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Land plants need precise thermosensors to timely establish molecular defenses in anticipation of upcoming noxious heat waves. The plasma membrane-embedded cyclic nucleotide-gated Ca²⁺ channels (CNGCs) can translate mild variations of membrane fluidity into an effective heat shock response, leading to the accumulation of heat shock proteins (HSP) that prevent heat damages in labile proteins and membranes. Here, we deleted by targeted mutagenesis the CNGCd gene in two Physcomitrella patens transgenic moss lines containing either the heat-inducible HSP-GUS reporter cassette or the constitutive UBI-Aequorin cassette. The stable CNGCd knockout mutation caused a hyperthermosensitive moss phenotype, in which the heatinduced entry of apoplastic Ca²⁺ and the cytosolic accumulation of GUS were triggered at lower temperatures than in wild type. The combined effects of an artificial membrane fluidizer and elevated temperatures suggested that the gene products of CNGCd and CNGCb are paralogous subunits of Ca²⁺ channels acting as a sensitive proteolipid thermocouple. Depending on the rate of temperature increase, the duration and intensity of the heat priming preconditions, terrestrial plants may thus acquire an array of HSP-based thermotolerance mechanisms against upcoming, otherwise lethal, extreme heat waves.

Land plants are prone to strong thermal variations and must therefore sense early moderate temperature increments to induce appropriate cellular defenses, such as molecular chaperones, in anticipation of upcoming noxious temperatures. To investigate how plants perceive mild changes in ambient temperature, we monitored in recombinant lines of the moss Physcomitrella patens the activation of a heat-inducible promoter, the integrity of a thermolabile enzyme, and the fluctuations of cytoplasmic calcium. Mild temperature increments, or isothermal treatments with membrane fluidizers or Hsp90 inhibitors, induced a heat shock response (HSR) that critically depended on a preceding Ca²⁺ transient through the plasma membrane. Electrophysiological experiments revealed the presence of a Ca²⁺-permeable channel in the plasma membrane that is transiently activated by mild temperature increments or chemical perturbations of membrane fluidity. The amplitude of the Ca²⁺ influx during the first minutes of a temperature stress modulated the intensity of the HSR, and Ca²⁺ channel blockers prevented HSR and the onset of thermotolerance. Our data suggest that early sensing of mild temperature increments occurs at the plasma membrane of plant cells independently from cytosolic protein unfolding. The heat signal is translated into an effective HSR by way of a specific membrane-regulated Ca²⁺ influx, leading to thermotolerance.

Climate change is intensifying ecological instability in agricultural ecosystems, altering pest distribution and increasing the risk of fungal contamination and mycotoxin accumulation in crops. Among emerging threats, the invasive brown marmorated stink bug Halyomorpha halys has rapidly expanded across Europe, including Croatia. The species is polyphagous, and in the ripening of most plant crops, it accounts for a significant population and causes extensive plant damage. This study investigates the capacity of H. halys to disseminate mycotoxigenic fungi, with an emphasis on aflatoxin B1 (AFB1) and ochratoxin A (OTA) producers. One hundred adult H. halys individuals were collected from maize ears in Osijek, Croatia, in August 2023. Fungal propagules washed from their surfaces were inoculated on PDA and MEA media. A total of 212 pure fungal cultures were obtained, of which 202 belonged to the genera Aspergillus and Penicillium. Molecular identification using β-tubulin (BenA) gene sequencing revealed six Aspergillus and six Penicillium species, forming two well-supported phylogenetic clades. Aspergillus parasiticus was the most dominant species. Mycotoxin screening confirmed AFB1 production in 20 isolates, all identified as A. parasiticus, while no OTA-producing strains were detected. The predominance of aflatoxigenic species on H. halys indicates that it may play a previously underrecognized role in the dispersal of mycotoxigenic fungi in agroecosystems.

Molecular chaperones are central to cellular protein homeostasis. In mammals, protein misfolding diseases and aging cause inflammation and progressive tissue loss, in correlation with the accumulation of toxic protein aggregates and the defective expression of chaperone genes. Bacteria and non-diseased, non-aged eukaryotic cells effectively respond to heat shock by inducing the accumulation of heat-shock proteins (HSPs), many of which molecular chaperones involved in protein homeostasis, in reducing stress damages and promoting cellular recovery and thermotolerance. We performed a meta-analysis of published microarray data and compared expression profiles of HSP genes from mammalian and plant cells in response to heat or isothermal treatments with drugs. The differences and overlaps between HSP and chaperone genes were analyzed, and expression patterns were clustered and organized in a network. HSPs and chaperones only partly overlapped. Heat-shock induced a subset of chaperones primarily targeted to the cytoplasm and organdíes but not to the endoplasmic reticulum, which organized into a network with a central core of Hsp90s, Hsp70s, and sHSPs. Heat was best mimicked by isothermal treatments with Hsp90 inhibitors, whereas less toxic drugs, some of which nonsteroidal anti-inflammatory drugs, weakly expressed different subsets of Hsp chaperones. This type of analysis may uncover new HSP-inducing drugs to improve protein homeostasis in misfolding and aging diseases.

