Transcriptional changes during Daphnia pulex development indicate that the maturation decision resembles a rate more than a threshold

Maturation is a critical developmental process, and the age and size at which it occurs have important fitness consequences. Although maturation is remarkably variable, certain mechanisms, including a minimum size or state threshold, are proposed to underlie the process across a broad diversity of taxa. Recent evidence suggests that thresholds may themselves be developmentally plastic, and in the crustacean Daphnia pulex it is unclear whether maturation follows a threshold or is a gradual process more akin to a rate. Changes in gene expression across four instars before and during maturation were compared in a cDNA microarray experiment. Developmental stage was treated statistically both as a discontinuous and a continuous variable, to determine whether genes showed gradual or discrete changes in expression. The continuous analysis identified a greater number of genes with significant differential expression (45) than the discontinuous analysis (11). The majority of genes, including tho...

成熟是至关重要的发育进程，其发生时的年龄与体型大小对个体适合度（fitness）具有重要的进化效应。尽管成熟过程存在显著的变异，但已有研究提出，包括最小体型或状态阈值在内的若干机制，是广泛分布于各类生物类群的该发育过程的核心基础。近期研究证据表明，阈值本身可能具有发育可塑性；而在甲壳动物蚤状溞（Daphnia pulex）中，目前尚不清楚成熟过程是遵循阈值模式，还是更接近速率依赖的渐进过程。本研究通过cDNA微阵列（cDNA microarray）实验，对比了成熟前及成熟过程中四个龄期的基因表达变化。研究将发育阶段分别以不连续变量和连续变量的形式进行统计学处理，以此判断基因的表达变化是渐进式还是离散式。连续变量分析所鉴定出的显著差异表达基因数量（45个）多于不连续变量分析（11个）。绝大多数基因，包括 tho...