Messages Do Diffuse Faster than Messengers: Reconciling Disparate Estimates of the Morphogen Bicoid Diffusion Coefficient

• DOI: 10.1371/journal.pcbi.1003629
• Publication Date: 2014-06-05T20:32:04Z
• Authors: Lorena Sigaut; John E. Pearson; Alejandro Colman-...; Silvina Ponce Dawson
• Keywords: Morphogen; Photobleaching; Drosophila embryogenesis; Concentration gradient; Fluorescence Correlation Spectroscopy

The gradient of Bicoid (Bcd) is key for the establishment anterior-posterior axis in Drosophila embryos. properties are compatible with SDD model which Bcd synthesized at anterior pole and then diffuses into embryo degraded a characteristic time. Within this model, diffusion coefficient critical to set timescale formation. This has been measured using two optical techniques, Fluorescence Recovery After Photobleaching (FRAP) Correlation Spectroscopy (FCS), obtaining estimates FCS value an order magnitude larger than FRAP one. discrepancy raises following questions: estimate "correct''; what reason disparity; can explain formation within experimentally observed times? In paper, we use simple biophysical interacts binding sites show that both may be correct arises from fact report on different effective (concentration dependent) coefficients, one describes spreading rate individual molecules (the messengers) other their concentration message). latter more relevant its times.