title: A Model of Chloroplast Growth Regulation in Mesophyll Cells.
abstract: Chloroplasts regulate their growth to optimize photosynthesis. Quantitative data show that the ratio of total chloroplast area to mesophyll cell area is constant across different cells within a single species and also across species. Wild-type chloroplasts exhibit little scatter around this trend; highly irregularly shaped mutant chloroplasts exhibit more scatter. Here we propose a model motivated by a bacterial quorum-sensing model consisting of a switch-like signaling network that turns off chloroplast growth. We calculated the dependence of the location of the relevant saddle-node bifurcation on the geometry of the chloroplasts. Our model exhibits a linear trend, with linearly growing scatter dependent on chloroplast shape, consistent with the data. When modeled chloroplasts are of a shape that grows with a constant area-to-volume ratio (disks, cylinders), we find a linear trend with minimal scatter. Chloroplasts with area and volume that do not grow proportionally (spheres) exhibit a linear trend with additional scatter.
authors.affiliation: Institute of Applied Mathematics, University of British Columbia, Vancouver, Canada.
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Paton
authors.affiliation: Institute of Applied Mathematics, University of British Columbia, Vancouver, Canada.
authors.forename: Lisa
authors.initials: L
authors.lastname: Anderson
authors.affiliation: Institute of Applied Mathematics, University of British Columbia, Vancouver, Canada.
authors.forename: Pauline
authors.initials: P
authors.lastname: Flottat
authors.affiliation: Institute of Applied Mathematics, University of British Columbia, Vancouver, Canada. cytryn@math.ubc.ca.|Department of Mathematics, University of British Columbia, Vancouver, Canada. cytryn@math.ubc.ca.
authors.forename: Eric N
authors.initials: EN
authors.lastname: Cytrynbaum
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D002736:Chloroplasts / Q000378:metabolism / Q000648:ultrastructure*; D055641:Mathematical Concepts; D058503:Mesophyll Cells / Q000378:metabolism / Q000648:ultrastructure*; D008954:Models, Biological; D010788:Photosynthesis; D015398:Signal Transduction
keywords: Bifurcation; Chloroplasts; Growth regulation; Model; Ordinary differential equations; Switch