Biology subjects

Faiss, N.

Publications and source records attributed to Faiss, N..

4 recordsLinked to original sources

bioRxiv2026

TALE-independent transcriptional activation of the rice executor gene Xa23 is regulated via histone acetylation during zygote development

Transcription activator-like effectors (TALEs) from Xanthomonas activate transcription of executor (E) genes in host plants, leading to cell death and thereby restricting proliferation of biotrophic pathogens. Because E gene transcripts had only been detected upon activation by cognate Xanthomonas TALEs, E genes were thought to function exclusively in plant immunity. Here, we detect TALE-independent transcription of the rice E gene Xa23 in zygotes 4-6 hours after gamete fusion. Histone deacetylase inhibition induces Xa23 transcription in unfertilized egg cells, implicating histone acetylation in Xa23 regulation. We identified potential cis-regulatory elements and transcription start sites associated with native Xa23 transcription during zygote development. Together, our findings suggest that Xa23 is a developmentally regulated gene with a native role during early zygote development. This supports a previously proposed model in which E genes have native functions in development, while fortuitous upstream polymorphisms can create TALE-binding sites that convert them into immune executors.

plant biology↗

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↗

bioRxiv2024

NUDIX Hydrolases Target Specific Inositol Pyrophosphates and Regulate Phosphate and Iron Homeostasis, and the Expression of Defense Genes in Arabidopsis

Inositol pyrophosphates (PP-InsPs) are important signaling molecules that regulate diverse cellular processes in eukaryotes, including energy homeostasis, phosphate (Pi) signaling, and phytohormone perception. Yet, in plants, the enzymes responsible for their turnover remain largely unknown. Using a non-hydrolysable PP-InsP analog in a pull-down approach, we identified a family of Arabidopsis NUDIX hydrolases (NUDTs) that group into two closely related subclades. Through in vitro assays, heterologous expression systems, and higher-order gene-edited mutants, we explored the substrate specificities and physiological roles of these hydrolases. Using a combination of strong anion exchange (SAX)-HPLC, PAGE, and capillary electrophoresis electrospray ionization mass spectrometry (CE-ESI-MS), we found that their PP-InsP pyrophosphatase activity is enantiomer-selective and Mg2+-dependent. Specifically, subclade I NUDTs preferentially hydrolyze 4-InsP7, while subclade II NUDTs target 3-InsP7, with minor activity against other PP-InsPs, including 5-InsP7. In higher-order mutants of subclade II NUDTs, we observed defects in both Pi and iron homeostasis, accompanied by increased levels of 1/3-InsP7 and 5-InsP7, with a markedly larger increase in 1/3-InsP7. Ectopic expression of NUDTs from both subclades induced local Pi starvation responses (PSRs), while RNA-seq analysis comparing wildtype (WT) and subclade II nudt12/13/16 loss-of-function plants indicates additional PSR-independent roles, potentially involving 1/3-InsP7 in the regulation of plant defense. Consistently, nudt12/13/16 mutants displayed enhanced resistance to Pseudomonas syringae infection, indicating a role in bacterial pathogen susceptibility. Expanding beyond subclade II NUDTs, we demonstrated susceptibility of the 3PP-position of PP-InsPs to enzymatic activities unrelated to NUDTs, and found that such activities are conserved across plants and humans. Additionally, we found that NUDT effectors from pathogenic ascomycete fungi exhibit a substrate specificity similar to subclade I NUDTs. Collectively, our findings reveal new roles for NUDTs in PP-InsP signaling, plant nutrient and immune responses, and highlight a cross-kingdom conservation of PP-InsP-metabolizing enzymes.

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↗