Biology subjects

Wisanpitayakorn, P.

Publications and source records attributed to Wisanpitayakorn, P..

3 recordsLinked to original sources

bioRxiv2020

Myosin XI drives polarized growth by vesicle clustering and local enrichment of F-actin in Physcomitrium (Physcomitrella) patens

In tip-growing plant cells, growth results from myosin XI and F-actin mediated deposition of cell wall polysaccharides contained in secretory vesicles. Previous evidence showed that myosin XI anticipates F-actin accumulation at the cells tip, suggesting a mechanism where vesicle clustering via myosin XI promotes F-actin polymerization. To evaluate this model, we used a conditional loss-of-function strategy by generating Physcomitrium (Physcomitrella) patens plants harboring a myosin XI temperature-sensitive allele. We found that loss of myosin XI function alters tip cell morphology, vacuolar homeostasis, and cell viability, but not following F-actin depolymerization. Importantly, our conditional loss-of-function analysis shows that myosin XI clusters and directs vesicles at the tip of the cell, which induces F-actin polymerization, increasing F-actins local concentration. Our findings support the role of myosin XI in vesicle clustering and F-actin organization, necessary for tip growth, and deepen our understanding of additional myosin XI functions.

cell biology↗

bioRxiv2019

Kinesin-2 from C. reinhardtii is an atypically fast and auto-inhibited motor that is activated by heterotrimerization for intraflagellar transport

The construction and function of virtually all cilia require the universally conserved process of Intraflagellar Transport (IFT) [1, 2]. During the atypically fast IFT in the green alga C. reinhardtii, up to ten kinesin-2 motors line up in a tight assembly on the trains [3], provoking the question of how these motors coordinate their action to ensure smooth and fast transport along the flagellum without standing in each others way. Here, we show that the heterodimeric FLA8/10 kinesin-2 alone is responsible for the atypically fast IFT in C. reinhardtii. Notably, in single-molecule studies, FLA8/10 moved at speeds matching those of in vivo IFT [4], but additionally displayed a slow velocity distribution, indicative of auto-inhibition. Addition of the KAP subunit to generate the heterotrimeric FLA8/10/KAP relieved this inhibition, thus providing a mechanistic rationale for heterotrimerization with the KAP subunit in fully activating FLA8/10 for IFT in vivo. Finally, we link fast FLA8/10 and slow KLP11/20 kinesin-2 from C. reinhardtii and C. elegans through a DNA tether to understand the molecular underpinnings of motor coordination during IFT in vivo. For motor pairs from both species, the co-transport velocities very nearly matched the single-molecule velocities, and the complexes both spent roughly 80% of the time with only one of the two motors attached to the microtubule. Thus, irrespective of phylogeny and kinetic properties, kinesin-2 motors prefer to work alone without sacrificing efficiency. Our findings thus offer a simple mechanism for how efficient IFT is achieved across diverse organisms despite being carried out by motors with different properties.

biophysics↗

bioRxiv2018

Measurement of the Persistence Length of Cytoskeletal Filaments using Curvature Distributions

Cytoskeletal filaments such as microtubules and actin filaments play important roles in the mechanical integrity of cells and the ability of cells to respond to their environment. Measuring the mechanical properties of cytoskeletal structures is crucial for gaining insight into intracellular mechanical stresses and their role in regulating cellular processes. One of the ways to characterize these mechanical properties is by measuring their persistence length, the average length over which filaments stay straight. There are several approaches in the literature for measuring filament deformations, including Fourier analysis of images obtained using fluorescence microscopy. Here, we show how curvature distributions can be used as an alternative tool to quantify bio-filament deformations, and investigate how the apparent stiffness of filaments depends on the resolution and noise of the imaging system. We present analytical calculations of the scaling curvature distributions as a function of filament discretization, and test our predictions by comparing Monte Carlo simulations to results from existing techniques. We also apply our approach to microtubules and actin filaments obtained from in vitro gliding assay experiments with high densities of non-functional motors, and calculate the persistence length of these filaments. The presented curvature analysis is significantly more accurate compared to existing approaches for small data sets, and can be readily applied to both in vitro or in vivo filament data through the use of an ImageJ plugin we provide.

biophysics↗