Localization of fluorescently tagged protein to plasmodesmata by correlative light and electron microscopy

Realizing the Full Potential of Advanced Microscopy Approaches for Interrogating Plant-Microbe Interactions

Microscopy has served as a fundamental tool for insight and discovery in plant-microbe interactions for centuries. From classical light and electron microscopy to corresponding specialized methods for sample preparation and cellular contrasting agents, these approaches have become routine components in the toolkit of plant and microbiology scientists alike to visualize, probe and understand the nature of host-microbe relationships. Over the last three decades, three-dimensional perspectives led by the development of electron tomography, and especially, confocal techniques continue to provide remarkable clarity and spatial detail of tissue and cellular phenomena. Confocal and electron microscopy provide novel revelations that are now commonplace in medium and large institutions. However, many other cutting-edge technologies and sample preparation workflows are relatively unexploited yet offer tremendous potential for unprecedented advancement in our understanding of the inner workings of pathogenic, beneficial, and symbiotic plant-microbe interactions. Here, we highlight key applications, benefits, and challenges of contemporary advanced imaging platforms for plant-microbe systems with special emphasis on several recently developed approaches, such as light-sheet, single molecule, super-resolution, and adaptive optics microscopy, as well as ambient and cryo-volume electron microscopy, X-ray microscopy, and cryo-electron tomography. Furthermore, the potential for complementary sample preparation methodologies, such as optical clearing, expansion microscopy, and multiplex imaging, will be reviewed. Our ultimate goal is to stimulate awareness of these powerful cutting-edge technologies and facilitate their appropriate application and adoption to solve important and unresolved biological questions in the field. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Analysis of plasmodesmata permeability using cultured tobacco BY-2 cells entrapped in microfluidic chips

Plasmodesmata are unique channel structures in plants that link the fluid cytoplasm between adjacent cells. Plants have evolved these microchannels to allow trafficking of nutritious substances as well as regulatory factors for intercellular communication. However, tracking the behavior of plasmodesmata in real time is difficult because they are located inside tissues. Hence, a system was constructed to monitor the movement of substances by plasmodesmata using tobacco BY-2 cells, which are linearly organized cells, and a microfluidic device that traps them in place and facilitates observation. After targeting one cell for photobleaching, recovery of the lost H2B-GFP protein was detected within 200 min. No recovery was detected in that time frame by photobleaching the entire cell filaments. This suggested that the recovery of H2B-GFP protein was not due to de novo protein synthesis, but rather to translocation from neighboring cells. The transport of H2B-GFP protein was not observed when sodium chloride, a compound known to cause plasmodesmata closure, was present in the microfluid channel. Thus, using the microfluidic device and BY-2 cells, it was confirmed that the behavior of plasmodesmata could be observed in real time under controllable conditions.

Diversity of Plant Virus Movement Proteins: What Do They Have in Common?

The modern view of the mechanism of intercellular movement of viruses is based largely on data from the study of the tobacco mosaic virus (TMV) 30-kDa movement protein (MP). The discovered properties and abilities of TMV MP, namely, (a) in vitro binding of single-stranded RNA in a non-sequence-specific manner, (b) participation in the intracellular trafficking of genomic RNA to the plasmodesmata (Pd), and (c) localization in Pd and enhancement of Pd permeability, have been used as a reference in the search and analysis of candidate proteins from other plant viruses. Nevertheless, although almost four decades have passed since the introduction of the term “movement protein” into scientific circulation, the mechanism underlying its function remains unclear. It is unclear why, despite the absence of homology, different MPs are able to functionally replace each other in trans-complementation tests. Here, we consider the complexity and contradictions of the approaches for assessment of the ability of plant viral proteins to perform their movement function. We discuss different aspects of the participation of MP and MP/vRNA complexes in intra- and intercellular transport. In addition, we summarize the essential MP properties for their functioning as “conditioners”, creating a favorable environment for viral reproduction.

Plasmodesmata at a glance

Plasmodesmata are cytoplasmic communication channels that are vital for the physiology and development of all plants. They facilitate the intercellular movement of various cargos - ranging from small molecules, such as sugars, ions and other essential nutrients and chemicals, to large complex molecules, such as proteins and different types of RNA species - by bridging neighboring cells across their cell walls. Structurally, an individual channel consists of the cytoplasmic sleeve that is formed between the endoplasmic reticulum and the plasma membrane leaflets. Plasmodesmata are highly versatile channels; they vary in number and structure, and undergo constant adjustments to their permeability in response to many internal and external cues. In this Cell Science at a Glance article and accompanying poster, we provide an overview of plasmodesmata form and function, with highlights on their development and variation, associated components and mobile factors. In addition, we present methodologies that are currently used to study plasmodesmata-mediated intercellular communication.

Knockdown of sodium-calcium exchanger 1 induces epithelial-to-mesenchymal transition in kidney epithelial cells

Mesenchymal-to-epithelial transition (MET) and epithelial-to-mesenchymal transition (EMT) are important processes in kidney development. Failure to undergo MET during development leads to the initiation of Wilms tumor, whereas EMT contributes to the development of renal cell carcinomas (RCC). The role of calcium regulators in governing these processes is becoming evident. We demonstrated earlier that Na⁺/Ca²⁺ exchanger 1 (NCX1), a major calcium exporter in renal epithelial cells, regulates epithelial cell motility. Here, we show for the first time that NCX1 mRNA and protein expression was down-regulated in Wilms tumor and RCC. Knockdown of NCX1 in Madin-Darby canine kidney cells induced fibroblastic morphology, increased intercellular junctional distance, and induced paracellular permeability, loss of apico-basal polarity in 3D cultures, and anchorage-independent growth, accompanied by expression of mesenchymal markers. We also provide evidence that NCX1 interacts with and anchors E-cadherin to the cell surface independent of NCX1 ion transport activity. Consistent with destabilization of E-cadherin, NCX1 knockdown cells showed an increase in β-catenin nuclear localization, enhanced transcriptional activity, and up-regulation of downstream targets of the β-catenin signaling pathway. Taken together, knockdown of NCX1 in Madin-Darby canine kidney cells alters epithelial morphology and characteristics by destabilization of E-cadherin and induction of β-catenin signaling.