Carbon dioxide is an important environmental cue for many insects, regulating many behaviors including some that have direct human impacts. To further improve our understanding of how this system varies among closely related insect species, we examined both the behavioral response to CO₂ as well as the transcriptional profile of key developmental regulators of CO₂ sensory neurons in the olfactory system across the Drosophila genus. We found that CO₂ generally evokes repulsive behavior across most of the Drosophilids we examined, but this behavior has been lost or reduced in several lineages. Comparisons of transcriptional profiles from the developing and adult antennae for subset these species suggest that behavioral differences in some species may be due to differences in the expression of the CO₂ co-receptor Gr63a. Furthermore, these differences in Gr63a expression are correlated with changes in the expression of a few genes known to be involved in the development of the CO₂ circuit, namely dac, an important regulator of sensilla fate for sensilla that house CO₂ ORNs, and mip120, a member of the MMB/dREAM epigenetic regulatory complex that regulates CO₂ receptor expression. In contrast, most of the other known structural, molecular, and developmental components of the peripheral Drosophila CO₂ olfactory system seem to be well-conserved across all examined lineages. These findings suggest that certain components of CO₂ sensory ORN development may be more evolutionarily labile, and may contribute to differences in CO₂-evoked behavioral responses across species.

二氧化碳是许多昆虫的重要环境线索，它控制着许多行为，包括直接影响人类的行为。为了进一步提高我们对这个系统在紧密相关的昆虫物种之间如何变化的理解，我们检查了果蝇属嗅系统中对CO ₂的行为响应以及CO ₂感觉神经元关键发育调节因子的转录谱。我们发现CO ₂通常会引起我们检查过的大多数果蝇的排斥行为，但是这种行为在多个血统中已经消失或减少。比较来自发育触角和成虫触角的亚种这些物种的转录谱，表明某些物种的行为差异可能是由于CO ₂共受体Gr63a表达的差异所致。此外，Gr63a表达的这些差异与一些已知与CO ₂回路发育有关的基因的表达变化相关，即dac（容纳CO ₂ ORN的感觉分子的重要感觉调控因子），mip120。是MMB / dREAM表观遗传调控复合物的成员，该复合物调控CO ₂受体表达。相反，周围果蝇CO ₂嗅觉系统的大多数其他已知的结构，分子和发育成分似乎在所有检查的谱系中都保存良好。这些发现表明，CO ₂感官ORN发育的某些成分可能在进化上更加不稳定，并且可能导致物种间CO ₂诱发的行为反应的差异。