How do plant cells measure themselves?

From bacteria to humans, cell size is important for many processes, including exchange of nutrients and signals, cell division, cell longevity and the function of specialized cells. Despite its importance, how cells achieve and maintain their genetically-controlled size has been a long-standing mystery. In proliferating cells, the average size depends on the coordination between cell growth and division. We have been studying this question using plants, in which it is relatively easy to track and measure cell growth and cell division.

In a breakthrough in this field, we found that plant cells adjust their own size using their DNA contents as a "ruler" (DOI: 10.1126/science.abb4348). The mechanism relies on a cell cycle inhibitor called KRP4, which binds to chromosomes before cell division, whilst unbound KRP4 is destroyed by proteolysis. In this way, cells are born with a fixed amount of KRP4, regardless of their size at birth. Consequently, cells grow to the same target size, at which KRP4 is sufficiently diluted to allow progression to the next cell division.

A key part of this mechanism is the ability of KRP4 to interact with chromatin to ensure that it is inherited by cells in proportion to DNA contents. The underlying biochemical mechanism, however, is not known. In this project, the student will investigate the mechanism by which KRP4 interacts with chromatin, how the interactions change during the cell cycle and their consequences for cell size control. The work is expected to illuminate a fundamental aspect of plant development and cell biology, with potential applications for crop growth and productivity.

The successful applicant will join the Sablowski team, which is part of a lively department with multidisciplinary interactions, with strength in predictive, quantitative approaches, and supported by state-of-the-art facilities, particularly for bioimaging.