Biology subjects

Ghirardo, A.

Publications and source records attributed to Ghirardo, A..

8 recordsLinked to original sources

bioRxiv2026

GSNOR-dependent nitric oxide homeostasis promotes recovery from repeated climate stress across generations in Arabidopsis thaliana

Climate change exposes plants to recurrent and interacting stresses, yet the extent to which these effects persist across generations, and the mechanisms involved, remain unclear. We propagated Arabidopsis thaliana wild type (WT, Col-0) and nitric oxide homeostasis mutant gsnor1-3 (hereafter, gsnor-ko) for five successive generations. Plants were grown under control, drought, elevated CO2, O3, warm temperature, and combined treatment scenarios for the first three generations (G1-G3), followed by two recovery generations under control conditions (G4-G5). We quantified rosette growth, photosynthetic traits, seed production, and transcriptome dynamics by RNA-seq. Across environments, gsnor-ko showed reduced vegetative growth and reproductive output relative to WT. Transcriptomic responses were strongly scenario- and generation-dependent, with the largest differential expression shifts observed under warm-climate and combined-treatment conditions. Compared with WT, gsnor-ko displayed broader gene overlap across generations and stronger retention or reconfiguration of stress-responsive states after stress withdrawal. Functional enrichment and candidate-gene analyses identified pathways/components linked to DNA methylation, heterochromatin maintenance, histone ubiquitination, m6A RNA regulation, and methyl-donor metabolism. Together, these results support a model in which GSNOR activity promotes transcriptomic recovery after repeated climate stress, whereas impaired GSNOR function shifts responses toward multi-generational persistence and epigenetically associated regulatory reconfiguration. HighlightGSNOR-dependent nitric oxide homeostasis promotes transcriptomic resetting after repeated climate stress, whereas impaired NO homeostasis favours multigenerational persistence and chromatin- and RNA-linked regulatory reconfiguration. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=118 SRC="FIGDIR/small/742973v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@6031c6org.highwire.dtl.DTLVardef@163be5borg.highwire.dtl.DTLVardef@1665e9eorg.highwire.dtl.DTLVardef@1cde833_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2026

Dryland soil rewetting induces strong VOC emissions with potential to form ozone and aerosols

Biogenic volatile organic compounds (VOCs) significantly influence atmospheric chemistry, yet the importance of microbial VOC emissions remains understudied. We investigate petrichor VOC emissions, the characteristic scent following rainfall after prolonged drought, in an aridity gradient across Israel, by simulating soil rewetting events. Rewetting triggered strong VOC fluxes (1-3.5 nmol m-2 s-1 ground area) dominated by sesquiterpenes and benzenoids, with emission patterns linked to climatic regions, soil aridity, and microbial community composition. Petrichor consisted of a complex bouquet of 58 VOCs, and the initial VOC burst resembled the CO2 pulse of the Birch effect. Petrichor emissions showed ozone and secondary organic aerosol formation potentials comparable in magnitude to those estimated for anthropogenic VOC sources in Israel. Despite compositional differences, emissions were of similar magnitudes across the aridity gradient. Given that drylands cover nearly half of Earths terrestrial surface and are expanding, these episodic microbial VOC emissions may represent a significant, previously overlooked source of reactive carbon with potential implications for regional and global atmospheric chemistry.

microbiology↗

bioRxiv2026

Fungal volatiles drive lifestyle-dependent, systemic metabolic reprogramming in poplar

O_LIRationale: Although trees encounter diverse fungal communities, it is unclear how they adjust their physiology in response to fungal ecological strategies before physical contact. We tested whether volatile organic compounds (VOCs) emitted by fungi are sufficient to induce systemic, lifestyle-consistent metabolic states in poplar roots and leaves. C_LIO_LIMethods: Populus x canescens roots were exposed to VOCs from a pathogen (Heterobasidion annosum), a saprotroph (Postia placenta) or an ectomycorrhizal mutualist (Laccaria bicolor) for six weeks in a contact-free pot-in-pot system. Untargeted LC-MS metabolomics characterized VOC-induced metabolic reprogramming in roots and leaves. C_LIO_LIKey results: Fungal VOC exposure alone reconfigured the metabolomes of roots and leaves, with strong discrimination between treatments despite belowground exposure. Poplar revealed a shared VOC-responsive component, but also fungus-specific programmes: pathogen VOCs produced a suppression-dominated systemic phenotype; saprotroph VOCs promoted lipid-centred metabolic activation; and mutualist VOCs elicited restrained, compatibility-consistent shifts with targeted pathway modulation. C_LIO_LIMain conclusion: Volatile-mediated surveillance allows trees to anticipate fungal lifestyle-associated cues and adjust systemic metabolism before physical contact occurs. This links airborne fungal cues to whole-plant physiological configuration and extends plant-fungal recognition beyond contact-dependent mechanisms. C_LI One-sentence summaryVolatile-mediated surveillance allows trees to anticipate fungal lifestyle and adjust systemic metabolism before physical contact occurs.

