Biology subjects

Brandizzi, F.

Publications and source records attributed to Brandizzi, F..

7 recordsLinked to original sources

bioRxiv2025

IRE1 Regulates TOR Signaling via RIDD of RAPTOR1b to Coordinate Growth and Stress Adaptation

Plant growth and stress resilience depend on integrating diverse signals into coordinated cellular responses. The endoplasmic reticulum (ER) stress sensor IRE1 maintains ER homeostasis and modulates Target of Rapamycin (TOR) signaling. Here, we reveal that TOR misregulation in an ire1ab mutant reduces sensitivity to the stress hormone abscisic acid (ABA), mediated by TOR-dependent phosphorylation of the ABA receptor PYL1. Further, we show that IRE1s endonuclease activity is required for TOR regulation, acting independently of the canonical IRE1/bZIP60 unfolded protein response. Instead, it occurs via Regulated IRE1- Dependent Decay (RIDD) of specific transcripts. We identify RAPTOR1b as a direct RIDD target, establishing a mechanistic link between ER stress sensing and TOR signaling. RIDD- mediated degradation of RAPTOR1b mRNA is required for appropriate ABA responses and stress adaptation. These findings uncover a noncanonical IRE1-TOR signaling axis that fine- tunes growth and stress responses through selective mRNA decay.

plant biology↗

bioRxiv2025

The MAP kinase scaffold MORG1 shapes cell death in unresolved ER stress in Arabidopsis

Governed by the unfolded protein response (UPR), the ability to counteract endoplasmic reticulum (ER) stress is critical for maintaining cellular homeostasis under adverse conditions. Unresolved ER stress leads to cell death through mechanisms that are yet not completely known. To identify key UPR effectors involved in unresolved ER stress, we performed an ethyl methanesulfonate (EMS) suppressor screen on the Arabidopsis bzip28/60 mutant, which is impaired in activating cytoprotective UPR pathways. This screen identified MAP kinase organizer 1 (MORG1), a conserved MAP kinase scaffold protein, as a previously uncharacterized regulator of ER stress tolerance. The coffin1 mutant, which carries a mutation in MORG1, exhibited enhanced resilience to ER stress by partially restoring UPR gene expression and promoting growth under stress conditions. Mechanistically, we found that MORG1 modulates MPK6-dependent phosphorylation of the stress-responsive transcription factor WRKY8. Loss of WRKY8 phenocopied the coffin1 mutant, highlighting WRKY8s role as a key repressor in the UPR. Together, these findings reveal a MORG1-MPK6-WRKY8 signaling axis that fine-tunes UPR gene expression, providing new insights into ER stress regulation and strategies for improving stress tolerance in multicellular eukaryotes.

plant biology↗

bioRxiv2025

Phosphorus Availability Modulates Flowering Time Through Subcellular Reprogramming of bGLU25 and GRP7 in Flowering Plants

The transition from vegetative to reproductive growth is vital for plant fitness and crop yield and is strongly influenced by nutrient availability. While nitrogen deficiency accelerates flowering, phosphorus (P) limitation delays it. However, the molecular basis for how P availability regulates flowering time remains unclear. Here, through genome-wide association mapping in Arabidopsis, we uncover genetic variation in {beta}-GLUCOSIDASE 25 (bGLU25) that modulates flowering under P-limited conditions. In P-sufficient environments, bGLU25 localizes to the endoplasmic reticulum. Under P limitation, however, bGLU25 translocates to the cytosol, a process mediated by P-regulated SERINE CARBOXY PEPTIDASE 50 (SCP50). In the cytosol, bGLU25 binds to JACALIN-LECTIN LIKE1 (AtJAC1), preventing the nuclear translocation of the Flowering Locus C (FLC) regulator GLYCINE-RICH RNA-BINDING PROTEIN 7 (GRP7). This cytosolic sequestration of GRP7 under P-deprivation elevates FLC expression, delaying flowering. Moreover, in the monocot rice, the homologs of bGLU25 also modulate flowering responses to P availability, indicating a conserved role for bGLU25 across flowering plants. Our findings provide a molecular framework for breeding strategies aimed at optimizing flowering time in response to P levels.

plant biology↗

bioRxiv2022

Characterisation of organised smooth endoplasmic reticulum suggests a route towards synthetic compartmentalisation

