undergoes proliferation, including the hollow tube and the neural gland, the cerebral ganglion shows little or no proliferation. Pulse-chase labeling experiments indicate that the ganglion, as well as the myocardium, in adult zooids are instead composed of postmitotic cells.
许多无脊椎动物通过出芽进行无性繁殖，但在这种多样且非保守的类似再生过程中，形态发生和细胞增殖的作用通常了解甚少，在双体海鞘中尤其缺乏研究。我们在此分析了群体双体海鞘利氏 Diplosoma listerianum 出芽过程中的细胞增殖模式和端粒酶活性，特别关注新脑从头发育的胸芽。为了帮助确定胸芽的发育阶段，还检查了乙酰化微管蛋白的分布。我们发现利氏 Diplosoma listerianum 的胸芽和腹芽中都有广泛的细胞增殖，并且与成体组织相比，芽组织中的端粒酶活性更高。在亲代成体中，在各种组织中都发现了增殖，但在伸入增殖和发育芽体的成体食管和心外膜结构中尤其强烈，证实这些组织是形成芽体的细胞的主要来源。胸芽中的神经复合体由一个似乎分离成神经腺和脑神经节的空心管形成。虽然大多数芽体都会增殖，包括空心管和神经腺，但脑神经节几乎没有或没有增殖。脉冲追踪标记实验表明，成年游动孢子中的神经节以及心肌反而由有丝分裂后细胞组成。
