Biology subjects

Vidali, L.

Publications and source records attributed to Vidali, L..

8 recordsLinked to original sources

bioRxiv2026

Evolutionary co-option of the ancient protein AMBRA1 in plant photomorphogenesis

Photomorphogenesis, the light-driven developmental program of plants, is repressed in darkness by the CUL4-DDB1-COP1 ubiquitin ligase complex. In animals, AMBRA1 is a substrate receptor for the same CUL4-DDB1 machinery, regulating proteostasis, cell proliferation and autophagy, but its role in plants has remained unknown. Here we show that the moss Physcomitrium patens carries two light-regulated AMBRA1 genes, AMBRA1a and AMBRA1b, whose loss impairs vegetative growth and cell-fate transitions under light and prevents the elongation of gravitropic filaments in darkness, indicating that AMBRA1 is required to repress photomorphogenesis. AMBRA1 localizes to the nucleus under both long-day and dark conditions, and its loss causes widespread transcriptional reprogramming of developmental and metabolic pathways, including repression of photosynthesis-related genes in darkness. These findings identify AMBRA1 as a previously unrecognized nuclear regulator that links light availability to plant growth and as a key repressor of photomorphogenesis.

plant biology↗

bioRxiv2025

A surface morphology-based inference method for the cell wall elasticity profile in tip-growing cells

Plant development and adaptation are highly dependent on cell morphology and growth. High turgor pressure in plants causes stress on the cell wall, followed by cell extension. In tip-growing cells, the localization of vesicles and cytoskeleton components has been well studied. However, there has been a lack of attention to the spatial profile of mechanical properties, specifically the cell wall elasticity. In this study, we introduce a new surface morphology-based method to measure the elasticity of the cell wall in tip-growing cells. Previous work is based on measurements from the wall meridional outline, a technique that cannot track the elastic deformation of the cell wall experimentally. Instead, we developed a way to infer the bulk modulus distribution from the cell surface by triangulating experimental marker points coming from fluorescent labeling. To justify the use of our protocol in tip-growing cells from the moss Physcomitrium patens, we replicated the experimental noise and moss morphology in simulated cells. In practice, we found that a larger triangulation improved robustness against noise, which agreed with our theoretical study. With multiple cell sampling, we determined that 10 cells were sufficient to recover the elasticity distribution with noise, but only when the elastic stretches were high enough. We then created a dimensionless map of inference error to verify a spatial change of P. patens bulk modulus within two folds. This technique will open the field to more comprehensive measurements of cell wall elasticity, providing a key step in understanding tip cell growth and morphogenesis. Author summaryTip-growing cells can be characterized by their fast growth concentrated at the cells apex. Their growth and morphogenesis are tightly regulated processes involving cell wall addition and rearrangement while the cell wall is under stress originating from the cells internal turgor pressure. We start by studying the cell walls elastic properties, one aspect of the cell growth process. We use a method of marker point tracking across the surface of the tip-growing cell to measure the walls elasticity profile. In this work, we present a parameter sensitivity study of this method on synthetic cells and report our results on experimental moss tip-growing cells. Our results suggest that this inference method can reliably measure a cell wall elasticity gradient under combined geometric and mechanical conditions that create elastic strains within 5% at the tip.

plant biology↗

bioRxiv2022

Self-similar tip growth links exocytosis profile with cell wall shape

Exocytosis plays a crucial role in regulating the growth and migration of filamentous tip-growing cells. We present a mathematical framework that infers the spatial profile of exocytosis from the cell morphology in self-similar growing cells that elongate while preserving their apical domain shapes. By applying the framework to cell wall outline data from experiments across walled cell species, we find that while tapered cells have their exocytosis concentrated at the apex, cells with flatter tip shape beyond a threshold require exocytosis to peak in an annulus region away from the apex.

biophysics↗

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↗

bioRxiv2020

Robust survival-based RNAi using in tandem silencing of adenine phosphoribosyltransferase

