Morris Valerie Brett, Byrne Maria
Biological Sciences A12, University of Sydney, NSW 2006, Australia.
J Exp Zool B Mol Dev Evol. 2005 Sep 15;304(5):456-67. doi: 10.1002/jez.b.21065.
The expression of Hox11/13 and Hox5 orthologues in the adult echinoid rudiment in the vestibula larva of Holopneustes purpurescens is described from whole mounts and sections of whole mounts after mRNA in situ hybridization. The Hox5 orthologue is HpHox5, which was isolated here. The expression of HpHox11/13 in the epithelium of the vestibule is aboral to the expression of HpHox5. HpHox5 is expressed in the epithelium of the vestibule floor where the secondary podia develop. The expression of HpHox11/13 and HpHox5 contrasts with the expression of an Otx orthologue, HprOtx, in the circum-oral nerve ring, the radial nerves and the neuroepithelium around the bases of the primary podia. From the expression patterns, we conclude that the two Hox genes are involved in the growth of a metameric series of secondary podia from a growth zone aboral to each primary podium, with the older podia nearer the circum-oral nerve ring. With respect to echinoderm body-plan polarities, we conclude that the growth zone is posterior relative to the anterior circum-oral nerve ring. The metamerism generated in this echinoderm from a posterior growth zone thus might not be generated differently from the way it is generated in bilateral animals.
通过紫海胆前庭幼虫成虫期海胆幼体的整体标本及整体标本切片的mRNA原位杂交，描述了Hox11/13和Hox5直系同源基因的表达情况。Hox5直系同源基因是HpHox5，它是在此分离得到的。HpHox11/13在前庭上皮中的表达位于HpHox5表达的反口面。HpHox5在前庭底部上皮中表达，此处会发育出次生管足。HpHox11/13和HpHox5的表达与Otx直系同源基因HprOtx在围口神经环、辐神经以及初级管足基部周围神经上皮中的表达形成对比。从表达模式来看，我们得出结论，这两个Hox基因参与了从每个初级管足反口面的生长区发育出一系列分节的次生管足的过程，较老的管足更靠近围口神经环。关于棘皮动物身体模式的极性，我们得出结论，相对于前围口神经环，生长区位于后方。因此，这种棘皮动物从后方生长区产生的分节现象，其产生方式可能与两侧对称动物并无不同。