In the crowded environment of human cells, folding of nascent polypeptides and refolding of stress-unfolded proteins is error prone. Accumulation of cytotoxic misfolded and aggregated species may cause cell death, tissue loss, degenerative conformational diseases, and aging. Nevertheless, young cells effectively express a network of molecular chaperones and folding enzymes, termed here \"the chaperome,\" which can prevent formation of potentially harmful misfolded protein conformers and use the energy of adenosine triphosphate (ATP) to rehabilitate already formed toxic aggregates into native functional proteins. In an attempt to extend knowledge of chaperome mechanisms in cellular proteostasis, we performed a meta-analysis of human chaperome using high-throughput proteomic data from 11 immortalized human cell lines. Chaperome polypeptides were about 10 % of total protein mass of human cells, half of which were Hsp90s and Hsp70s. Knowledge of cellular concentrations and ratios among chaperome polypeptides provided a novel basis to understand mechanisms by which the Hsp60, Hsp70, Hsp90, and small heat shock proteins (HSPs), in collaboration with cochaperones and folding enzymes, assist de novo protein folding, import polypeptides into organelles, unfold stress-destabilized toxic conformers, and control the conformal activity of native proteins in the crowded environment of the cell. Proteomic data also provided means to distinguish between stable components of chaperone core machineries and dynamic regulatory cochaperones.

Chaperonins are cage-like complexes in which nonnative polypeptides prone to aggregation are thought to reach their native state optimally. However, they also may use ATP to unfold stably bound misfolded polypeptides and mediate the out-of-cage native refolding of large proteins. Here, we show that even without ATP and GroES, both GroEL and the eukaryotic chaperonin containing t-complex polypeptide 1 (CCT/TRiC) can unfold stable misfolded polypeptide conformers and readily release them from the access ways to the cage. Reconciling earlier disparate experimental observations to ours, we present a comprehensive model whereby following unfolding on the upper cavity, in-cage confinement is not needed for the released intermediates to slowly reach their native state in solution. As over-sticky intermediates occasionally stall the catalytic unfoldase sites, GroES mobile loops and ATP are necessary to dissociate the inhibitory species and regenerate the unfolding activity. Thus, chaperonin rings are not obligate confining antiaggregation cages. They are polypeptide unfoldases that can iteratively convert stable off-pathway conformers into functional proteins.

The ability to express tightly controlled amounts of endogenous and recombinant proteins in plant cells is an essential tool for research and biotechnology. Here, the inducibility of the soybean heat-shock Gmhsp17.3B promoter was addressed in the moss Physcomitrella patens, using beta-glucuronidase (GUS) and an F-actin marker (GFP-talin) as reporter proteins. In stably transformed moss lines, Gmhsp17.3B-driven GUS expression was extremely low at 25 degrees C. In contrast, a short non-damaging heat-treatment at 38 degrees C rapidly induced reporter expression over three orders of magnitude, enabling GUS accumulation and the labelling of F-actin cytoskeleton in all cell types and tissues. Induction levels were tightly proportional to the temperature and duration of the heat treatment, allowing fine-tuning of protein expression. Repeated heating/cooling cycles led to the massive GUS accumulation, up to 2.3% of the total soluble proteins. The anti-inflammatory drug acetyl salicylic acid (ASA) and the membrane-fluidiser benzyl alcohol (BA) also induced GUS expression at 25 degrees C, allowing the production of recombinant proteins without heat-treatment. The Gmhsp17.3B promoter thus provides a reliable versatile conditional promoter for the controlled expression of recombinant proteins in the moss P. patens.

Soil fungi are key drivers of terrestrial ecosystem functioning, contributing to organic matter decomposition, nutrient cycling, and plant–microorganism interactions. Despite their importance, the global distribution and structural biases of public sequence records for soil fungi remain incompletely characterized. In this study, we analyzed soil-associated fungal DNA sequences retrieved from the NCBI GenBank database using a custom R-based bioinformatics pipeline. Following filtering and metadata standardization, 544,554 filtered sequence records were obtained. The taxonomic composition of the dataset consisted primarily of Ascomycota (69.62%), followed by Basidiomycota, Glomeromycota, and Mucoromycota, with Trichoderma, Penicillium, and Aspergillus representing the most frequent genera. The geographic distribution revealed strong sampling bias, with China and the United States accounting for over one-third of all records. Ecological metadata indicated that rhizospheric and forest soils were the most common sources of the deposited sequences. At the same time, gene marker analyses confirmed the widespread use of the ITS region as the primary fungal barcode. Sequence diversity analyses revealed continental variation, with Europe and Asia showing higher medians, while the ordination highlighted clustering of sequence profiles, particularly among records from extreme environments. This study demonstrates the potential of public sequence databases for large-scale biodiversity assessments while highlighting the influence of sampling bias and the limitations of metadata.

The 'in planta' visualization of F-actin in all cells and in all developmental stages of a plant is a challenging problem. By using the soybean heat inducible Gmhsp17.3B promoter instead of a constitutive promoter, we have been able to label all cells in various developmental stages of the moss Physcomitrella patens, through a precise temperature tuning of the expression of green fluorescent protein (GFP)-talin. A short moderate heat treatment was sufficient to induce proper labeling of the actin cytoskeleton and to allow the visualization of time-dependent organization of F-actin structures without impairment of cell viability. In growing moss cells, dense converging arrays of F-actin structures were present at the growing tips of protonema cell, and at the localization of branching. Protonema and leaf cells contained a network of thick actin cables; during de-differentiation of leaf cells into new protonema filaments, the thick bundled actin network disappeared, and a new highly polarized F-actin network formed. The controlled expression of GFP-talin through an inducible promoter improves significantly the 'in planta' imaging of actin.