RNA interference (RNAi) enables flexible and dynamic interrogation of entire gene families or essential genes without the need for exogenous proteins, unlike CRISPR-Cas technology. Unfortunately, isolation of plants undergoing potent gene silencing requires laborious design, visual screening, and physical separation for downstream characterization. Here, we developed a novel APT-based RNAi technology (APTi) in Physcomitrella patens that simultaneously improves upon the multiple limitations of current RNAi techniques. APTi exploits the pro-survival output of transiently silencing the APT gene in the presence of 2-fluoradenine, thereby establishing survival itself as a reporter of RNAi. To maximize silencing efficacy of gene targets we created vectors that facilitate insertion of any gene target sequence in tandem with the APT silencing motif. The APTi approach resulted in a homogenous population of P. patens mutants specific for our gene target, with zero surviving background plants within 8 days. The observed mutants directly corresponded to a maximal 93% reduction of the tested target protein, substantially exceeding previous dsRNA methods. The positive selection nature of APTi represents a fundamental improvement in RNAi technology and will contribute to the growing demand for technologies amenable to high-throughput phenotyping. One-sentence summaryGeneration of dsRNA targeting the APT gene in tandem with a target gene enables positive selection of strongly silencing plants.

plant biology↗

bioRxiv2019

In vivo Interactions between Myosin XI, Vesicles, and Filamentous Actin Are Fast and Transient

The apical actin cytoskeleton and active membrane trafficking machinery are essential in driving polarized cell growth. To better understand the interactions between myosin XI, vesicles, and actin filament in vivo, we performed Fluorescence Recovery After Photobleaching (FRAP) and showed that the dynamics of myosin XIa at the tip are actin-dependent and that approximately half of myosin XI is bound to vesicles in the cell. To obtain single particle information, we used Variable Angle Epifluorescence Microscopy (VAEM) in Physcomitrella patens protoplasts to demonstrate that myosin XIa and VAMP72-labeled vesicles localize in time and space for periods lasting only a few seconds. Using tracking data with Hidden Markov Modeling (HMM), we showed that myosin XIa and VAMP72-labeled vesicles exhibit short runs of actin-dependent directed transport. We also found that the interaction of myosin XI with vesicles is short lived. Together, this bound fraction, fast off-rate, and short run lengths are expected to be critical for the dynamic oscillations observed at the cell apex, and may be vital for the regulation and recycling of the exocytosis machinery; while simultaneously promoting the vesicle focusing and secretion at the tip, necessary for cell wall expansion.

cell biology↗

bioRxiv2019

Myosin XI Interacting with a RabE GTPase Is Required for Polarized Growth

The fundamental eukaryotic process of intracellular trafficking requires the interconnected activity of molecular motors trafficking vesicular cargo within a dynamic cytoskeletal network. However, in plants, few mechanistic details are known about how molecular motors associate with their secretory cargo to support the ubiquitous processes of polarized growth and cell division. A yeast two-hybrid screen of a Physcomitrella patens library identified a RabE GTPase as an interactor of myosin XI and subsequently demonstrated all five RabE members interact with myosin XI. Consistent with a role in polarized transport, we observed RabE at the growing cell apex and at the expanding cell plate during cell division. An in vivo cross-correlation analysis of fluorescently tagged RabE and myosin XI revealed that both species are spatiotemporally coupled, demonstrating their simultaneous involvement in polarized growth. To determine if myosin XI and RabE are directly coupled, we first computationally predicted myosin XI:RabE interface through a homology modeling-directed approach. We identified a structurally conserved residue on myosin XI, V1422, that when mutated abolished RabE binding in the yeast two-hybrid system and resulted in unpolarized plants instead of the characteristic network of filamentous cells when regenerated from single cells. Together, this work demonstrates the requirement of a direct myosin XI:RabE interaction for polarized growth in plants.

cell biology↗

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↗