Formative Cell Divisions: Principal Determinants of Plant Morphogenesis

Abstract

Formative cell divisions utilizing precise rotations of cell division planes generate and spatially place asymmetric daughters to produce different cell layers. Therefore, by shaping tissues and organs, formative cell divisions dictate multicellular morphogenesis. In animal formative cell divisions, the orientation of the mitotic spindle and cell division planes relies on intrinsic and extrinsic cortical polarity cues. Plants lack known key players from animals, and cell division planes are determined prior to the mitotic spindle stage. Therefore, it appears that plants have evolved specialized mechanisms to execute formative cell divisions. Despite their profound influence on plant architecture, molecular players and cellular mechanisms regulating formative divisions in plants are not well understood. This is because formative cell divisions in plants have been difficult to track owing to their submerged positions and imprecise timings of occurrence. However, by identifying a spatiotemporally inducible cell division plane switch system applicable for advanced microscopy techniques, recent studies have begun to uncover molecular modules and mechanisms for formative cell divisions. The identified molecular modules comprise developmentally triggered transcriptional cascades feeding onto microtubule regulators that now allow dissection of the hierarchy of the events at better spatiotemporal resolutions. Here, we survey the current advances in understanding of formative cell divisions in plants in the context of embryogenesis, stem cell functionality and post-embryonic organ formation.

The receptor‐like kinases GSO1 and GSO2 together regulate root growth in arabidopsis through control of cell division and cell fate specification

“…). Cell‐autonomous or short‐distance signaling that activates a multitude of transcription factors further refines meristem activity (Smolarkiewicz and Dhonukshe, ).…”

“…9). Cell-autonomous or shortdistance signaling that activates a multitude of transcription factors further refines meristem activity (Smolarkiewicz and Dhonukshe, 2013). gso1; gso2 double mutant seedling roots arrest growth by three DAG, a phenotype that occurs with three independent combinations of double mutants and does not occur in any of the single mutants.…”

Green Algae and the Origins of Multicellularity in the Plant Kingdom

“…This division of labor serves at least two purposes: First, by partitioning or restricting reproductive capacity to a subset of cells, genetic conflicts associated with a transition of fitness from individual cells to cooperating groups of cells can be mitigated (Michod and Roze 2001). Second, in multicellular organisms with indeterminate body plans such as land plants, vegetative stem cells play a critical role in integrating internal and external signals to regulate and establish overall organismal architecture (Smolarkiewicz and Dhonukshe 2013). …”

“…It is increasingly clear that the path to multicellular evolution is dependent on the genetic and cellular "toolkits" available in unicellular ancestors, as well as on the specific circumstances and environment in which multicellularity arose (Rokas 2008;Knoll 2011;Bowman 2013;Niklas and Newman 2013;Smolarkiewicz and Dhonukshe 2013). By examining the origins of multicellularity in diverse lineages, it can be determined whether commonalities exist that transcend lineage-specific solutions to achieve multicellular organization.…”

Overexpression of CYCD1;2 in activation-tagged Populus tremula x Populus alba results in decreased cell size and altered leaf morphology

“…Cell division (mitosis) is a systematic progression through a series of phases, terminating with chromosome duplication and chromosome segregation into daughter cells after mitosis (Smolarkiewicz and Dhonukshe 2013). For plants in the post-embryonic stage, cell division is restricted to meristems (root and shoot apical meristems, vascular and cork cambiums) and throughout developing leaf blades (reviewed in Gonzalez et al 2012).…”