Masayoshi Nakamura

Previous studies showed that sub-micromolar concentrations of the microtubule-targeting herbicide propyzamide cause a right-handed helical arrangement of cortical microtubule arrays and left-handed twisting in elongating Arabidopsis epidermal cells. When seedlings were grown in the presence of 1-2 microM propyzamide or 50-100 nM oryzalin, we show that microtubules spent more time in a paused state in which they exhibited little net change in length. The drug treatment also resulted in slower gro

Plant cortical microtubules are mainly nucleated on previously established microtubules, grow at a narrow range of angles to the wall of mother microtubules, and eventually are released from the nucleation sites. These nucleation events are thought to be regulated by gamma-tubulin-containing complexes. We here show that a null mutation of Arabidopsis GCP2, a core subunit of the gamma-tubulin-containing complex, severely impaired the development of male and female gametophytes. However, a missens

The cortical microtubule arrays of higher plants are organized without centrosomes and feature treadmilling polymers that are dynamic at both ends. The control of polymer end stability is fundamental for the assembly and organization of cytoskeletal arrays, yet relatively little is understood about how microtubule minus ends are controlled in acentrosomal microtubule arrays, and no factors have been identified that act at the treadmilling minus ends in higher plants. Here, we identify <i>Arabido

Plant hormones play important roles in plant growth and development and physiology, and in acclimation to environmental changes. The hormone signaling networks are highly complex and interconnected. It is thus important to not only know where the hormones are produced, how they are transported and how and where they are perceived, but also to monitor their distribution quantitatively, ideally in a non-invasive manner. Here we summarize the diverse set of tools available for quantifying and visua

Microtubules in eukaryotic cells are nucleated from ring-shaped complexes that contain γ-tubulin and a family of homologous γ-tubulin complex proteins (GCPs), but the subunit composition of the complexes can vary among fungi, animals and plants. Arabidopsis GCP3-interacting protein 1 (GIP1), a small protein with no homology to the GCP family, interacts with GCP3 in vitro, and is a plant homolog of vertebrate mitotic-spindle organizing protein associated with a ring of γ-tubulin 1 (MOZART1), a re

In higher plants, reorientation of cortical microtubule arrays has been postulated to be of importance for modifying cell growth to adapt to environmental conditions. However, the process of microtubule reorientation is largely unknown. Recent genetic and live cell imaging studies of microtubule dynamics shed light on the regulatory mechanisms of microtubule molecular nucleation and severing apparatuses, which are required for array reorientation in response to blue light signaling. Branching nu

The latent left–right asymmetry (chirality) of vascular plants is best witnessed as a helical elongation of cylindrical organs in climbing plants. Interestingly, helical handedness is usually fixed in given species, suggesting genetic control of chirality. Arabidopsis thaliana, a small mustard plant, normally does not twist but can be mutated to exhibit helical growth in elongating organs. Genetic, molecular and cell biological analyses of these twisting mutants are providing mechanistic insight

Fluorescent probes are powerful tools for visualizing cellular and subcellular structures, their dynamics and cellular molecules in living cells and enable us to monitor cellular processes in a spatiotemporal manner within complex and crowded systems. In addition to popular fluorescent proteins, a wide variety of small-molecule dyes have been synthesized through close association with the interdisciplinary field of chemistry and biology, ranging from those suitable for labeling cellular compartm

Microtubules are severed by katanin at distinct cellular locations to facilitate reorientation or amplification of dynamic microtubule arrays, but katanin targeting mechanisms are poorly understood. Here we show that a centrosomal microtubule-anchoring complex is used to recruit katanin in acentrosomal plant cells. The conserved protein complex of Msd1 (also known as SSX2IP) and Wdr8 is localized at microtubule nucleation sites along the microtubule lattice in interphase Arabidopsis cells. Katan

The seasonal variation in the adrenal cortex cells of bullfrog was studied histologically in order to ellucidate the origination of the summer cell. In frogs, the lipid cells rich in lipid granules and the spherical eosinophilic summer cells are distributed irregularly in the anastomosing cords without making the discrete zonation. The summer cells are numerous in April and July. Especially in April frogs, the cortex is full of hypertrophied summer cells containing the big granules stained with

Plant cell cortical microtubules are located beneath the plasma membrane and direct the location of cellulose synthases during interphase, influencing cell morphology. Microtubule-associated proteins (MAPs) regulate these microtubules in response to growth and environmental stimuli. This review focuses on recent advances in understanding microtubule nucleation mechanisms in plants and the spatiotemporal regulation of cortical arrays via phytohormone signaling. Emphasis is placed on the conserved

Microtubule severing by katanin plays key roles in generating various array patterns of dynamic microtubules, while also responding to developmental and environmental stimuli. Quantitative imaging and molecular genetic analyses have uncovered that dysfunction of microtubule severing in plant cells leads to defects in anisotropic growth, division and other cell processes. Katanin is targeted to several subcellular severing sites. Intersections of two crossing cortical microtubules attract katanin