The role of the prothoracic gland in determining critical weight to metamorphosis in Drosophila melanogaster
The role of the prothoracic gland in determining critical weight to metamorphosis in Drosophila melanogaster
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DOI：
10.1016/j.cub.2005.09.017
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发表时间：
2005-10-25
期刊：
影响因子：
9.2
通讯作者：
Riddiford, LM
中科院分区：
文献类型：
--
作者：
Mirth, C;Truman, JW;Riddiford, LM
背景：全变态昆虫变态的适时开始取决于它们达到被称为临界重量的适当大小。一旦达到临界体重，保幼激素（JH）滴度下降，导致在下一个光周期门释放促前胸腺激素（PTTH），从而诱导变态。个体如何确定何时达到临界体重尚不清楚。我们目前的证据表明，在果蝇，环腺的一个组成部分，前胸腺（PG），评估增长，以确定何时达到临界体重。结果如下：我们使用GAL 4/UAS系统抑制或增强生长过度表达的PTEN或Dp 110，分别在各个组成部分的环腺。抑制生长的PG和CA，但不是单独的CA，产生大于正常的幼虫和成虫。仅PG生长抑制导致无活力的幼虫，但扩大PG的幼虫产生显着较小的幼虫和成虫。饲养幼虫扩大PG在恒定的光增强这些效果，提示光周期门控PTTH分泌的作用。这些幼虫较小，部分原因是它们的生长速度受到抑制，这种表型可以通过营养补充（酵母膏）来拯救。最重要的是，扩大PG的幼虫高估的大小，使他们开始变态之前，超过最低可行的重量需要生存化蛹。结论：PG作为一个大小评估组织，使用胰岛素依赖性PG细胞生长，以确定何时达到临界重量。
Background: The timely onset of metamorphosis in holometabolous insects depends on their reaching the appropriate size known as critical weight. Once critical weight is reached, juvenile hormone (JH) titers decline, resulting in the release of prothoracicotropic hormone (PTTH) at the next photoperiod gate and thereby inducing metamorphosis. How individuals determine when they have reached critical weight is unknown. We present evidence that in Drosophila, a component of the ring gland, the prothoracic gland (PG), assesses growth to determine when critical weight has been achieved. Results: We used the GAL4/UAS system to suppress or enhance growth by overexpressing PTEN or Dp110, respectively, in various components of the ring gland. Suppression of the growth of the PG and CA, but not of the CA alone, produced larger-than-normal larvae and adults. Suppression of only PG growth resulted in nonviable larvae, but larvae with enlarged PGs produced significantly smaller larvae and adults. Rearing larvae with enlarged PGs under constant light enhanced these effects, suggesting a role for photoperiod-gated PTTH secretion. These larvae are smaller, in part as a result of their repressed growth rates, a phenotype that could be rescued through nutritional supplementation (yeast paste). Most importantly, larvae with enlarged PGs overestimated size so that they initiated metamorphosis before surpassing the minimal viable weight necessary to survive pupation. Conclusions: The PG acts as a size-assessing tissue by using insulin-dependent PG cell growth to determine when critical weight has been reached.