Explore the vast range of titles available.

Environmental and physiological situations can challenge the balance between protein synthesis and folding capacity of the endoplasmic reticulum (ER) and cause ER stress, a potentially lethal condition. The unfolded protein response (UPR) restores ER homeostasis or actuates programmed cell death (PCD) when ER stress is unresolved. The cell fate determination mechanisms of the UPR are not well understood, especially in plants. Here, we integrate genetics and ER stress profiling with natural variation and quantitative trait locus analysis of 350 natural accessions of the model species Arabidopsis thaliana . Our analyses implicate a single nucleotide polymorphism to the loss of function of the general PCD regulator BON-ASSOCIATED PROTEIN2 (BAP2) in UPR outcomes. We establish that ER stress-induced BAP2 expression is antagonistically regulated by the UPR master regulator, inositol-requiring enzyme 1 (IRE1), and that BAP2 controls adaptive UPR amplitude in ER stress and ignites pro-death mechanisms in conditions of UPR insufficiency. The unfolded protein response (UPR) is a cellular stress response related to endoplasmic reticulum stress, which is activated upon stress challenging. Here, the authors report that the programmed cell death regulator BAP2 is a plant UPR modulator upstream of the essential UPR master regulator IRE1.

The unfolded protein response (UPR), a highly conserved set of eukaryotic intracellular signaling cascades, controls the homeostasis of the endoplasmic reticulum (ER) in normal physiological growth and situations causing accumulation of potentially toxic levels of misfolded proteins in the ER, a condition known as ER stress. During evolution, eukaryotic lineages have acquired multiple UPR effectors, which have increased the pliability of cytoprotective responses to physiological and environmental stresses. The ER‐associated protein kinase and ribonuclease IRE1 is a UPR effector that is conserved from yeast to metazoans and plants. IRE1 assumes dispensable roles in growth in yeast but it is essential in mammals and plants. The Arabidopsis genome encodes two isoforms of IRE1, IRE1A and IRE1B, whose protein functional domains are conserved across eukaryotes. Here, we describe the identification of a third Arabidopsis IRE1 isoform, IRE1C. This protein lacks the ER lumenal domain that has been implicated in sensing ER stress in the IRE1 isoforms known to date. Through functional analyses, we demonstrate that IRE1C is not essential in growth and stress responses when deleted from the genome singularly or in combination with an IRE1A knockout allele. However, we found that IRE1C exerts an essential role in gametogenesis when IRE1B is also depleted. Our results identify a novel, plant‐specific IRE1 isoform and highlight that at least the control of gametogenesis in Arabidopsis requires an unexpected functional coordination of IRE1C and IRE1B. More broadly, our findings support the existence of a functional form of IRE1 that is required for development despite the remarkable absence of a protein domain that is critical for the function of other known IRE1 isoforms.

Species in the mushroom genus Lepiota can cause fatal mushroom poisonings due to their content of amatoxins such as α-amanitin. Previous studies of the toxin composition of poisonous Lepiota species relied on analytical methods of low sensitivity or resolution. Using liquid chromatography coupled to UV absorbance and mass spectrometry, we analyzed the spectrum of peptide toxins present in six Italian species of Lepiota, including multiple samples of three of them collected in different locations. Field taxonomic identifications were confirmed by sequencing of the internal transcribed spacer (ITS) regions. For comparison, we also analyzed specimens of Amanita phalloides from Italy and California, a specimen of A. virosa from Italy, and a laboratory-grown sample of Galerina marginata. α-Amanitin, β-amanitin, amanin, and amaninamide were detected in all samples of L. brunneoincarnata, and α-amanitin and γ-amanitin were detected in all samples of L. josserandii. Phallotoxins were not detected in either species. No amatoxins or phallotoxins were detected in L. clypeolaria, L. cristata, L. echinacea, or L. magnispora. The Italian and California isolates of A. phalloides had similar profiles of amatoxins and phallotoxins, although the California isolate contained more β-amanitin relative to α-amanitin. Amaninamide was detected only in A. virosa.

Environmental stress demands precise coordination among organelles to maintain cellular homeostasis. In Arabidopsis, high light (HL) exposure triggers chloroplast‐dependent remodeling of mitochondrial and endoplasmic reticulum (ER) morphology specifically in adaxial and abaxial epidermal cells, but not in mesophyll cells. Live‐cell imaging reveals that HL rapidly suppresses mitochondrial motility, followed by fusion‐driven elongation and ER cisternal expansion. Inhibition of photosynthetic, but not mitochondrial, electron transport abolishes these changes, confirming chloroplast activity as the upstream trigger. Pharmacological analyses show that exogenous H2O2 induces mitochondrial elongation, whereas calcium chelation blocks both H2O2‐ and HL‐induced responses, demonstrating that chloroplast‐derived H2O2 activates a Ca2+ flux essential for remodeling. Proteomic and functional studies identify the Ca2+‐binding GTPase MIRO1 as a central integrator of this pathway. MIRO1 overexpression mimics HL‐induced morphodynamics, while mutations disrupting its Ca2+‐binding or acetylation motifs abolish the response, establishing Ca2+‐dependent MIRO1 activity as a prerequisite for remodeling. Together, these findings reveal an epidermis‐specific, light‐responsive network in which chloroplast‐derived H2O2 initiates Ca2+ signaling through MIRO1 to coordinate mitochondrial and ER remodeling—a spatially restricted mechanism of organellar communication and stress adaptation at the plant–environment interface. High light exposure triggers an epidermis‐specific remodeling of mitochondria and ER in Arabidopsis, driven by chloroplast‐derived signals. Live‐cell imaging shows that HL rapidly suppresses mitochondrial motility, followed by fusion‐driven elongation and ER cisternal expansion. MIRO1 emerges as a key mediator, linking chloroplast activity to dynamic interorganellar restructuring at the plant–environment interface.