plant biology↗

bioRxiv2025

Volatile cues from pathogenic, mutualistic and saprotrophic fungi cause specific, fungus-dependent responses in poplar

Plants are exposed to complex interactions with belowground organisms, yet how they differentiate between mutualistic and pathogenic fungi before physical contact remains largely unknown. We exposed the roots of young Populus x canescens to volatile organic compounds (VOCs) emitted by either a pathogenic (Heterobasidion annosum), a saprotrophic (Postia placenta), or an ectomycorrhizal (Laccaria bicolor) fungus. VOC analysis of the shared rhizosphere headspace and leaf emissions revealed that poplar plants could perceive and respond to fungal identity solely through airborne cues. The root-zone headspace contained fungus-specific sesquiterpene fingerprints that remained similar after three and six weeks of co-cultivation: Pathogen-derived VOCs induced constant high sesquiterpene emissions from the root-zone, whereas mycorrhiza caused low but targeted emissions of specific sesquiterpenes. In contrast, saprotrophic VOCs caused a temporal shift in root-zone VOC pattern, with increased sesquiterpene emissions after six weeks. Fungal VOC exposure also altered leaf VOC emissions, enriching alkanes, esters and monoterpenes. Initially, leaf VOC emissions were fungal lifestyle-specific but they converged over time, indicating systemic signal integration of belowground signals. These findings demonstrate that trees can discriminate "friend-versus-foe" through VOCs alone, extending pattern-recognition theory beyond contact-dependent cues. Multivariate analyses suggested organ-specific chemical strategies: roots function as chemosensors decoding fungal volatilomes, while systemic adjustments shape aboveground VOC profiles. Understanding the plant response to fungal VOCs may offer potential for developing early pathogen diagnostics and further elucidate the volatile-mediated plant-fungal interactions.

plant biology↗

bioRxiv2025

Volatile-Mediated Plant Defense Networks: Field Evidence for Isoprene as a Short-Distance Immune Signal

Isoprene, the most abundant hydrocarbon emitted by vegetation, protects photosynthesis against oxidative and thermal stress and significantly impacts atmospheric chemistry. While laboratory studies suggest a role for isoprene in plant defense, its function in plant-plant communication under natural conditions remains unclear. Here, we demonstrate that isoprene acts as a signaling molecule, triggering systemic immune responses in neighboring plants against bacterial pathogens under field conditions. We established an experimental system using wild-type and transgenic silver birch (Betula pendula) lines engineered to emit varying levels of isoprene. Over two growing seasons, we examined the effects of birch-emitted volatile organic compounds on neighboring Arabidopsis thaliana, including wild-type and immune signaling mutants (llp1: legume lectin-like protein 1; jar1: jasmonate resistant 1). Isoprene emission rates positively correlated with systemic resistance in receiver plants, with higher emissions enhancing inhibition of Pseudomonas syringae growth. This immune response occurred independently of jasmonate signaling but required functional LLP1, suggesting a specific recognition pathway. By combining Arabidopsis mutant responses with birch volatile profiles, we confirmed that isoprene, rather than other terpenoids, mediates this effect. These findings reveal an unrecognized ecological function of isoprene as an airborne immune signal, establishing transgenic birch as a robust model for studying volatile-mediated plant defense networks in natural environments. Our results provide new insights into the molecular mechanisms underlying plant volatile perception and expand our understanding of chemical communication in terrestrial ecosystems. Significance StatementIsoprene, the most abundant volatile organic compound released by plants, protects against abiotic stress. Here, we demonstrate that isoprene also functions under ambient atmosphere as a short-distance immune signal, enhancing neighboring plants resistance to bacterial pathogens. This finding reveals a putative ecological role of isoprene in plant defense networks and suggests strategies for sustainable agriculture and forest management under environmental stress.

