Plants use the plant hormone auxin to incorporate environmental cues into their growth and development to shape the final form. Temperature is an important modulator of all aspects of plant function and growth. In this work, we uncover temperature-regulated accumulation and solubility of members of the AUXIN RESPONSE FACTOR transcription factor family. We determine that ARF7 and ARF19 proteins rapidly hyperaccumulate in response to elevated temperature. Furthermore, we find that diffuse concentrations of ARF protein increase under elevated temperature, consistent with increased solubility. Temperature-driven ARF hyperaccumulation is not fully dependent on the well-established temperature response pathways. We find that natural variation in thermoregulated ARF accumulation is correlated with thermomorphogenesis, suggesting that this is a dial switch in plant temperature response. Regulated ARF thermoaccumulation provides a layer of complexity in shaping and plant growth and form, allowing plants to respond rapidly and persistently to elevated temperatures by modulating levels of nuclear ARF protein accumulation.
The Mediator complex interacts with transcription factors to guide the assembly of the Pre-initiation complex in promoter DNA. It also interacts with hormone signaling components, connecting hormone signaling to gene expression, serving as a hub for signal integration. Despite its role being essential, some Mediator subunits have specific roles. Here, we characterized the role of the MED3 subunit of Arabidopsis thaliana. We obtained null med3 mutants by CRISPR Cas9 and show that MED3 promotes flowering in a photoperiod and temperature independent manner. med3 mutants behave similarly to autonomous pathway mutants and we show that late flowering is due to high expression of FLOWERING LOCUS C. However, we also show that exogenous application of gibberellic acid (GA) to med3 mutants drastically changes its architecture, leading to a disproportionately higher number of cauline leaves with respect to rosette leaves. These findings suggest that GAs more effectively promote bolting of med3 mutants, but delay flower appearance later, suggesting that med3 mutants are more sensitive to GAs during reproductive development. Finally, we obtained transcriptomic data showing that ABA response genes are expressed at lower levels in med3 mutants, and show that med3 mutants are less sensitive to ABA during germination. Given the antagonistic roles of GA and ABA, MED3 may also have a role in balancing the relative sensitivity to these hormones.
ABSTRACT Pseudomonas aeruginosa is a human opportunistic pathogen, capable of producing a wide range of metabolites, including pyomelanin, which results from alterations in tyrosine catabolism. In contrast, melanin synthesis from tryptophan has never been reported in Pseudomonas . In this study, we applied an integrated multi-omics approach to characterize physiological adaptations associated with the emergence of a tryptophan-associated melanin-like pigment in P. aeruginosa PAH, a persistently re-isolated strain from a cystic fibrosis patient. Structural analysis revealed the production of a previously unreported melanin-like polymer produced under tryptophan supplementation, coexisting with a pyomelanin-like soluble fraction. This melanin exhibited iron-reduction capacity, supporting a potential physiological role in iron acquisition within the infective niche. Genome analysis identified mutations affecting iron acquisition, including genes involved in pyoverdine biosynthesis. Transcriptomic profiling revealed a coordinated reprogramming of iron homeostasis, characterized not only by the downregulation of pyoverdine-associated genes but also by altered expression of alternative siderophore systems and a broader set of genes, such as redox response pathways. Non-targeting metabolomic analyses uncovered the accumulation of indole-derived compounds. Inhibitors of tyrosine and tryptophan catabolism demonstrated a metabolic shift between these pathways. Notably, iron availability emerged as a key regulator of this system, with iron limitation promoting pigment production and associated metabolic states. Integrating these data sets, we developed an integrative model linking iron homeostasis, genomic variation, transcriptional and metabolic reprogramming, and melanin production in P. aeruginosa PAH. Overall, tryptophan arises as a key compound for melanin production in a Pseudomonas strain, expanding the diversity of melanins synthesized by this genus. IMPORTANCE This study reveals a previously unrecognized way by which Pseudomonas aeruginosa can produce melanin, a protective pigment linked to survival and persistence in hostile environments. Here, we report how a novel melanin pigment, produced in tryptophan-supplemented media, can reduce iron and is linked to iron homeostasis in a clinical P. aeruginosa strain. Employing a multi-omics approach, we show that this pathway operates primarily through anthranilate and indolic intermediates and is favored under iron-limited conditions. This finding deepens current understanding about pigment diversity in bacteria and highlights the remarkable metabolic flexibility of P. aeruginosa during infection. Since the same phenotype was observed again in year-later isolates from the same patient, our results suggest a potential role of this trait in long-term infection and adaptation.
