Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-0371, USA.
Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-0371, USA
J Exp Biol. 2018 May 20;221(Pt 10):jeb171967. doi: 10.1242/jeb.171967.
Animal size is a highly variable trait regulated by complex interactions between biological and environmental processes. Despite the importance of understanding the mechanistic bases of growth, predicting size variation in early stages of development remains challenging. Pedigreed lines of the Pacific oyster () were crossed to produce contrasting growth phenotypes to analyze the metabolic bases of growth variation in larval stages. Under controlled environmental conditions, substantial growth variation of up to 430% in shell length occurred among 12 larval families. Protein was the major biochemical constituent in larvae, with an average protein-to-lipid content ratio of 2.8. On average, 86% of protein synthesized was turned over (i.e. only 14% retained as protein accreted), with a regulatory shift in depositional efficiency resulting in increased protein accretion during later larval growth. Variation in protein depositional efficiency among families did not explain the range in larval growth rates. Instead, changes in protein synthesis rates predicted 72% of growth variation. High rates of protein synthesis to support faster growth, in turn, necessitated greater allocation of the total ATP pool to protein synthesis. An ATP allocation model is presented for larvae of that includes the major components (82%) of energy demand: protein synthesis (45%), ion pump activity (20%), shell formation (14%) and protein degradation (3%). The metabolic trade-offs between faster growth and the need for higher ATP allocation to protein synthesis could be a major determinant of fitness for larvae of different genotypes responding to the stress of environmental change.
动物体型是一个高度可变的特征，由生物和环境过程之间的复杂相互作用调节。尽管了解生长的机制基础很重要，但预测早期发育阶段的大小变化仍然具有挑战性。通过杂交太平洋牡蛎的品系，产生了不同的生长表型，以分析幼虫阶段生长变化的代谢基础。在受控的环境条件下，12 个幼虫家系之间的壳长生长差异高达 430%。蛋白质是幼虫的主要生化成分，蛋白质与脂质含量的平均比例为 2.8。平均而言，合成的蛋白质中有 86%被周转（即只有 14%作为蛋白质积累保留），沉积效率的调节转变导致后期幼虫生长过程中蛋白质积累增加。家系间蛋白质沉积效率的差异并不能解释幼虫生长率的变化范围。相反，蛋白质合成率的变化预测了 72%的生长变化。为了支持更快的生长，需要更高的蛋白质合成率，这反过来又需要将总 ATP 池更大比例地分配给蛋白质合成。为幼虫提出了一个 ATP 分配模型，该模型包括能量需求的主要组成部分（82%）：蛋白质合成（45%）、离子泵活性（20%）、壳形成（14%）和蛋白质降解（3%）。在更快的生长和更高的 ATP 分配给蛋白质合成的需求之间的代谢权衡可能是不同基因型幼虫对环境变化压力的适应能力的主要决定因素。