plant biology↗

bioRxiv2024

Co-cultivation with Azolla affects the metabolome of whole rice plant beyond canonical inorganic nitrogen fertilization

Azolla spp. are floating ferns used for centuries as biofertilizers to enrich the soil with inorganic nitrogen and improve rice yields. In this study, rice plants were grown together with Azolla by maintaining a low and constant concentration of inorganic nitrogen. We employed a combination of non-targeted metabolomics, chemometrics, and molecular networking to dissect the impact of Azolla co-cultivation on the metabolome of rice roots-and leaves. Our analyses revealed that Azolla releases a broad range of metabolites in the culture medium, mainly comprising small peptides and flavonoids. Moreover, in rice co-cultivated with Azolla, we observed a systematic response in the upregulation of metabolites that started from the roots and, over time, shifted to the leaves. During the early stages of co-cultivation, Azolla led to the accumulation of small peptides, lipids, and carbohydrates in roots, and flavonoid glycosides and carbohydrates in leaves of rice. Consistent with these results, transcriptomics analysis of rice roots indicated significant changes in the expression of genes coding for small peptide and lipid transporters, and genes involved in amino acid salvage and biosynthesis. Overall, our study highlights novel growth-promoting effects of Azolla on rice which could facilitate the development of sustainable techniques to increase yields. HighlightsThe aquatic fern Azolla synthesizes and releases a broad range of growth promoting metabolites (i.e. small peptides) that can be absorbed by the roots of co-cultivated rice plants

plant biology↗

bioRxiv2024

Deciphering plant-beneficial fungal interactions: Unravelling metabolic diversity that underpins communication between Laccaria bicolor and Trichoderma

With over 250 known species, the genus Trichoderma (Ascomycota, Hypocreaceae) is found in various soils, on plant surfaces and as plant endophytes. While Trichoderma species are known as mycoparasites, their antagonistic behaviour can also negatively affect other beneficial fungi, such as mycorrhizal fungi. To gain insight into the metabolic signals involved in the interactions between the ectomycorrhizal fungus (ECM) Laccaria bicolor (Basidomycota, Hydnangiaceae), and different mycoparasitic Trichoderma spp. (T. harzianum strains WM24a1, MS8a1 and ES8g1, and T. atrobrunneum), we performed in vitro dual-confrontation experiments. We studied the volatile organic compounds (VOCs), hyphal metabolomes and soluble metabolites released by each of the fungi in various co-cultivation scenarios. The results revealed an altered growth of the mycelia depending on the degree of contact: When Trichoderma spp. and L. bicolor shared only the same headspace, Trichoderma spp. growth was at least partially inhibited, whereas in direct contact the growth of L. bicolor was impaired. Distinct strain- and species-specific changes in hyphal metabolites, in exudates and volatile emission were revealed from each of the studied fungi. We identified both core metabolite profiles and interaction-specific metabolic responses that were related to carbohydrate, lipid, nucleotide, energy and amino acid metabolisms. Volatile and soluble metabolites revealed temporal and spatial adjustments in dual cultures compared to solitary cultures, suggesting rapid contact-dependent adaptations and demonstrating the dynamic communication mechanisms between Trichoderma spp. and the ECM. These results suggest a central role for both emitted and secreted fungal metabolites in the fungal non-self-recognition and in interaction with each other.

microbiology↗

bioRxiv2020

Nitric oxide coordinates histone acetylation and expression of genes involved in growth/development and stress response

Nitric oxide (NO) is a signaling molecule with multiple regulatory functions in plant physiology and stress response. Besides direct effects on the transcriptional machinery, NO can fulfill its signaling function via epigenetic mechanisms. We report that light intensity-dependent changes in NO correlate with changes in global histone acetylation (H3, H3K9 and H3K9/K14) in Arabidopsis thaliana wild-type leaves and that this correlation depends on S-nitrosoglutathione reductase and histone deacetylase 6. The activity of histone deacetylase 6 was sensitive to NO, which demonstrates that NO participates in regulation of histone acetylation. ChIP-seq and RNA-seq analyses revealed that NO is involved in the metabolic switch from growth and development to stress response. This coordinating function of NO might be of special importance in adaptation to a changing environment and could therefore be a promising starting point to mitigating the negative effects of climate change on plant productivity.

plant biology↗