Lauzon Robert J, Kidder Sarah J, Long Patricia
Department of Biological Sciences, Union College, Schenectady, NY 12308, USA.
Dev Biol. 2007 Jan 1;301(1):92-105. doi: 10.1016/j.ydbio.2006.08.055. Epub 2006 Aug 30.
The survival of animal tissues and organs is controlled through both activation and suppression of programmed cell death. In the colonial urochordate Botryllus schlosseri, the entire parental generation of zooids in a colony synchronously dies every week as the asexually derived generation of buds reaches functional maturity. This process, called takeover, involves massive programmed cell death (PCD) of zooid organs via apoptosis followed by programmed removal of cell corpses by blood phagocytes within approximately 1 day. We have previously reported that developing buds in conjunction with circulating phagocytes are key effectors of zooid resorption and macromolecular recycling during takeover, and as such engineer the reconstitution of a functional asexual generation every week [Lauzon, R.J., Ishizuka, K.J., Weissman, I.L., 2002. Cyclical generation and degeneration of organs in a colonial urochordate involves crosstalk between old and new: a model for development and regeneration. Dev. Biol. 249, 333-348]. Here, we demonstrate that zooid lifespan during cyclic blastogenesis is regulated by two independent signals: a bud-independent signal that activates zooid PCD and a bud-dependent, survival signal that acts in short-range fashion via the colonial vasculature. As zooids represent a transient, mass-produced commodity during Botryllus asexual development, PCD regulation in this animal via both activation and suppression enables it to remove and recycle its constituent zooids earlier when intra-colony resources are low, while maintaining the functional filter-feeding state when resources are adequate. We propose that this crosstalk mechanism between bud and parent optimizes survival of a B. schlosseri colony with each round of cyclic blastogenesis.
动物组织和器官的存活是通过程序性细胞死亡的激活和抑制来控制的。在群体尾索动物博特瑞利斯 schlosseri 中，群体中亲代一代的所有个体每周会同步死亡，因为无性繁殖产生的芽体一代达到功能成熟。这个过程称为接管，涉及个体器官通过凋亡进行大量程序性细胞死亡（PCD），随后在大约 1 天内由血液吞噬细胞对细胞尸体进行程序性清除。我们之前报道过，发育中的芽体与循环中的吞噬细胞一起，是接管过程中个体吸收和大分子循环利用的关键效应器，因此每周构建一个功能性无性繁殖代 [劳宗，R.J.，石冢，K.J.，魏斯曼，I.L.，2002 年。群体尾索动物器官的周期性产生和退化涉及新旧之间的相互作用：发育和再生的模型。发育生物学。249，333 - 348]。在这里，我们证明了在周期性芽殖过程中个体寿命受两个独立信号调节：一个激活个体 PCD 的与芽体无关的信号，以及一个通过群体脉管系统以短程方式起作用的依赖芽体的存活信号。由于在博特瑞利斯无性发育过程中个体代表一种短暂的、大量产生的产物，通过激活和抑制对该动物的 PCD 进行调节，使其能够在群体内资源不足时更早地清除和循环其组成个体，而在资源充足时维持功能性滤食状态。我们提出，芽体与亲代之间的这种相互作用机制在每一轮周期性芽殖过程中优化了博特瑞利斯 schlosseri 群体的存活。
