Biology subjects

Xhelilaj, K.

Publications and source records attributed to Xhelilaj, K..

5 recordsLinked to original sources

bioRxiv2025

An ancient alkalinization factor informs Arabidopsis root development

The power of hydrogen (pH) regulates virtually all cellular activities. In both plants and animals, cell-to-cell variations in pH correlate with key developmental transitions1-5, yet the underlying regulators and associated functions remain elusive. Here, we report that members of the REMORIN (REM) protein family function as inhibitors of the H+-ATPases thereby promoting extracellular pH (pHe) alkalinization. This, in turn, regulates various cell surface processes, including steroid hormone signaling, and coordinates developmental transitions in the Arabidopsis thaliana root. Inhibition of H+-ATPases by REMs represents an evolutionary innovation that predates the origin of the root system itself. This study thus uncovers an ancient alkalinization mechanism co-opted by the root developmental program and infers that pHe patterning may have shaped morphogenesis evolution.

plant biology↗

bioRxiv2025

Salicylic acid-induced alkalinization of the apoplast requires TRANSMEMBRANE KINASE 1 and results in growth attenuation

The phytohormone salicylic acid (SA) has a key role in regulating plant growth and stress response. In the past, most of the growth-related SA functions have been explained by crosstalk with the master growth regulator auxin. By affecting polarity of auxin transporters, SA changes auxin distribution in the root and inhibits growth of the main root and activates lateral root formation. However, only recently there is evidence emerging that SA impacts growth processes independently of nuclear auxin signalling, possessing yet unknown mechanistic functions. Here we show that SA activity depends on TRANSMEMBRANE KINASE 1 (TMK1) resulting in apoplast alkalinization and growth restriction. SA treatment prevents phosphorylation and activation of plasma membrane (PM) H+-ATPases at the cell surface and does not depend on the auxin receptor Auxin Binding Protein 1 (ABP1). We suggest that alkalinization of the apoplast by SA serves as mechanism to balance stress response and growth.

plant biology↗

bioRxiv2024

Photochromic reversion enables long-term tracking of single molecules in living plants.

Single-molecule imaging enables the observation of individual molecules in living cells (DEste et al., 2024; Kusumi et al., 2014; Lelek et al., 2021; Nguyen et al., 2023). In plants, however, the tracking of single molecules is typically limited to a few hundred milliseconds (Bayle et al., 2021; Gronnier et al., 2017; Hosy et al., 2015), precluding the observation of dynamic cellular processes at molecular resolution. Here, we describe photochromic reversion, an imaging modality that enables long-term single-molecule tracking of genetically encoded translational fusions. Using this approach, we achieve minute-long tracking of individual cell-surface receptors and reveal previously inaccessible dynamic spatial arrest events of single plasma membrane proteins. We further developed and benchmarked computational analysis of spatial arrests (CASTA), a machine learning-based tool that automatically detects and analyses spatial, temporal, and diffusional properties of these events, thereby enabling precise nanoscale kinetic measurements. Together, these advances provide a powerful framework for deciphering the principles governing membrane dynamics and function.

cell biology↗

bioRxiv2024

A RALF-Brassinosteroid morpho-signaling circuit regulates Arabidopsis hypocotyl cell shape

Plant cells survey and modulate their cell wall to control their shape and anisotropic growth. Signaling mediated by the plant steroid hormones brassinosteroids (BR) plays a central role in coordinating cell wall status and cell growth, and alterations in the cell wall - BR feedback loop leads to life-threatening defects in tissue and cellular integrity. How the status of the cell wall is relayed to BR signaling remains largely unclear. Increasing evidence shows that RAPID ALKALANIZATION FACTORs (RALFs), a class of secreted peptides, play structural and signaling roles at the cell surface. Here we show that perception of RALF23 promotes the formation and signaling of the main BR receptor complex formed by BRASSINOSTEROID INSENSITIVE 1 (BRI1) and BRI1-BRASSINOSTEROID INSENSITIVE1-BRASSINOSTEROID-ASSOCIATED KINASE 1 (BAK1). The loss of the plasma membrane-localized RALF receptor complex FERONIA (FER)-LORELEI LIKE GPI-anchor protein 1 (LLG1) leads to defects in cell expansion and anisotropy, as well as uncontrolled BRI1-BAK1 complex formation and signaling. RALF23 bioactivity relies on pectin status and its perception induces changes in pectin composition and the activity of pectin-modifying enzymes. Our observations suggest a model in which RALF23 functions as a cell wall-informed signaling cue initiating a feedback loop that solicits BR signaling, modifies the cell wall, and coordinates cell morphogenesis. Highlights-The RALF receptor complex FER-LLG1 regulates cell anisotropic growth -RALF23 promotes BRI1-BAK1 complex formation and signaling -RALF23 functions as a cell wall-informed and wall-modifying signaling cue

plant biology↗

bioRxiv2023

The actin depolymerizing factor StADF2 alters StREM1.3 plasma membrane nanodomains to inhibit the Potato Virus X

The dynamic regulation of the plasma membrane (PM) organization at the nanoscale emerged as a key element shaping the outcome of host-microbe interactions. Protein organization into nanodomains (ND) is often assumed to be linked to the activation of cellular processes. In contrast, we have previously shown that the phosphorylation of the Solanum tuberosum REM1.3 (StREM1.3) N-terminal domain disperses its native ND organization and promotes its inhibitory effect on Potato Virus X (PVX) cell-to-cell movement. Here, we show that the phosphorylation of StREM1.3 modify the chemical environment of numerous residues in its intrinsically-disordered N-terminal domain. We leveraged exploratory screens to identify potential phosphorylation-dependent interactors of StREM1.3. Herewith, we uncovered uncharacterized regulators of PVX cell-to-cell movement, linking StREM1.3 to autophagy, water channels and the actin cytoskeleton. We show that the Solanum tuberosum actin depolymerizing factors 2 (StADF2) alters StREM1.3 NDs and limits PVX cell-to-cell movement in a REMORIN-dependent manner. Mutating a conserved single residue reported to affect ADFs affinity to actin inhibits StADF2 effect on StREM1.3 ND organization and PVX cell-to-cell movement. These observations provide functional links between the organization of plant PM and the actin cytoskeleton and suggests that the alteration of StREM1.3 ND organization promotes plant anti-viral responses. We envision that analogous PM re-organization applies for additional signaling pathways in plants and in other organisms.

cell biology↗