Usui Kazuya, Pistillo Daniela, Simpson Pat
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, United Kingdom.
Curr Biol. 2004 Jun 22;14(12):1047-55. doi: 10.1016/j.cub.2004.06.026.
Genes of the achaete-scute complex encode transcription factors whose activity regulates the development of neural cells. The spatially restricted expression of achaete-scute on the mesonotum of higher flies governs the development and positioning of the large sensory bristles. On the scutum the bristles are arranged into conserved patterns, based on an ancestral arrangement of four longitudinal rows. This pattern appears to date back to the origin of cyclorraphous flies about 100-140 million years ago. The origin of the four-row bauplan, which is independent of body size, and the reasons for its conservation, are not known.
We report that tendons for attachment of the indirect flight muscles are invariably located between the bristle rows of the scutum throughout the Diptera. Tendon development depends on the activity of a transcription factor encoded by the gene stripe. In Drosophila, stripe and achaete-scute have separate expression domains, leading to spatial segregation of tendon precursors and bristle precursors. Furthermore the products of these genes act antagonistically: ectopic sr expression prevents bristle development and ectopic sc expression prevents normal muscle attachment. The product of stripe acts downstream of Achaete-Scute and interferes with the development of bristle precursors.
The pattern of flight muscles has changed little throughout the Diptera and we argue that the sites of muscle attachment may have constrained the positioning of bristles during the course of evolution. This could account for the pattern of four bristle rows on the scutum.
achaete - scute复合体的基因编码转录因子,其活性调节神经细胞的发育。achaete - scute在高等果蝇中胸背板上的空间限制性表达控制着大型感觉刚毛的发育和定位。在盾片上,刚毛基于四条纵向排的祖先排列方式排列成保守模式。这种模式似乎可以追溯到约1亿至1.4亿年前环裂亚目果蝇的起源。四排体节模式的起源独立于体型大小,其保守的原因尚不清楚。
我们报告,在整个双翅目中,间接飞行肌附着的腱总是位于盾片的刚毛排之间。腱的发育依赖于由stripe基因编码的转录因子的活性。在果蝇中,stripe和achaete - scute有不同的表达域,导致腱前体和刚毛前体的空间分离。此外,这些基因的产物起拮抗作用:异位的sr表达阻止刚毛发育,异位的sc表达阻止正常的肌肉附着。stripe的产物在Achaete - Scute的下游起作用,并干扰刚毛前体的发育。
在整个双翅目中,飞行肌的模式变化很小,我们认为在进化过程中,肌肉附着位点可能限制了刚毛的定位。这可以解释盾片上四排刚毛的模式。