Intracellular Scaling Mechanisms

Abstract

Organelle function is often directly related to organelle size. However, it is not necessarily absolute size but the organelle-to-cell-size ratio that is critical. Larger cells generally have increased metabolic demands, must segregate DNA over larger distances, and require larger cytokinetic rings to divide. Thus, organelles often must scale to the size of the cell. The need for scaling is particularly acute during early development during which cell size can change rapidly. Here, we highlight scaling mechanisms for cellular structures as diverse as centrosomes, nuclei, and the mitotic spindle, and distinguish them from more general mechanisms of size control. In some cases, scaling is a consequence of the underlying mechanism of organelle size control. In others, size-control mechanisms are not obviously related to cell size, implying that scaling results indirectly from cell-size-dependent regulation of sizecontrol mechanisms.

Size Control in Plants—Lessons from Leaves and Flowers

“…However, how this process contributes to coordinating proliferation throughout organ primordia is currently not well understood. The coordinated arrest of cell proliferation (discussed in Reber and Goehring 2015) has been suggested to involve a mobile growth factor distinct from classical phytohormones that would be produced by the cytochrome P450 KLUH/CYP78A5 at the organ periphery and base (Anastasiou et al 2007;Kazama et al 2010). However, as mentioned above, clonal analysis indicates that the range of KLUH action is extending beyond individual organs and is, thus, larger than assumed (Eriksson et al 2010).…”

Cell-Size Control

“…Constant yardsticks are much less common within growing cells because, much like proteins, the majority of organelles scale with cell size (see Marshall 2015; Reber and Goehring 2015). For example, nuclear size relative to that of the cell shows little variation.…”

Biological Scaling Problems and Solutions in Amphibians

“…General mechanisms of subcellular size control are discussed in detail in Marshall (2015) and Reber and Goehring (2015). Amphibians, and Xenopus frogs in particular, have provided unique approaches to elucidate scaling mechanisms, both among species with different-sized cells as well as during development when cleavage divisions rapidly give rise to smaller and smaller cells (Fig.…”