Cell size selection in Chlamydomonas reinhardtii gametes using fluorescence activated cell sorting

Existing approaches to measuring the size of single cells or, alternatively, disrupting the size distributions of populations, do not often allow the high throughput collection and separation of live cells post-measurement. An emerging method for the measurement and collection of single cells based on cellular properties is flow fluorescence activated cell sorting (FACS). Here, we use cell sorting to demonstrate the utility of selecting on size in live gametes of the single celled algae Chlamydomonas reinhardtii; an important model in cell cycle research, cell physiology and biofuel modelling. Using three methods, we demonstrate the capacity to sort live cells without the need for extrinsic fluorophores. By selecting on size related characteristics in gametes, we are able to show the capacity for sensitive selection of small variations in cell size. Furthermore, we demonstrate the use of autofluorescence properties of algae, and further support existing literature showing effective disruptive selection on size when incident light scatter and fluorescence parameters are combined as selection criteria. Estimates demonstrate significant heritability of cell size in both gametes and vegetative cells, while a strong correlation between gametic and vegetative size suggests that selection on gamete size could be used to evolve vegetative size under experimental evolution.