Evolution of maternal control of axial patterning in insects

Positional and cell fate cues provided maternally to eggs are important factors in the development of many animals. The insects are a model clade where maternal establishment of embryonic axes is widespread and has been a topic of intense classical and molecular embryological analysis. Recently, significant progress has been made in revealing the molecular basis of some classical embryological experiments. In addition, observations of novel forms of maternal positional cues have been made. Finally, it has become increasingly clear that no maternal source of positional information acts alone without input and feedback from zygotic target genes to ensure precise and repeatable pattern formation in the early embryo. These advances will be discussed in the context of historical experiments, our current understanding of how positional cues can be generated, stored, and transmitted in insect ovaries and eggs, and how the nature of the cues can change in evolution.