Cell Cycle Dynamics during Stomatal Development: Window of MUTE Action and Ramification of Its Loss-of-Function on an Uncommitted Precursor.

Plants develop in the absence of cell migration. As such, cell division and differentiation need to be coordinated for functional tissue formation. Cellular valves on the plant epidermis, stomata, are generated through a stereotypical sequence of cell division and differentiation events.

Deceleration of the cell cycle underpins a switch from proliferative to terminal divisions in plant stomatal lineage.

Differentiation of specialized cell types requires precise cell-cycle control. Plant stomata are generated through asymmetric divisions of a stem-cell-like precursor followed by a single symmetric division that creates paired guard cells surrounding a pore. The stomatal-lineage-specific transcription factor MUTE terminates the asymmetric divisions and commits to differentiation.

Shouting out loud: signaling modules in the regulation of stomatal development.

Stomata are small pores on the surface of land plants that facilitate gas exchange for photosynthesis while minimizing water loss. The function of stomata is pivotal for plant growth and survival. Intensive research on the model plant Arabidopsis (Arabidopsis thaliana) has discovered key peptide signaling pathways, transcription factors, and polarity components that together drive proper stomatal development and patterning.

KINESIN-12E regulates metaphase spindle flux and helps control spindle size in Arabidopsis.

The bipolar mitotic spindle is a highly conserved structure among eukaryotes that mediates chromosome alignment and segregation. Spindle assembly and size control are facilitated by force-generating microtubule-dependent motor proteins known as kinesins. In animals, kinesin-12 cooperates with kinesin-5 to produce outward-directed forces necessary for spindle assembly.

Phragmoplast Orienting Kinesin 2 Is a Weak Motor Switching between Processive and Diffusive Modes.

Plant development and morphology relies on the accurate insertion of new cell walls during cytokinesis. However, how a plant cell correctly orients a new wall is poorly understood. Two kinesin class-12 members, phragmoplast orienting kinesin 1 (POK1) and POK2, are involved in the process, but how these molecular machines work is not known.

Dual localized kinesin-12 POK2 plays multiple roles during cell division and interacts with MAP65-3.

Kinesins are versatile nano-machines that utilize variable non-motor domains to tune specific motor microtubule encounters. During plant cytokinesis, the kinesin-12 orthologs, PHRAGMOPLAST ORIENTING KINESIN (POK)1 and POK2, are essential for rapid centrifugal expansion of the cytokinetic apparatus, the phragmoplast, toward a pre-selected cell plate fusion site at the cell cortex. Here, we report on the spatio-temporal localization pattern of POK2, mediated by distinct protein domains.

Putative RopGAPs impact division plane selection and interact with kinesin-12 POK1.

Cell shape is defined by the surrounding cell walls in plants. Thus, spatial control over cell division planes and cell expansion polarity are essential to maintain cell morphology. In eukaryotes, cell polarity and expansion are controlled by Rho GTPase signalling, regulating cytoskeletal reorganization and vesicle trafficking(1).

Mechanisms of plant cell division.

Plant cells are confined by a network of cellulosic walls that imposes rigid control over the selection of division plane orientations, crucial for morphogenesis and genetically regulated. While in animal cells and yeast, the actin cytoskeleton is instrumental in the execution of cytokinesis, in plant cells the microtubule cytoskeleton is taking the lead in spatially controlling and executing cytokinesis by the formation of two unique, plant-specific arrays, the preprophase band (PPB) and the phragmoplast. The formation of microtubule arrays in plant cells is contingent on acentrosomal microtubule nucleation.