Control of body size by oxygen supply reveals size-dependent and size-independent mechanisms of molting and metamorphosis
Control of body size by oxygen supply reveals size-dependent and size-independent mechanisms of molting and metamorphosis
复制标题
DOI：
10.1073/pnas.1106556108
复制
发表时间：
2011-08-30
影响因子：
11.1
通讯作者：
Nijhout, H. Frederik
中科院分区：
文献类型：
--
作者：
Callier, Viviane;Nijhout, H. Frederik
体型深刻地影响着动物生物学的许多方面，包括变态、异速生长、体型依赖的基因表达替代途径，以及个体的社会和生态角色。然而，体型的调节是发育生物学中尚未解决的基本问题之一。控制体型需要一种机制来评估体型，并在体型的特征范围内停止生长。在Manduca sexta的正常生长条件下，当幼虫达到临界体重时，导致大脑开始变态的内分泌级联反应开始。变形是由一种尺寸感知机制引起的，但这种机制的性质仍然是难以捉摸的。在这里，我们表明，这种大小感应机制取决于一个固定气管系统的有限能力，以维持氧气供应的成长个体。随着体重的增加，对氧气的需求也会增加，但固定气管系统不允许相应增加氧气供应。我们发现，与蜕变一样，期间蜕皮也具有与大小相关的氧依赖调节机制。我们发现，低氧张力诱导小体长脱毛，这与在正常生长条件下，体长由一种感知氧气限制的机制调节的假设相一致。我们还发现，在生长条件差的情况下，幼虫可能永远达不到临界体重，但最终还是会蜕皮。我们发现，在这些条件下，幼虫不使用临界体重机制，而是使用独立于大脑的大小独立机制。
Body size profoundly affects many aspects of animal biology, including metamorphosis, allometry, size-dependent alternative pathways of gene expression, and the social and ecological roles of individuals. However, regulation of body size is one of the fundamental unsolved problems in developmental biology. The control of body size requires a mechanism that assesses size and stops growth within a characteristic range of sizes. Under normal growth conditions in Manduca sexta, the endocrine cascade that causes the brain to initiate metamorphosis starts when the larva reaches a critical weight. Metamorphosis is initiated by a size-sensing mechanism, but the nature of this mechanism has remained elusive. Here we show that this size-sensing mechanism depends on the limited ability of a fixed tracheal system to sustain the oxygen supply to a growing individual. As body mass increases, the demand for oxygen also increases, but the fixed tracheal system does not allow a corresponding increase in oxygen supply. We show that interinstar molting has the same size-related oxygen-dependent mechanism of regulation as metamorphosis. We show that low oxygen tension induces molting at smaller body size, consistent with the hypothesis that under normal growth conditions, body size is regulated by a mechanism that senses oxygen limitation. We also found that under poor growth conditions, larvae may never attain the critical weight but eventually molt regardless. We show that under these conditions, larvae do not use the critical weight mechanism, but instead use a size-independent mechanism that is independent of the brain.