Cell length growth in fission yeast: an analysis of its bilinear character and the nature of its rate change transition

摘要

During their mitotic cycle, cylindrical fission yeast cells grow exclusively at their tips. Length growth starts at birth and halts at mitotic onset when the cells begin to prepare for division. While the growth pattern was initially considered to beexponential, during the last three decades an increasing amount of evidence indicated that it is rather a bilinear function [two linear segments separated by a rate change point (RCP)]. The main focus of this work was to clarify this and to elucidate thefurther question of whether the rate change occurs abruptly at the RCP or more smoothly during a transition period around it. We have analyzed the individual growth patterns obtained by time-lapse microscopy of 60 wild-type cells separately as well as that of the 'average' cell generated from their superposition. Linear, exponential, and bilinear functions were fitted to the data, and their suitability was compared using objective model selection criteria. This analysis found the overwhelming majorityof the cells (70%) to have a bilinear growth pattern with close to half of them showing a smooth and not an abrupt transition. The growth pattern of the average cell was also found to be bilinear with a smooth transition.