Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America.
PLoS One. 2007 Sep 12;2(9):e866. doi: 10.1371/journal.pone.0000866.
Differential enlargement of hind (T3) legs represents one of the hallmarks of insect evolution. However, the actual mechanism(s) responsible are yet to be determined. To address this issue, we have now studied the molecular basis of T3 leg enlargement in Oncopeltus fasciatus (milkweed bug) and Acheta domesticus (house cricket). In Oncopeltus, the T3 tibia displays a moderate increase in size, whereas in Acheta, the T3 femur, tibia, and tarsus are all greatly enlarged. Here, we show that the hox gene Ultrabithorax (Ubx) is expressed in the enlarged segments of hind legs. Furthermore, we demonstrate that depletion of Ubx during embryogenesis has a primary effect in T3 legs and causes shortening of leg segments that are enlarged in a wild type. This result shows that Ubx is regulating the differential growth and enlargement of T3 legs in both Oncopeltus and Acheta. The emerging view suggests that Ubx was co-opted for a novel role in regulating leg growth and that the transcriptional modification of its expression may be a universal mechanism for the evolutionary diversification of insect hind legs.
后（T3）肢的差异增大是昆虫进化的标志之一。然而，负责的实际机制尚待确定。为了解决这个问题，我们现在研究了 Oncopeltus fasciatus（乳草蝽）和 Acheta domesticus（家蟋蟀）中 T3 腿增大的分子基础。在 Oncopeltus 中，T3 胫骨的大小适度增加，而在 Acheta 中，T3 股骨、胫骨和跗骨都大大增大。在这里，我们表明 hox 基因 Ultrabithorax（Ubx）在后腿的增大部分表达。此外，我们证明胚胎发生期间 Ubx 的耗竭主要影响 T3 腿，并导致在野生型中增大的腿段缩短。这一结果表明 Ubx 调节 Oncopeltus 和 Acheta 中 T3 腿的差异生长和增大。新兴的观点表明，Ubx 被共同用于调节腿部生长的新角色，并且其表达的转录修饰可能是昆虫后肢进化多样化的普遍机制。