Engineering of subcellular compartmentalisation is one of synthetic biologys key challenges. Among different approaches, de novo construction of a synthetic compartment is the most coveted but also most difficult option. Restructuring the endoplasmic reticulum (ER), via the introduction of recombinant oligomerising ER-membrane resident proteins, is an alternative starting point for building a new compartment. The presence of such proteins leads to a massive expansion of the ER and the formation of organised smooth endoplasmic reticulum (OSER), a large membranous compartment. However, OSER is poorly characterised and our understanding of its effect on the underlying biology of the plant is limited. Here we characterise a range of OSER compartments and show how the structure of the inducing polyprotein constructs affect the final compartment morphology, with the cytosolic-facing antiparallel oligomerisation domain demonstrated to be an essential component to trigger OSER formation. We show that while OSER retains a connection to the ER, a diffusional barrier exists to both the ER and the cytosol. Using high-resolution quantitative image analysis, we also show that the presence of this large compartment does not disrupt the rest of the ER network. Moreover, transgenic Arabidopsis constitutively expressing the compartment-forming polyproteins grew and developed normally. These properties collectively suggest that OSER could be developed as a plant synthetic biology tool for compartmentalisation, combining the benefits of several existing strategies. Only a single protein construct is necessary to induce its formation, and the compartment retains a delimiting membrane and a diffusional barrier to the rest of the cell.

plant biology↗

bioRxiv2021

Disruption of Brachypodium Lichenase Alters Metabolism of Mixed-linkage Glucan and Starch

Mixed-linkage glucan (MLG), which is widely distributed in grasses, is a polysaccharide highly abundant in cell walls of grass endosperm and young vegetative tissues. Lichenases are enzymes that hydrolyze MLG first identified in MLG-rich lichens. In this study, we identify a gene encoding a lichenase we name Brachypodium distachyon LICHENASE 1 (BdLCH1), which is highly expressed in the endosperm of germinating seeds and coleoptiles and at lower amounts in mature shoots. RNA in situ hybridization showed that BdLCH1 is primarily expressed in chlorenchyma cells of mature leaves and internodes. Disruption of BdLCH1 resulted in an eight-fold increase in MLG content in senesced leaves. Consistent with the in situ hybridization data, immunolocalization results showed that MLG was not removed in chlorenchyma cells of lch1 mutants as it was in wild type and implicate the BdLCH1 enzyme in removing MLG in chlorenchyma cells in mature vegetative tissues. We also show that MLG accumulation in lch1 mutants was resistant to dark induced degradation, and eight-week-old lch1 plants showed a faster rate of starch breakdown than wild type in darkness. Our results suggest a role for BdLCH1 in modifying the cell wall to support highly metabolically active cells.

plant biology↗

bioRxiv2020

Evolution of a plant gene cluster in Solanaceae and emergence of metabolic diversity

Plants produce phylogenetically and spatially restricted, as well as structurally diverse specialized metabolites via multistep metabolic pathways. Hallmarks of specialized metabolic evolution include enzymatic promiscuity, recruitment of primary metabolic enzymes and genomic clustering of pathway genes. Solanaceae plant glandular trichomes produce defensive acylsugars, with aliphatic sidechains that vary in length across the family. We describe a tomato gene cluster on chromosome 7 involved in medium chain acylsugar accumulation due to trichome specific acyl-CoA synthetase and enoyl-CoA hydratase genes. This cluster co-localizes with a tomato steroidal alkaloid gene cluster forming a supercluster, and is syntenic to a chromosome 12 region containing another acylsugar pathway gene. We reconstructed the evolutionary events leading to emergence of this gene cluster and found that its phylogenetic distribution correlates with medium chain acylsugar accumulation across the Solanaceae. This work reveals dynamics behind emergence of novel enzymes from primary metabolism, gene cluster evolution and cell-type specific metabolite diversity.

plant biology↗

bioRxiv2019

Plant growth regulators interact with elevated temperature to alter heat stress signaling via the Unfolded Protein Response

Plants are increasingly exposed to high temperatures, which can cause accumulation of unfolded protein in the endoplasmic reticulum (ER). This condition, known as ER stress, evokes the unfolded protein response (UPR), a cytoprotective signaling pathway. One important branch of the UPR is regulated by splicing of bZIP60 mRNA by the IRE1 stress sensor. There is increasing evidence that commercial plant growth regulators may protect against abiotic stressors including heat stress and drought, but there is very little mechanistic information about these effects or about the regulatory pathways involved. We evaluated evidence in the B73 Zea mays inbred for differences in the activity of the UPR between permissive and elevated temperature in conjunction with plant growth regulator application. Treatment with elevated temperature and plant growth regulators increased UPR activation, as assessed by an increase in splicing of the mRNA of the IRE1 target bZIP60 following paclobutrazol treatment. We propose that plant growth regulator treatment induces bZIP60 mRNA splicing which primes plants for rapid adaptive response to subsequent endoplasmic reticulum-stress inducing conditions.

plant biology↗