Noncanonical expression of caudal during early embryogenesis in the pea aphid Acyrthosiphon pisum: maternal cad-driven posterior development is not conserved
Noncanonical expression of caudal during early embryogenesis in the pea aphid Acyrthosiphon pisum: maternal cad-driven posterior development is not conserved
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DOI：
10.1111/imb.12035
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发表时间：
2013-08-01
影响因子：
2.6
通讯作者：
Chang, T-H.
中科院分区：
文献类型：
--
作者：
Chang, C-c.;Hsiao, Y-m.;Chang, T-H.
先前我们在单性生殖和胎生豌豆蚜虫Acyrthosiphon pisum的卵母细胞和早期胚胎中发现了驼背（Aphb） mRNA的前定位，这表明卵母细胞前不对称的打破导致胚胎前轴的形成。为了研究无性豌豆蚜虫的后侧发育，我们克隆并分析了一个在许多动物门中高度保守的后侧基因尾侧（Apcad）的发育表达。我们发现在无性（胎生）豌豆蚜虫胚皮形成之前，Apcad的转录本在德国、卵母细胞和胚胎中未被检测到。这种不寻常的表达模式不同于现有的昆虫模型，包括长胚芽和短胚芽昆虫，其中母体cad mRNA传递到早期胚胎并形成前后梯度。第一个可检测到的Apcad表达出现在新形成的原始生殖细胞及其邻近的囊胚细胞中。从原肠期开始，和其他昆虫一样，Apcad mRNA被限制在胚芽带的最后方区域。同样，在有性（卵生）卵母细胞中，我们能够确定Aphb mRNA的前定位，但未检测到Apcad的后定位。这表明，在无性和有性豌豆蚜虫的早期胚胎发生中，cad驱动的后侧发育并不保守。
Previously we identified anterior localization of hunchback (Aphb) mRNA in oocytes and early embryos of the parthenogenetic and viviparous pea aphid Acyrthosiphon pisum, suggesting that the breaking of anterior asymmetry in the oocytes leads to the formation of the anterior axis in embryos. In order to study posterior development in the asexual pea aphid, we cloned and analysed the developmental expression of caudal (Apcad), a posterior gene highly conserved in many animal phyla. We found that transcripts of Apcad were not detected in germaria, oocytes and embryos prior to the formation of the blastoderm in the asexual (viviparous) pea aphid. This unusual expression pattern differs from that of the existing insect models, including long-and short-germ insects, where maternal cad mRNA is passed to the early embryos and forms a posterior-anterior gradient. The first detectable Apcad expression occurred in the newly formed primordial germ cells and their adjacent blastodermal cells during late blastulation. From gastrulation onward, and as in other insects, Apcad mRNA is restricted to the posteriormost region of the germ band. Similarly, in the sexual (oviparous) oocytes we were able to identify anterior localization of Aphb mRNA but posterior localization of Apcad was not detected. This suggests that cad-driven posterior development is not conserved during early embryogenesis in asexual and sexual pea aphids.