Higher thyroid hormone receptor expression correlates with short larval periods in spadefoot toads and increases metamorphic rate.
Higher thyroid hormone receptor expression correlates with short larval periods in spadefoot toads and increases metamorphic rate.
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DOI：
10.1016/j.ygcen.2011.05.013
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发表时间：
2011-08-01
影响因子：
2.7
通讯作者：
Buchholz, Daniel R.
中科院分区：
文献类型：
--
作者：
Hollar, Amy R.;Choi, Jinyoung;Grimm, Adam T.;Buchholz, Daniel R.
铲足蟾蜍物种显示在幼虫期持续时间的极端变化，部分原因是甲状腺激素（TH）生理的演变。具体而言，沙漠种幼虫期短，具有较高的尾部组织TH含量和表现出增加的响应TH。为了解决幼虫期差异的分子基础，我们研究了TH受体（TR）的跨物种表达。基于TR在发育中作用的双功能模型，我们假设具有短幼虫期的沙漠铲足物种将具有1）在产生内源性TH之前的TR表达的迟发性和2）当内源性TH变得可用时的较高TR水平。为了验证这些假设，我们克隆了沙漠铲足蟾蜍Scaphiopus couchii和Spea multiplicata及其非沙漠亲戚Pelobates cultripes的TRα和TRβ基因片段，并在不存在（变态前）或存在（自然变态）TH的情况下，使用定量PCR测量其尾部的mRNA水平。所有的物种都在最早期（刚孵化后）表达TRα和TRβ，但S.幼虫期最短的库奇虫在整个发育过程中的TRα值高于幼虫期最长的养殖对虾。不同物种间TRβ mRNA水平相似。外源T3处理诱导S.与其他物种相比，couchii的TRα mRNA表达增加，这与其TRα mRNA表达增加一致，并表明在分子水平上TRα活性增加的功能结果。为了直接测试较高的TRα表达是否有助于缩短幼虫期，我们通过质粒注射到模型蛙非洲爪蟾的尾肌细胞中过表达TRα，发现肌细胞死亡率增加对TH的反应。这些结果表明，增加TRα表达进化在S。couchii和有助于其较高的变质率。
Spadefoot toad species display extreme variation in larval period duration, due in part to evolution of thyroid hormone (TH) physiology. Specifically, desert species with short larval periods have higher tail tissue content of TH and exhibit increased responsiveness to TH. To address the molecular basis of larval period differences, we examined TH receptor (TR) expression across species. Based on the dual function model for the role of TR in development, we hypothesized that desert spadefoot species with short larval periods would have 1) late onset of TR expression prior to the production of endogenous TH and 2) higher TR levels when endogenous TH becomes available. To test these hypotheses, we cloned fragments of TRα and TRβ genes from the desert spadefoot toads Scaphiopus couchii and Spea multiplicata and their non-desert relative Pelobates cultripes and measured their mRNA levels in tails using quantitative PCR in the absence (premetamorphosis) or presence (natural metamorphosis) of TH. All species express TRα and TRβ from the earliest stages measured (from just after hatching), but S. couchii, which has the shortest larval period, had more TRα throughout development compared to P. cultripes, which has the longest larval period. TRβ mRNA levels were similar across species. Exogenous T3 treatment induced faster TH-response gene expression kinetics in S. couchii compared to the other species, consistent with its increased TRα mRNA expression and indicative of a functional consequence of more TRα activity at the molecular level. To directly test whether higher TRα expression may contribute to shorter larval periods, we overexpressed TRα via plasmid injection into tail muscle cells of the model frog Xenopus laevis and found an increased rate of muscle cell death in response to TH. These results suggest that increased TRα expression evolved in S. couchii and contribute to its higher metamorphic rates.
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DOI：
10.1073/pnas.90.15.7322
发表时间：
1993-08-01
影响因子：
11.1
作者：
DELUZE, A;SACHS, L;DEMENEIX, B
通讯作者：
DEMENEIX, B
影响因子：
5.3
作者：
Buchholz, DR;Hsia, SCV;Shi, YB
通讯作者：
Shi, YB
影响因子：
10.1
作者：
NEWMAN, RA
通讯作者：
NEWMAN, RA
影响因子：
4.8
作者：
Paul, BD;Buchholz, DR;Shi, YB
通讯作者：
Shi, YB
影响因子：
2.5
作者：
Fu, LZ;Buchholz, D;Shi, YB
通讯作者：
Shi, YB