Maintaining robust size across environmental conditions through plastic growth dynamics

Organ growth is tightly regulated across environmental conditions to generate appropriate final size. While the size of some organs is free to vary, others need to maintain constant size to function properly. This poses a unique problem: how is robust final size achieved when environmental conditions can alter some major growth processes? While we know that brain growth is "spared" from the effects of the environment from humans to fruit flies, we do not understand how this process alters growth dynamics across brain compartments. Here, we explore how this robustness in brain size is achieved by examining differences in growth patterns between the larval body, the brain, and a brain compartment - the mushroom bodies - in Drosophila melanogaster across both thermal and nutritional conditions. We identify key differences in patterns of growth between the whole brain and mushroom bodies that are likely to underlie robustness of final organ shape. Further, we show that these differences produce distinct brain shapes across environments. Significance of StudyA long-standing question in Biology has been how fully functional multicellular organisms with highly specialized organs are generated, given that organs initiate growth at different times across development. Although the genetic mechanisms that underlie growth has been studied extensively, we are yet to understand how growth pattern of organs produces distinct final shapes across changing environmental conditions. We use the Drosophila brain, to reveal that key differences in growth dynamics are likely to underlie robustness of final organ shape and are tuned by nutrition and temperature. Further deepening our knowledge of how final organ shape is maintained across environmental conditions.