The Dl gradient is modulated by changes in nuclear size and density.
A–C) Increasing nuclear size and decreasing nuclei density from haploids (ssm, B) to diploids (A) to triploids (gyn, C) stained with anti-laminin (magenta). D–F) Normalized graphs showing distinct Dl gradient shapes from D. melanogaster (D), ssm (E) and gyn (F, mean±SD). G–J) Cross-section schemes for wild type (G), ssm (H) and gyn (I), and a D. melanogaster embryo (J) representing the Toll signaling gradient. K) Simulated Toll signaling gradient based on the equation for kD, the space-dependent Dl-Cactus dissociation constant. As illustrated in (J), nuclei density affects the angle subtended by 30 cells in a cross-section, resulting in a larger rate of Toll signal decay for gyn and a smaller rate for ssm. (L) Normalized Toll signaling gradients, emphasizing the relationship between the simulated Toll signaling gradient and experimental Dl gradients. Figures (A–F) were modified from ; V, ventral midline; color-coded arrowheads in D–J delimit the 30 ventral most cells.