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Paracoccidioides brasiliensis is the agent of paracoccidioidomycosis (PCM), a cause of disease in healthy and immunocompromised persons in Latin America. The infection begins after inhalation of the fungal propagules and their thermo-dimorphic shift to yeast form. The development of the disease depends on factors associated with the host immune response and the infectious agent's characteristics, especially virulence. The oxidative stress response is an important virulence attribute in several fungi. In this study, we assessed the enzymatic repertoire of responses to oxidative stress in the Pb18 isolate with different degrees of virulence. The virulence of attenuated Pb18 (aPb18) strain was recovered after several animal passages. Virulent strain (vPb18) showed an effective fungal oxidative stress response and several genes involved in response to oxidative stress were up-regulated in this isolate. These genes expressed the same profile when we recovered the phenotypic virulence in attenuated strain aPb18. Our study demonstrated that attenuated P. brasiliensis recovered their virulence after serial animal passages (vPb18), and this process positively modulated the fungus's antioxidant repertoire.

Paracoccidioides brasiliensis and P. lutzii, thermally dimorphic fungi, are the causative agents of paracoccidioidomycosis (PCM). Paracoccidioides infection occurs when conidia or mycelium fragments are inhaled by the host, which causes the Paracoccidioides cells to transition to the yeast form. The development of disease requires conidia inside the host alveoli to differentiate into yeast cells in a temperature-dependent manner. We describe the presence of a two-component signal transduction system in P. brasiliensis, which we investigated by expression analysis of a hypothetical protein gene (PADG_07579) that showed high similarity with the dimorphism-regulating histidine kinase (DRK1) gene of Blastomyces dermatitidis and Histoplasma capsulatum. This gene was sensitive to environmental redox changes, which was demonstrated by a dose-dependent decrease in transcript levels after peroxide stimulation and a subtler decrease in transcript levels after NO stimulation. Furthermore, the higher PbDRK1 levels after treatment with increasing NaCl concentrations suggest that this histidine kinase can play a role as osmosensing. In the mycelium-yeast (M→Y) transition, PbDRK1 mRNA expression increased 14-fold after 24 h incubation at 37°C, consistent with similar observations in other virulent fungi. These results demonstrate that the PbDRK1 gene is differentially expressed during the dimorphic M→Y transition. Finally, when P. brasiliensis mycelium cells were exposed to a histidine kinase inhibitor and incubated at 37°C, there was a delay in the dimorphic M→Y transition, suggesting that histidine kinases could be targets of interest for PCM therapy. PbDRK1, a conserved histidine kinase, acts as a regulator of dimorphism in Paracoccidioides brasiliensis, participates in the response to osmotic stress and its virulence. Graphical Abstract Figure. PbDRK1, a conserved histidine kinase, acts as a regulator of dimorphism in Paracoccidioides brasiliensis, participates in the response to osmotic stress and its virulence.

The pivotal role of phytohormones during fruit development and ripening is considered established knowledge in plant biology. Perhaps less well-known is the growing body of evidence suggesting that organic acids play a key function in plant development and, in particular, in fruit development, maturation and ripening. Here, we critically review the connection between organic acids and the development of both climacteric and non-climacteric fruits. By analyzing the metabolic content of different fruits during their ontogenetic trajectory, we noticed that the content of organic acids in the early stages of fruit development is directly related to the supply of substrates for respiratory processes. Although different organic acid species can be found during fruit development in general, it appears that citrate and malate play major roles in this process, as they accumulate on a broad range of climacteric and non-climacteric fruits. We further highlight the functional significance of changes in organic acid profile in fruits due to either the manipulation of fruit-specific genes or the use of fruit-specific promoters. Despite the complexity behind the fluctuation in organic acid content during fruit development and ripening, we extend our understanding on the importance of organic acids on fruit metabolism and the need to further boost future research. We suggest that engineering organic acid metabolism could improve both qualitative and quantitative traits of crop fruits.

