Biology subjects

Ejike, J. O.

Publications and source records attributed to Ejike, J. O..

3 recordsLinked to original sources

bioRxiv2024

Identification of nuclear pore proteins at plasmodesmata

Plasmodesmata (PD) mediate intercellular exchange of small molecules, RNAs and proteins between plant cells with an apparent exclusion limit for passive non-specific transport, and transport of specific cargo mediated by mediators. PD and nuclear pore complexes (NPC) are nanometer sized micropores with strikingly similar properties. Cargo translocation through NPC is mediated by phase separating FG-nucleoporins (FG-NUP). Here, bioinformatics, proteomics and fluorescence imaging identified FG-NUPs at PD. Transient expression of GFP fusions at low and intermediate expression levels supported dual localization of 12 NUPs to NPC and PD. Structured illumination microscopy detected the transmembrane anchor NUP CPR5 close to orifices of PD. cpr5 mutants showed reduced intercellular short-root (SHR) transport. However, transport defects cannot be excluded due to indirect effects in the mutants. Identification of FG-NUPs at PD is consistent with the recruitment of NUPs to form a PD pore gating complex consistent with phase separation domains as diffusion barriers at PD. Further analyses will be required to determine whether NUPs are bona fide PD components, or accumulate at PD in certain conditions, or may serve intermediate NPC storage.

cell biology↗

bioRxiv2023

A monochromatically excitable green-red dual-fluorophore fusion incorporating a new large Stokes shift fluorescent protein

Genetically encoded sensors enable quantitative imaging of analytes in live cells. State-of-the-art sensors are commonly constructed by combining ligand-binding domains with one or more sensitized fluorescent protein (FP) domains. Sensors based on a single FP are susceptible to artifacts caused by differing expression levels or sensor distribution in vivo. Hence, our lab developed dual-FP Matryoshka technology introduced by a single cassette that contains a stable large Stokes shift (LSS) reference FP nested within a reporter FP (cpEGFP), allowing simple construction of intensiometric sensors with the capacity for ratiometric quantification. The first-generation Green-Orange (GO) Matryoshka cassette established proof of concept but required custom optical setups to maximize achievable dynamic range. Here, we present a genetically encoded calcium sensor that employs optimized second-generation Green-Apple (GA) Matryoshka technology that incorporates a newly designed red LSSmApple fluorophore. LSSmApple provides improved excitation spectrum overlap with cpEGFP, allowing for monochromatic co-excitation with blue light. The exceptionally large Stokes shift of LSSmApple results in improved emission spectrum separation from cpEGFP, which minimizes fluorophore bleed-through and facilitates imaging using standard dichroics and red fluorescent protein (RFP) emission filters. We developed an image analysis pipeline for yeast (Saccharomyces cerevisiae) timelapse imaging that utilizes LSSmApple to segment and track cells for high-throughput quantitative analysis. In summary, we engineered a new fluorescent protein, constructed a genetically encoded calcium indicator (GA-MatryoshCaMP6s), and performed calcium imaging in yeast as a demonstration.

bioengineering↗

bioRxiv2022

A high confidence Physcomitrium patens plasmodesmata proteome by iterative scoring and validation reveals diversification of cell wall proteins during evolution

Cells of multicellular organisms exchange nutrients, building blocks and information. In animals, this happens via gap junctions, in plants via plasmodesmata (PD). PD have striking properties, translocating a large range of molecules from ions, to metabolites, RNA and proteins up to 40 kDa. PD are hard to characterize due to being deeply embedded into cell walls and the presence of several membranes. While previous studies of protein composition of PD from angiosperms identified large lists of proteins, few were validated. Here, we developed a PD scoring approach in conjunction with systematic localization on a large scale to define a high-confidence PD proteome of Physcomitrium patens. This high confidence PD proteome comprises nearly 300 proteins, which together with the bona fide PD proteins from literature, are made available in the public PDDB database. Conservation of localization across plant species strengthens the reliability of plant PD proteomes and provides a basis for exploring the evolution of this important organelle. In particular, the P. patens PD proteome was highly enriched in cell wall modifying proteins. Callose-degrading glycolyl hydrolase family 17 (GHL17) proteins are presented as an abundant PD protein family with representatives across an evolutionary scale. Exclusively members of the alpha-clade of the GHL17 family are shown to be PD localized and their orthologs occur only in plant species which have developed PD. Members of the EXORDIUM-family and xyloglucan transglycosylases are additional cell-wall located proteins highly abundant in the P. patens PD proteome also showing evolutionary diversification of PD localized family members from other clade members.

plant biology↗