Doc number: 52 Abstract Background: Many different feedstocks are under consideration for the practical production of biofuels from lignocellulosic materials. The best choice under any particular combination of economic, agronomic, and environmental conditions depends on multiple factors. The use of old fields, restored prairie, or marginal lands to grow biofuel feedstocks offers several potential benefits including minimal agronomic inputs, reduced competition with food production, and high biodiversity. However, a major component of such landscapes is often herbaceous dicotyledonous plants, also known as forbs. The potential and obstacles of using forbs as biofuel feedstocks compared to the more frequently considered grasses and woody plants are poorly understood. Results: The factors that contribute to the yield of fermentable sugars from four representative forbs were studied in comparison with corn stover. The forbs chosen for the study were lamb's quarters (Chenopodium album ), goldenrod (Solidago canadensis ), milkweed (Asclepias syriaca ), and Queen Anne's lace (Daucus carota ). These plants are taxonomically diverse, widely distributed in northern temperate regions including the continental United States, and are weedy but not invasive. All of the forbs had lower total glucose (Glc) content from all sources (cell walls, sucrose, starch, glucosides, and free Glc) compared to corn stover (range 16.2 to 23.0% on a dry weight basis compared to 39.2% for corn stover). When digested with commercial enzyme mixtures after alkaline pretreatment, yields of Glc as a percentage of total Glc were lower for the forbs compared to corn stover. Enzyme inhibition by water-extractable compounds was not a significant contributor to the lower yields. Based on experiments with optimized cocktails of pure glycosyl hydrolases, enzyme imbalance probably accounted for much of the lower yields. Addition of xyloglucanase and α-xylosidase, two enzymes targeting Glc-containing polysaccharides that are more abundant in dicotyledonous plants compared to grasses, enhanced Glc yields from lamb's quarters, but Glc yields were still lower than from corn stover. Conclusion: The potential utilization of forb-rich plant communities as biofuel feedstocks must take into account their lower Glc content compared to grasses such as corn stover. Furthermore, new enzyme mixtures tailored to the different cell wall composition of forbs will have to be developed.

Environmental and physiological situations can challenge the balance between protein synthesis and folding capacity of the endoplasmic reticulum (ER) and cause ER stress, a potentially lethal condition. The unfolded protein response (UPR) restores ER homeostasis or actuates programmed cell death (PCD) when ER stress is unresolved. The cell fate determination mechanisms of the UPR are not well understood, especially in plants. Here, we integrate genetics and ER stress profiling with natural variation and quantitative trait locus analysis of 350 natural accessions of the model species Arabidopsis thaliana. Our analyses implicate a single nucleotide polymorphism to the loss of function of the general PCD regulator BON-ASSOCIATED PROTEIN2 (BAP2) in UPR outcomes. We establish that ER stress-induced BAP2 expression is antagonistically regulated by the UPR master regulator, inositol-requiring enzyme 1 (IRE1), and that BAP2 controls adaptive UPR amplitude in ER stress and ignites pro-death mechanisms in conditions of UPR insufficiency.

The unfolded protein response (UPR), a highly conserved set of eukaryotic intracellular signaling cascades, controls the homeostasis of the endoplasmic reticulum (ER) in normal physiological growth and situations causing accumulation of potentially toxic levels of misfolded proteins in the ER, a condition known as ER stress. During evolution, eukaryotic lineages have acquired multiple UPR effectors, which have increased the pliability of cytoprotective responses to physiological and environmental stresses. The ER-associated protein kinase and ribonuclease IRE1 is a UPR effector that is conserved from yeast to metazoans and plants. IRE1 assumes dispensable roles in growth in yeast but it is essential in mammals and plants. The Arabidopsis genome encodes two isoforms of IRE1, IRE1A and IRE1B, whose protein functional domains are conserved across eukaryotes. Here, we describe the identification of a third Arabidopsis IRE1 isoform, IRE1C. This protein lacks the ER lumenal domain that has been implicated in sensing ER stress in the IRE1 isoforms known to date. Through functional analyses, we demonstrate that IRE1C is not essential in growth and stress responses when deleted from the genome singularly or in combination with an IRE1A knockout allele. However, we found that IRE1C exerts an essential role in gametogenesis when IRE1B is also depleted. Our results identify a novel, plant-specific IRE1 isoform and highlight that at least the control of gametogenesis in Arabidopsis requires an unexpected functional coordination of IRE1C and IRE1B. More broadly, our findings support the existence of a functional form of IRE1 that is required for development despite the remarkable absence of a protein domain that is critical for the function of other known IRE1 isoforms.