Dolata, A. | Search bioRxiv

bioRxiv2026

A single-cell transcriptome atlas of the barley root apical meristem uncovers conserved and divergent roles of HvWOX5

Single-cell approaches have transformed plant developmental biology; however, cell-type-resolved resources for cereals remain limited. Here, we present a single-cell transcriptome atlas of the barley root apical meristem (RAM), which resolves 24 transcriptionally distinct cell populations. We assigned major root cell identities by integrating marker gene validation using Hybridization Chain Reaction (HCR) RNA fluorescence in situ hybridization and spatial transcriptomics with cross-species comparisons of published root atlases. Pseudotime analysis reconstructed developmental trajectories from the quiescent center to differentiating tissues, supporting the spatial and developmental organization of the atlas. We further demonstrated the utility of this resource by identifying HvWOX5 expression in the quiescent center and metaxylem and showing that HvWOX5 loss-of-function mutants displayed reduced root and meristem lengths, altered stem cell niche homeostasis, and disrupted metaxylem organization. Taken together, this atlas provides a framework for dissecting barley root development and identifies HvWOX5 as a key regulator of RAM organization and metaxylem patterning.

Plant Biology↗

bioRxiv2023

Phase separation and molecular ordering of the prion-like domain of the thermosensory protein EARLY FLOWERING 3

Liquid-liquid phase separation (LLPS) is an important mechanism enabling the dynamic compartmentalisation of macromolecules, including complex polymers such as proteins and nucleic acids, and occurs as a function of the physicochemical environment. In the model plant, Arabidopsis thaliana, LLPS by the protein EARLY FLOWERING3 (ELF3) occurs in a temperature sensitive manner and controls thermoresponsive growth. ELF3 contains a largely unstructured prion-like domain (PrLD) that acts as a driver of LLPS in vivo and in vitro. The PrLD contains a poly-glutamine (polyQ) tract, whose length varies across natural Arabidopsis accessions. Here, we use a combination of biochemical, biophysical and structural techniques to investigate the dilute and condensed phases of the ELF3 PrLD with varying polyQ lengths. We demonstrate that the dilute phase of the ELF3 PrLD forms a monodisperse higher order oligomer that does not depend on the presence of the polyQ sequence. This species undergoes LLPS in a pH and temperature-sensitive manner and the polyQ region of the protein tunes the initial stages of phase separation. The liquid phase rapidly undergoes aging and forms a hydrogel as shown by fluorescence and atomic force microscopies. Furthermore, we demonstrate that the hydrogel assumes a semi-ordered structure as determined by small angle X-ray scattering, electron microscopy and X-ray diffraction. These experiments demonstrate a rich structural landscape for a PrLD protein and provide a framework to describe the structural and biophysical properties of biomolecular condensates.

biophysics↗