Percival-Smith Anthony, Teft Wendy A, Barta Jodi Lynn
Department of Biology, University of Western Ontario, London, Canada.
Genome. 2005 Aug;48(4):712-21. doi: 10.1139/g05-021.
Arista versus tarsus determination is well investigated in Drosophila, yet it remains unresolved whether Antennapedia (ANTP) cell autonomously or noncell autonomously determines tarsus identity and whether Sex combs reduced (SCR) is the HOX protein required for normal tarsus determination. Three observations rule out a cell autonomous role for ANTP in tarsus determination. (i) Clonal ectopic overexpression of ANTP did not repress the expression of the arista determining protein Homothorax (HTH) in early 3rd stadium antennal imaginal discs. (ii) Clonal ectopic expression of ANTP did not transform the arista to a tarsus. (iii) Ectopic overexpression of ANTP, Labial (LAB), Deformed (DFD), SCR, Ultrabithorax (UBX), Abdominal-A (ABD-A), or Abdominal-B (ABD-B), using the dppGAL4 driver, resulted in arista-to-tarsus transformations, and repressed HTH/Extradenticle (EXD) activity noncell autonomously in early 3rd stadium antennal imaginal discs. SCR may not be the HOX protein required for normal tarsus determination, because co-ectopic expression of Proboscipedia (PB) inhibited the arista-to-tarsus transformations induced by ectopic expression of DFD, SCR, ANTP, UBX, ABD-A, and ABD-B. The proposal that SCR is the HOX protein required for normal tarsus determination is dependent on SCR being the sole target of PB suppression, which is not the case. Therefore, the possibility exists that normal tarsus determination is HOX independent.
在果蝇中，触角芒与跗节的决定机制已得到充分研究，但触角足（ANTP）是通过细胞自主还是非细胞自主方式决定跗节特征，以及性梳减少（SCR）是否为正常跗节决定所需的同源异型盒（HOX）蛋白，这些问题仍未解决。三项观察结果排除了ANTP在跗节决定中发挥细胞自主作用的可能性。（i）在第三龄早期触角成虫盘，ANTP的克隆异位过表达并未抑制触角芒决定蛋白同胸（HTH）的表达。（ii）ANTP的克隆异位表达并未将触角芒转变为跗节。（iii）使用dppGAL4驱动子异位过表达ANTP、唇（LAB）、变形（DFD）、SCR、超双胸（UBX）、腹A（ABD - A）或腹B（ABD - B），导致触角芒向跗节转变，并在第三龄早期触角成虫盘中非细胞自主地抑制HTH/额外触角（EXD）活性。SCR可能不是正常跗节决定所需的HOX蛋白，因为触角足（PB）的共异位表达抑制了由DFD、SCR、ANTP、UBX、ABD - A和ABD - B的异位表达诱导的触角芒向跗节的转变。认为SCR是正常跗节决定所需的HOX蛋白这一观点，依赖于SCR是PB抑制的唯一靶点，但实际并非如此。因此，正常跗节决定可能不依赖于HOX蛋白。
