Biology subjects

Grech-Baran, M.

Publications and source records attributed to Grech-Baran, M..

6 recordsLinked to original sources

bioRxiv2026

Annexin 5 is a key player in orchestrating the pollen sequestrome

Like dry seeds, mature pollen grains store a large reservoir of RNA species that enables rapid activation and germination under favorable conditions. The molecular mechanisms governing the accumulation of these RNA reservoirs remain poorly understood. Here, we show that the Arabidopsis pollen-specific protein annexin 5 (ANN5) localizes to the nucleolus and exerts dose-dependent control over ribosome biogenesis, as evidenced by altered steady-state rRNA levels in mature pollen. Ectopic expression of ANN5 also induced the accumulation of translationally repressed RNA in plant somatic tissues. Mechanistically, ANN5 interacts with histone deacetylase 2B (HD2B) and nucleolin (NUC1), which are known epigenetic modulators of ribosome biogenesis. In metabolically active cells, ANN5 associates with ribosomal and ribosome-associated proteins, suggesting it modulates the regulatory landscape of translation. We propose that the primary physiological role of ANN5 is to coordinate the formation and subsequent availability of RNA reserves during pollen maturation and activation.

cell biology↗

bioRxiv2025

Dynamic Rysto receptor remodeling controls its ability to confer extreme resistance

Plant nucleotide-binding leucine-rich repeat receptors (NLRs) mediate effector-triggered immunity (ETI), often accompanied by a hypersensitive response (HR). Conversely, extreme resistance (ER) provides exceptionally rapid and effective antiviral protection without visible cell death, yet the molecular and physiological mechanisms underlying ER remain poorly defined. The TIR-NLR receptor Rysto recognizes the coat protein (CP) of potato virus Y (PVY) and can trigger either ER or HR depending on the context. Here, we demonstrate that the efficacy of Rysto-mediated ER relies on the orchestration of various defense mechanisms. These involve transcriptional priming, and spatial redistribution of the receptor and a subset of chaperones. Rysto-expressing lines exhibit a preactivated immune state, including increased expression of genes encoding glycine-rich proteins associated with the cell wall interface and thickness. Upon PVY infection, Rysto plants undergo rapid transcriptome reprogramming, including redox- and defense-related pathways. At the protein level, Rysto initially forms a pre-active complex with Hsp70 and CP-interacting cochaperonins (CPIPs) which is remodeled upon PVY CP binding. PVY CP competes for Hsp70, enabling Rysto to oligomerize into an active resistosome. This process is further accompanied by relocalization of a subpool of the receptor toward an interface of plasma membrane, cell wall. Our research reveals a chaperone-mediated activation mechanism and spatial immune repositioning that differentiate ER responses from traditional HR, offering a detailed system for achieving durable antiviral resistance in plants.

plant biology↗

bioRxiv2025

Structural basis for heat tolerance in plant NLR immune receptors.

Nucleotide-binding leucine-rich repeat (NLR) immune receptors sense pathogen molecules and oligomerize, initiating defense signaling. Some NLRs function poorly at elevated temperatures for unknown reasons. We show that temperature-sensitive NLRs retain ligand binding at elevated temperatures but are impaired in oligomerization. We identify key residues involved in temperature resilience. Structural modeling reveals stabilizing intramolecular interactions of the NB-ARC domain with surface residues of the adjacent leucine-rich repeat (LRR) that preserve receptor integrity and functionality under heat stress. These insights enable in silico classification of NLRs as temperature-sensitive or -tolerant and underpin design of temperature tolerant variants of temperature sensitive NLRs. These findings provide a mechanistic basis for temperature sensitivity in plant immune receptors and enable engineering of temperature-tolerant disease resistance in crops.

plant biology↗

bioRxiv2025

The NLR immune receptor Roq1 recognizes the Pseudomonas syringae HopAG1 effector via its Nudix domain

O_LIPlant nucleotide-binding leucine-rich repeat receptors (NLRs) sense directly or indirectly effectors - proteins employed by pathogens during infection. While indirect recognition can be initiated by unrelated effectors targeting the same cellular component, direct recognition is restricted by conformational constraints of the pathogen protein and corresponding receptor. C_LIO_LIRecognition of XopQ (Roq1) receptor confers resistance to bacteria expressing members of the highly conserved effector family comprising XopQ/HopQ1/RipB. The structure of the activated Roq1 was solved previously, revealing that LRR and C-JID domains of Roq1 are involved in XopQ binding. C_LIO_LIIn this study, we found that Roq1 detects HopAG1, a member of a structurally different effector family. Presence of HopAG1 in Pseudomonas syringae reduced bacterial growth and symptoms development in wild-type but not in roq1 Nicotiana benthamiana plants. Moreover, HopAG1 co-immunoprecipitated with Roq1 indicating that both proteins associate. Based on deletion and structural analyses, we postulate that this interaction occurs via the Nudix domain of HopAG1 that binds to a similar receptor interface like XopQ. C_LIO_LINudix fold is predicted in multiple pathogen effectors suggesting that Roq1 may recognize effector families other than XopQ and HopAG1. Accordingly, it is also conceivable that other TNLs may detect a broader range of effector families than supposed. C_LI

plant biology↗

bioRxiv2021

The immune Rysto receptor recognizes a broadly conserved feature of potyviral coat proteins

Potyviruses are the largest group of plant RNA viruses, causing significant losses in many crops. Among them, potato virus Y (PVY) is particularly important, and enhances the severity of infections by other viruses. The Rysto gene confers PVY resistance and encodes a TIR-NLR intracellular immune receptors that recognizes PVY coat protein (CP). To define a minimal CP fragment sensed by Rysto, we created a series of truncated CP variants and expressed these CP derivatives in Rysto transgenic plants. Deletions that affect the 149 amino acid CP core region lose the ability to trigger Rysto-dependent defence activation. Furthermore, point mutations in the amino acid residues Ser126, Arg157, and Asp201 of the highly conserved RNA-binding pocket of potyviral CP, reduce or abolish Rysto-dependent responses, demonstrating that appropriate folding of the CP core is required for Rysto-mediated recognition. Consistent with these data, we found Rysto recognises CPs of various viruses that share a similar core region, but not those lacking it. Finally, we demonstrated that Rysto provides immunity to plum pox virus and turnip mosaic virus, demonstrating its wide range of applications in disease-resistant crop engineering. In parallel, we showed that CP triggered Rysto activation is SAG101- but not PAD4- or SA-level dependent. Our findings shed new light on how R proteins can detect viruses by sensing highly conserved structural patterns.

plant biology↗

bioRxiv2018

Extreme resistance to Potato Virus Y in potato carrying the Rysto gene is mediated by a TIR-NLR immune receptor

Potato virus Y (PVY) is a major potato pathogen that causes annual losses of billions of dollars. Control of its transmission requires extensive use of environmentally damaging insecticides. Rysto confers extreme resistance (ER) to PVY and is a valuable trait in resistance breeding programs. We isolated Rysto using Resistance gene enrichment sequencing (RenSeq) and PacBio SMRT (Pacific Biosciences Single-Molecule Real Time Sequencing). Rysto encodes a nucleotide binding-leucine rich repeat (NLR) protein with an N-terminal TIR domain, and is sufficient for PVY perception and extreme resistance in transgenic potato plants. We investigated the requirements for Rysto-dependent extreme resistance, and showed that Rysto function is temperature-independent and requires EDS1 and NRG1 proteins. Rysto may prove valuable for creating PVY-resistant cultivars of potato and other Solanaceae crops.

plant biology↗