Choe Chong Pyo, Brown Susan J
Division of Biology, Kansas State University, Manhattan, KS 66506, USA.
Dev Biol. 2009 Jan 15;325(2):482-91. doi: 10.1016/j.ydbio.2008.10.037. Epub 2008 Nov 6.
In Drosophila, primary pair-rule genes establish the parasegmental boundaries and indirectly control the periodic expression of the segment polarity genes engrailed (en) and wingless (wg) via regulation of secondary pair-rule genes. Although orthologs of some Drosophila pair-rule genes are not required for proper segmentation in Tribolium, segmental expression of Tc-en and Tc-wg is conserved. To understand how these segment polarity genes are regulated, we examined the results of expressing one or two pair-rule genes in the absence of the other known pair-rule genes. Expression of one or both of the secondary pair-rule genes, Tc-sloppy-paired (Tc-slp) and Tc-paired (Tc-prd), activated Tc-wg in the absence of the primary pair-rule genes, Tc-even-skipped (Tc-eve), Tc-runt (Tc-run) and Tc-odd-skipped (Tc-odd). Tc-eve alone failed to activate Tc-wg or Tc-en, but in combination with Tc-run or Tc-prd activated Tc-en. These results, interpreted within the pair-rule gene expression patterns, suggest separate models for the genetic regulation of the juxtaposed expression of Tc-wg and Tc-en at odd- and even-numbered parasegmental boundaries, respectively. Conserved interactions between eve and prd at the anterior boundary of odd-numbered parasegments may reflect an ancestral segmentation mechanism that functioned in every segment prior to the evolution of pair-rule segmentation.
在果蝇中，初级成对规则基因确立了副节边界，并通过调控次级成对规则基因间接控制节段极性基因 engrailed（en）和 wingless（wg）的周期性表达。尽管某些果蝇成对规则基因的直系同源基因对于赤拟谷盗的正常分节并非必需，但 Tc-en 和 Tc-wg 的节段性表达是保守的。为了了解这些节段极性基因是如何被调控的，我们研究了在其他已知成对规则基因缺失的情况下表达一个或两个成对规则基因的结果。在初级成对规则基因 Tc-even-skipped（Tc-eve）、Tc-runt（Tc-run）和 Tc-odd-skipped（Tc-odd）缺失的情况下，次级成对规则基因 Tc-sloppy-paired（Tc-slp）和 Tc-paired（Tc-prd）中的一个或两个的表达激活了 Tc-wg。单独的 Tc-eve 未能激活 Tc-wg 或 Tc-en，但与 Tc-run 或 Tc-prd 结合时则激活了 Tc-en。这些结果，结合成对规则基因的表达模式来解释，分别为 Tc-wg 和 Tc-en 在奇数和偶数副节边界并列表达的遗传调控提出了不同的模型。奇数副节前边界处 eve 和 prd 之间保守的相互作用可能反映了一种在成对规则分节进化之前在每个节段中起作用的祖先分节机制。