Although boron (B) is an element that has long been assumed to be an essential plant micronutrient, this assumption has been recently questioned. Cumulative evidence has demonstrated that the players associated with B uptake and translocation by plant roots include a sophisticated set of proteins used to cope with B levels in the soil solution. Here, we summarize compelling evidence supporting the essential role of B in mediating plant developmental programs. Overall, most plant species studied to date have exhibited specific B transporters with tight genetic coordination in response to B levels in the soil. These transporters can uptake B from the soil, which is a highly uncommon occurrence for toxic elements. Moreover, the current tools available to determine B levels cannot precisely determine B translocation dynamics. We posit that B plays a key role in plant metabolic activities. Its importance in the regulation of development of the root and shoot meristem is associated with plant developmental phase transitions, which are crucial processes in the completion of their life cycle. We provide further evidence that plants need to acquire sufficient amounts of B while protecting themselves from its toxic effects. Thus, the development of in vitro and in vivo approaches is required to accurately determine B levels, and subsequently, to define unambiguously the function of B in terrestrial plants.

Hexokinases (HXKs) and fructokinases (FRKs) are the only two families of enzymes in plants that have been identified as able to phosphorylate Glucose (Glc) and Fructose (Fru). Glc can only be phosphorylated in plants by HXKs, while Fru can be phosphorylated by either HXKs or FRKs. The various subcellular localizations of HXKs in plants indicate that they are involved in diverse functions, including anther dehiscence and pollen germination, stomatal closure in response to sugar levels, stomatal aperture and reducing transpiration. Its association with modulating programmed cell death, and responses to oxidative stress and pathogen infection (abiotic and biotic stresses) also have been reported. To extend our understanding about the function of HXK-like genes in the response of Prunus rootstocks to abiotic stress, we performed a detailed bioinformatic and functional analysis of hexokinase 3-like genes ( HXK3 s) from two Prunus rootstock genotypes, ‘M.2624’ ( Prunus cerasifera Ehrh ×  P. munsoniana W.Wight & Hedrick) and ‘M.F12/1’ ( P. avium L.), which are tolerant and sensitive to hypoxia stress, respectively. A previous large-scale transcriptome sequencing of roots of these rootstocks, showed that this HXK3-like gene that was highly induced in the tolerant genotype under hypoxia conditions. In silico analysis of gene promoters from M.2624 and M.F12/1 genotypes revealed regulatory elements that could explain differential transcriptional profiles of HXK3 genes. Subcellular localization was determinates by both bioinformatic prediction and expression of their protein fused to the green fluorescent protein (GFP) in protoplasts and transgenic plants of Arabidopsis. Both approaches showed that they are expressed in plastids. Metabolomics analysis of Arabidopsis plants ectopically expressing Prunus HXK3 genes revealed that content of several metabolites including phosphorylated sugars (G6P), starch and some metabolites associated with the TCA cycle were affected. These transgenic Arabidopsis plants showed improved tolerance to salt and drought stress under growth chamber conditions. Our results suggest that Prunus HXK3 is a potential candidate for enhancing tolerance to salt and drought stresses in stone fruit trees and other plants.

Monitoring nitrate in aquatic systems is of fundamental importance since its presence at high levels can result in adverse effects on human health. Thus, in this work, manufactured carbon black (CB)/polylactic acid (PLA)-based 3D-printed electrochemical sensors modified with electrodeposited silver particles (AgPs) for nitrate analysis in real water samples. Raman and FT-IR spectra, scanning electron microscopy images, and analysis by energy-dispersive spectroscopy confirmed the presence of AgPs on the porous carbonaceous surface. The preliminary electrochemical studies showed that using the modified electrode (CB-PLA/AgPs) an incredible increase in the electrochemical response (around 16.5-fold in terms of current density) was obtained for the electroreduction of nitrate at around − 1.08 V vs. Ag|AgCl|KCl (sat.) compared to the unmodified electrode (CB-PLA). The linear sweep voltammetry technique was employed whose instrumental parameters have been carefully optimized. Under optimized conditions, a linear range between 5 and 80 mg L −1 ( R 2  > 0.99) was achieved, with a detection limit of 2.7 mg L −1 , which is below the maximum level permitted (50 mg L −1 ) by the World Health Organization (WHO). Repeatability (intra-electrode, n  = 8) and reproducibility (inter-electrode, n  = 3) studies were performed, and RSDs < 2.1% were found, demonstrating good precision of the analysis and reproducible manufacturing process of the sensors. Moreover, the proposed sensor proved to be selective in the presence of other inorganic compounds frequently found in environmental waters. Importantly, in the recovery tests, percentage values between 91 and 117% confirmed the accuracy and reliability of the analyses. Thus, the developed strategy can be useful for nitrate sensing in real water samples in remote locations.

