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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >Inaugural Article: A molt timer is involved in the metamorphic molt in Manduca sexta larvae
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Inaugural Article: A molt timer is involved in the metamorphic molt in Manduca sexta larvae

机译：开篇文章：蜕皮定时器与曼杜卡六倍体幼虫的蜕变蜕变有关

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Manduca sexta larvae are a model for growth control in insects, particularly for the demonstration of critical weight, a threshold weight that the larva must surpass before it can enter metamorphosis on a normal schedule, and the inhibitory action of juvenile hormone on this checkpoint. We examined the effects of nutrition on allatectomized (CAX) larvae that lack juvenile hormone to impose the critical weight checkpoint. Normal larvae respond to prolonged starvation at the start of the last larval stage, by extending their subsequent feeding period to ensure that they begin metamorphosis above critical weight. CAX larvae, by contrast, show no homeostatic adjustment to starvation but start metamorphosis 4 d after feeding onset, regardless of larval size or the state of development of their imaginal discs. By feeding starved CAX larvae for various durations, we found that feeding for only 12–24 h was sufficient to result in metamorphosis on day 4, regardless of further feeding or body size. Manipulation of diet composition showed that protein was the critical macronutrient to initiate this timing. This constant period between the start of feeding and the onset of metamorphosis suggests that larvae possess a molt timer that establishes a minimal time to metamorphosis. Ligation experiments indicate that a portion of the timing may occur in the prothoracic glands. This positive system that promotes molting and the negative control via the critical weight checkpoint provide antagonistic pathways that evolution can modify to adapt growth to the ecological needs of different insects.
机译：Manduca sexta幼虫是控制昆虫生长的模型，尤其是用于证明临界体重，幼虫可以按正常计划进入变态之前必须超过的阈值重量，以及少年激素对该检查点的抑制作用。我们检查了营养对缺乏幼体激素以施加临界体重检查点的异体切除（CAX）幼虫的影响。正常幼体在最后一个幼体阶段开始时对长期饥饿产生反应，方法是延长其随后的摄食期，以确保它们在临界体重以上开始变态。相比之下，CAX幼虫没有表现出对饥饿的稳态调节，而是在进食开始后4 d开始变态，无论幼虫大小或假想盘的发育状态如何。通过喂食饥饿的CAX幼虫不同的时间，我们发现仅喂食12–24 h就足以在第4天导致变态，而与进一步喂食或体型无关。饮食组成的操纵表明蛋白质是启动该时间的关键常量营养素。从开始喂食到变态开始的这段恒定时间表明，幼虫具有蜕皮定时器，该定时器可确定变态的最短时间。结扎实验表明，一部分时间可能发生在胸腺中。这种促进蜕皮的阳性系统和通过临界重量检查点进行的阴性对照提供了拮抗途径，可以改变进化来适应生长，以适应不同昆虫的生态需求。

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