Biology subjects

Bellandi, A.

Publications and source records attributed to Bellandi, A..

6 recordsLinked to original sources

bioRxiv2026

Plant Acupuncture: a low-cost and open-source device for local mechanical stimulation

Background: Mechanical signals are important regulators of cellular responses in plants. They guide plant development and can activate defense and repair mechanisms. Yet, the molecular mechanisms by which plants perceive, transduce, and interpret mechanical signals are still poorly understood. This is in part due to the lack of methods to apply local, precise and non-damaging mechanical forces to plant cells. Micro-indentation is highly suitable for this purpose, yet available instrumentation is often expensive and difficult to combine with high-resolution microscopy. Results: We designed an open-source and affordable modular indentation device, consisting of 3D printed elements, 3 commercially available piezo motors, and a variety of indentation needles. Due to its modularity, the setup can be readily adapted to meet experimental requirements and works on all microscopes with bespoke adaptors. We show that the setup can be used to explore both rapid and slower touch responses, exemplified by visualizing calcium waves and actin patches induced by touch. We also show that the setup is compatible with various plant species and tissues and can be combined with high-resolution functional imaging. Conclusions: The simple and flexible design of the indentation device presented in this paper ensures that any lab with a 3D printer can build their own setup at low cost and with minimal time investment. The system has a wide range of applications for live plant tissue, making indentation experiments and thereby plant mechanobiology studies, more accessible.

plant biology↗

bioRxiv2026

Live confocal imagining of cellular touch responses upon local quantifiable mechanical stimulation in plant cells

Plant cells grow and differentiate in an ever-changing environment characterized by transient signals and stimuli. The ability of plant cells to perceive, integrate, and dynamically respond to these stimuli underpins a plant adaptation and survival. Among the plethora of complex stimuli plant cells are exposed to, several stimuli have a mechanical component, for example, wind, touch, contact with insects, penetration of pathogens, and even intrinsic mechanical stresses arising during tissue growth. Despite the presence of a load-bearing cell wall that separates cells from the environment and fixes their location within a tissue, plant cells are responsive to mechanical stimuli. However, several questions remain unanswered around how mechanical stimuli are perceived and translated into cellular responses. Here we establish a system enabling application of quantifiable localized mechanical stress while simultaneously capturing cellular responses with high spatio-temporal resolution using confocal imaging. We show that this system enables estimation of locally applied pressure and provides access to the temporal and spatial details of subcellular events in intact living tissues upon touch. We propose that observing these subcellular events at high spatiotemporal resolution and linking their dynamics to the intensity of mechanical stimuli may uncover the molecular mechanisms underlying plant cell responses to touch.

plant biology↗

bioRxiv2025

A molecular glue: LecRKI.9 creates stiff plasma membrane cell wall connections

Water stress challenges plasma membrane - wall attachment. When plants are exposed to strong hyperosmotic stress, water exits the cell leading to plasmolysis, where the plasma membrane detaches partially from the cell wall and reveals discrete and persistent attachment sites in the form of Hechtian strands. Although these structures have been observed in several species for more than a century, the molecular bases behind plasma membrane - wall attachment remains elusive. Through a screen of candidate proteins, we reveal that the overexpression of two lectin receptor-like proteins (LecRK-I.9 and LecTM) increases the density of plasma membrane - wall connections in N. Benthamiana. The extracellular lectin domain of LecRK-I.9 was able to remain in the wall during plasmolysis. Conversely, deletion of the lectin domain in the LecRK-I.9 overexpressor restored the density of Hechtian strands to WT levels. In Arabidopsis, upon hyperosmotic stress, LecRK-I.9 formed largely immobile clusters, whereas lectin-deleted versions of LecRK-I.9 clusters were mobile. Cluster density correlated with predicted tensile stress levels and mechanical reinforcement in the wall before plasmolysis, consistent with a scenario in which attachment of the lectin domain also reflects the wall properties. Last, while overexpressing LecRK-I.9 conferred resistance to low water potential conditions, deletion of the lectin domain in the LecRK-I.9 overexpressor restored a WT response to water stress. Altogether, this demonstrates that the lectin domain of LecRK-I.9 creates persistent plasma membrane - wall attachment sites, with physiological relevance for plant resistance to water stress. SIGNIFICANCE STATEMENTAs observed since the mid-19th century, when placed in hyperosmotic conditions, plant cells undergo plasmolysis and form thin membraneous threads called Hechtian strands. These structures reflect the presence of persistent plasma membrane - cell wall attachment sites. Yet, the molecular components behind these sites are unknown. Through a candidate screen approach, we identify and demonstrate that the lectin domain of a receptor-like kinase provides such molecular glue. We also show that the clustering of the receptor is patterned and correlate with mechanically reinforced cell walls. Conversely, we find that the promotion of attachment increases resistance to water stress. This work revisits an old plant cell biology classic, and opens new avenues of research for plant adaptation to their environment.