Among the adenylate carriers identified in Arabidopsis thaliana, only the AMP/ATP transporter ADNT1 shows increased expression in roots under waterlogging stress conditions. Here, we investigated the impact of a reduced expression of ADNT1 in A. thaliana plants submitted to waterlogging conditions. For this purpose, an adnt1 T-DNA mutant and two ADNT1 antisense lines were evaluated. Following waterlogging, ADNT1 deficiency resulted in a reduced maximum quantum yield of PSII electron transport (significantly for adnt1 and antisense Line 10), indicating a higher impact caused by the stress in the mutants. In addition, ADNT1 deficient lines showed higher levels of AMP in roots under nonstress condition. This result indicates that the downregulation of ADNT1 impacts the levels of adenylates. ADNT1-deficient plants exhibited a differential expression pattern of hypoxia-related genes with an increase in non-fermenting-related-kinase 1 (SnRK1) expression and upregulation of adenylate kinase (ADK) under stress and non-stress conditions. Together, these results indicated that the lower expression of ADNT1 is associated with an early “hypoxic status” due to the perturbation of the adenylate pool caused by reduced AMP import by mitochondria. This perturbation, which is sensed by SnRK1, results in a metabolic reprogramming associated with early induction of the fermentative pathway in ADNT1 deficient plants.

Chromoblastomycosis (CBM) is a neglected implantation mycosis prevalent in tropical climate zones, considered an occupational disease that affects impoverished rural populations. This retrospective study described clinical aspects of CBM in a hyperendemic area in Brazil and constructed a worldwide haplotype network of Fonsecaea spp. strains. The variables were collected from medical records using a standard report form, reporting 191 patients with CBM from Maranhão, Brazil. The mean age was 56.1 years, 168 (88%) patients were male and predominantly farmers (85.8%). The mean time of evolution of the disease until diagnosis was 9.4 years. Lower limbs (81.2%) and upper limbs (14.2%) were the main sites affected. Most patients exhibited verrucous (55%) and infiltrative plaque (48.2%). Fonsecaea spp. were identified in 136 cases and a haplotype network constructed with ITS sequences of 185 global strains revealed a total of 59 haplotypes exhibiting high haplotypic and low nucleotide diversities. No correlation was observed between the different haplotypes of Fonsecaea species and dermatological patterns, severity of disease or geographic distribution inside Maranhão. Data from this area contributed to better understanding the epidemiology of CBM. For the first time, a robust haplotype network with Fonsecaea strains reveals an evolutionary history with a recent population expansion.

Nitrogen (N) sources have been target in microalgae cultivation studies, considering their nutritional impact on growth and high costs. Here, we have evaluated the growth of Scenedesmus obliquus BR003, applying alternative low-cost culture media containing ammonium and urea, or combinations of both N sources. The culture media were applied for indoor and outdoor cultivation, followed by growth analyses and metabolic characterization. The alternative culture media B4 and L4 supported higher biomass production (1.4 g L−1) compared to BG11 (nitrate-based medium). In addition, the lipid percentage was higher for B4 (ammonium-based culture medium), reaching up to 25% DW. High contents of carbohydrates (60%) and proteins (40%) were also obtained in media with ammonium and urea, respectively. Considering the lower costs of alternative fertilizer-based media, using ammonium and/or urea as N sources, and the high lipid content observed, we suggest these media as viable for large-scale production of S. obliquus.

Malate is a central metabolite involved in a multiplicity of plant metabolic pathways, being associated with mitochondrial metabolism and playing significant roles in stomatal movements. Vacuolar malate transport has been characterized at the molecular level and is performed by at least one carrier protein and two channels in Arabidopsis (Arabidopsis thaliana) vacuoles. The absence of the Arabidopsis tonoplast Dicarboxylate Transporter (tDT) in the tdt knockout mutant was associated previously with an impaired accumulation of malate and fumarate in leaves. Here, we investigated the consequences of this lower accumulation on stomatal behavior and photosynthetic capacity as well as its putative metabolic impacts. Neither the stomatal conductance nor the kinetic responses to dark, light, or high CO₂ were highly affected in tdt plants. In addition, we did not observe any impact on stomatal aperture following incubation with abscisic acid, malate, or citrate. Furthermore, an effect on photosynthetic capacity was not observed in the mutant lines. However, leaf mitochondrial metabolism was affected in the tdt plants. Levels of the intermediates of the tricarboxylic acid cycle were altered, and increases in both light and dark respiration were observed. We conclude that manipulation of the tonoplastic organic acid transporter impacted mitochondrial metabolism, while the overall stomatal and photosynthetic capacity were unaffected.