Brucella infection is frequently acquired by inhalation, but the pathogen disseminates systemically from the lungs. However, little is known about the interaction of Brucella spp. with the airways. Using a 3D air-exposed organotypic human bronchial tissue model (polarized 16HBE14o- bronchial epithelial cells grown over a collagen matrix containing MRC-5 lung fibroblasts), we analyzed Brucella abortus replication, translocation and cytokine responses over prolonged post-infection times. Apically inoculated B. abortus invaded, replicated and persisted during the whole follow-up (16 days) within the bronchial tissue without inducing cytotoxicity. Viable bacteria were also detected in the conditioned medium (CM) since day five post-infection, indicating release from the basolateral side. In parallel experiments, no invasion or bacterial release was detected for Escherichia coli. The levels of IL-6, IL-8 and MCP-1 were increased in CM from Brucella-infected 3D cultures and in monocultures of polarized bronchial epithelial cells or lung fibroblasts. Collagenase/gelatinase activity was increased in 3D cultures and MRC-5 monocultures. Infection transference from bronchial cells to lung fibroblasts was documented using monocultures. An immune cross-talk was detected, as cytokine levels were increased in fibroblasts stimulated with bronchial CM, and vice versa. These results suggest that the bronchial mucosa can sustain B. abortus persistence, replication and dissemination, and that it induces a proinflammatory response to which both epithelial cells and fibroblasts contribute.
Planning husbandry tasks and experiments with Drosophila melanogaster requires converting a target date into development times that depend on the rearing temperature. This calculation needs to be done for each cross, genotype, and temperature, and the risk of error grows quickly. Available laboratory management tools let users register stocks, crosses, and track them, but they do not create schedules based on a clear, adjustable thermal model. To fill that gap, we developed DrosoTracker, a self-contained web application that works offline and predicts Drosophila development with a thermal summation model recalibrated through regression on data from Powsner (1935) (T0 = 11.78 °C, DD = 116.38 °C·days, R² = 0.997). The model offers an optional two-level calibration driven by user observations. A wild-type strain first adjusts the model to the laboratory’s own conditions. Then each genotype is calibrated against that reference using a random-effects shrinkage estimator that accounts for measurement error and between-batch variability. The model creates schedules for husbandry tasks, evaluates adult cohort survival with the Kaplan-Meier estimator and the log-rank test, and calculates sample size for lifespan studies using Schoenfeld’s formula. The quantitative components were checked against independent references, including R’s survival package and manual calculations. Ongoing work is focused on validating the calibrated model using cohorts specifically bred for this purpose. DrosoTracker runs entirely in the browser, stores data locally, and is available in English and Spanish. ### Competing Interest Statement The authors have declared no competing interest. The DrosoTracker application, the calibration script, the estimator simulation and sensitivity scripts, the test suite and the primary data used to fit the thermal-summation model are openly available at under the MIT licence, which permits use, modification and redistribution provided that the copyright notice and the licence text are retained. The release described here (v1.0) is archived at Zenodo, DOI: 10.5281/zenodo.21867404. The live application runs at . No restrictions apply to data access. Intramural Fund of Fundacion Científica Felipe Fiorellino, Universidad Maimonides, grant PIP 11220210100502CO from CONICET, directed by A. C. Liberman, and by grant AARG-D-23-1050853 from the Alzheimer's Association to promote Diversity, awarded to A. C. Liberman