plant biology↗

bioRxiv2024

Plasmodesmal closure elicits stress responses

Plant cells are connected to their neighbors via plasmodesmata facilitating the exchange of nutrients and signaling molecules. During immune responses, plasmodesmata close, but how this contributes towards a full immune response is unknown. To investigate this, we developed two transgenic lines with which we could induce plasmodesmal closure independently of immune elicitors, using the over-active CALLOSE SYNTHASE3 allele icals3m and the C-terminus of PDLP1 to drive callose deposition at plasmodesmata. Induction of plasmodesmal closure increased the expression of stress responsive genes, salicylic acid accumulation and resistance to Pseudomonas syringae DC3000. More homogeneous plasmodesmal closure using icals3m also led to the accumulation of starch and sugars, decreased leaf growth, as well as hypersusceptibility to Botrytis cinerea. Based on the profile of responses, we conclude that plasmodesmal closure itself activates stress signaling, raising questions of what signals mediate this response and whether these responses occur in all circumstances when plasmodesmata close.

plant biology↗

bioRxiv2022

The Hyaloperanospora arabidopsidis effector HaRxL77 is hypermobile between cells and manipulates host defence

Multicellular organisms require dynamic communication between cells, tissues and organs to integrate responses to external and internal signals. In plants, cell-to-cell communication relies in part on plasmodesmata, which connect adjacent cells and allow the exchange of signals and resources. Upon infection by pathogens, plants act to isolate infected cells from non-infected cells by closing plasmodesmata but pathogens can suppress this defence and maintain plasmodesmata in an open state. To address the question of what a pathogen might gain from keeping plasmodesmata open, we screened effectors from the biotrophic Arabidopsis pathogen Hyaloperonospora arabidopsidis (Hpa) for the ability to move cell-to-cell via plasmodesmata in plant tissues. We quantified the mobility of cytoplasmic effectors and identified six that were hypermobile, i.e., can move further than expected for a protein of that size. Of these, HaRxL77 indirectly modifies plasmodesmatal permeability to facilitate hypermobility and suppresses the flg22-induced ROS burst, suggesting that cell-to-cell mobility of effectors allows defence manipulation ahead of the infection front. Thus, this study provides novel insights into how Hpa exploits plasmodesmata-mediated intercellular connectivity to promote infection, characterising a poorly explored element of plant-pathogen interaction. Author SummaryDuring infection, pathogens secrete effectors into host cells to manipulate them for their benefit. Plant cells are connected via plasmodesmata, and pathogen effectors can use these connections to reach uninfected cells. We asked what a pathogen might gain by having effectors that can travel between cells and thus screened Arabidopsis downy mildew effectors for this capability. We found downy mildew produces many cell-to-cell mobile effectors, and that some of these can move further than we might expect. One hypermobile effector, HaRxL77, can open plasmodesmata to allow this increased mobility, although how it does this is not clear. HaRxL77 interferes with several host defence mechanisms, suggesting that cell- to-cell mobility allows effectors to perturb host defence ahead of the infection front.

plant biology↗

bioRxiv2019

Chitin perception in plasmodesmata identifies subcellular, context-specific immune signalling in plants

The plasma membrane (PM) that lines plasmodesmata has a distinct protein and lipid composition, underpinning specific regulation of these connections between cells. The plasmodesmal PM can integrate extracellular signals differently from the cellular PM, but it is not known how this specificity is established or how a single stimulus can trigger independent signalling cascades in neighbouring membrane domains. Here we have used the fungal elicitor chitin to investigate signal integration and responses at the plasmodesmal PM. We found that the plasmodesmal PM employs a receptor complex composed of the LysM receptors LYM2 and LYK4 which respectively change their location and interactions in response to chitin. Downstream, signalling is transmitted via a specific phosphorylation signature of an NADPH oxidase and localised callose synthesis that causes plasmodesmata closure. This demonstrates the plasmodesmal PM deploys both plasmodesmata-specific components and differential activation of PM-common components to independently integrate an immune signal.

plant biology↗