The biological legacy of sulfur: A roadmap to the future

Chemodiversity of sulfur-containing metabolites emphasizing the ecophysiology of Allium plants and the developmental innovations in bulb formation

Sulfur (S) metabolism has played a critical role in the evolution of life, serving as an energy source for early biochemical pathways like dissimilatory S reduction and anoxygenic photosynthesis. Across kingdoms, S metabolism displays remarkable diversity. S-containing metabolites like glucosinolates (GLSs) in Brassicaceae and S-alk(en)ylcysteine sulfoxides in Allium species illustrate the ecological and evolutionary significance of S-containing compounds. These metabolites contribute to defense, homeostasis, and ecological interactions, with mechanisms like enzymatic hydrolysis releasing bioactive molecules such as allicin. Further, advances in transcriptomics and biochemical studies have revealed the genetic underpinnings of S metabolism and specialized pathways in bulb-forming Allium species. The role extends to ecological interactions by modulating S-associated defense pathways. This integrative understanding of S metabolism underscores its evolutionary, physiological, and ecological importance.

Adaptive modifications in plant sulfur metabolism over evolutionary time

Sulfur (S) is an essential element for life on Earth. Plants are able to take up and utilize sulfate (SO42-), the most oxidized inorganic form of S compounds on Earth, through the reductive S assimilatory pathway that couples with photosynthetic energy conversion. Organic S compounds are subsequently synthesized in plants and made accessible to animals, primarily as the amino acid methionine. Thus, plant S metabolism clearly has nutritional importance in the global food chain. S metabolites may be part of redox regulation and drivers of essential metabolic pathways as cofactors and prosthetic groups, such as Fe-S centers, CoA, thiamine, and lipoic acid. The evolution of the S metabolic pathways and enzymes reflects the critical importance of functional innovation and diversifications. Here we review the major evolutionary alterations that took place in S metabolism across different scales and outline research directions that may take advantage of understanding the evolutionary adaptations.

The role of sulfur compounds in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common respiratory disease that brings about great social and economic burden, with oxidative stress and inflammation affecting the whole disease progress. Sulfur compounds such as hydrogen sulfide (H₂S), thiols, and persulfides/polysulfides have intrinsic antioxidant and anti-inflammatory ability, which is engaged in the pathophysiological process of COPD. Hydrogen sulfide mainly exhibits its function by S-sulfidation of the cysteine residue of the targeted proteins. It also interacts with nitric oxide and acts as a potential biomarker for the COPD phenotype. Thiols’ redox buffer such as the glutathione redox couple is a major non-enzymatic redox buffer reflecting the oxidative stress in the organism. The disturbance of redox buffers was often detected in patients with COPD, and redressing the balance could delay COPD exacerbation. Sulfane sulfur refers to a divalent sulfur atom bonded with another sulfur atom. Among them, persulfides and polysulfides have an evolutionarily conserved modification with antiaging effects. Sulfur compounds and their relative signaling pathways are also associated with the development of comorbidities in COPD. Synthetic compounds which can release H₂S and persulfides in the organism have gradually been developed. Naturally extracted sulfur compounds with pharmacological effects also aroused great interest. This study discussed the biological functions and mechanisms of sulfur compounds in regulating COPD and its comorbidities.

Co-overexpression of AtSAT1 and EcPAPR improves seed nutritional value in maize

Maize seeds synthesize insufficient levels of the essential amino acid methionine (Met) to support animal and livestock growth. Serine acetyltransferase1 (SAT1) and 3'-phosphoadenosine-5'-phosphosulfate reductase (PAPR) are key control points for sulfur assimilation into Cys and Met biosynthesis. Two high-MET maize lines pRbcS:AtSAT1 and pRbcS:EcPAPR were obtained through metabolic engineering recently, and their total Met was increased by 1.4- and 1.57-fold, respectively, compared to the wild type. The highest Met maize line, pRbcS:AtSAT1-pRbcS:EcPAPR, was created by stacking the two transgenes, causing total Met to increase 2.24-fold. However, the pRbcS:AtSAT1-pRbcS:EcPAPR plants displayed progressively severe defects in plant growth, including early senescence, stunting, and dwarfing, indicating that excessive sulfur assimilation has an adverse effect on plant development. To explore the mechanism of correlation between Met biosynthesis in maize leaves and storage proteins in developing endosperm, the transcriptomes of the sixth leaf at stage V9 and 18 DAP endosperm of pRbcS:AtSAT1, pRbcS:AtSAT1-pRbcS:EcPAPR, and the null segregants were quantified and analyzed. In pRbcS:AtSAT1-pRbcS:EcPAPR, 3274 genes in leaves (1505 up- and 1769 downregulated) and 679 genes in the endosperm (327 up- and 352 downregulated) were differentially expressed. Gene ontology (GO) and KEGG (Kyoto encyclopedia of genes and genomes) analyses revealed that many genes were associated with Met homeostasis, including transcription factors and genes involved in cysteine and Met metabolism, glutathione metabolism, plant hormone signal transduction, and oxidation-reduction. The data from gene network analysis demonstrated that two genes, serine/threonine-protein kinase (CCR3) and heat shock 70 kDa protein (HSP), were localized in the core of the leaves and endosperm regulation networks, respectively. The results of this study provide insights into the diverse mechanisms that underlie the ideal establishment of enhanced Met levels in maize seeds.

Nutritional Properties of Baobab Pulp from Different Angolan Origins

The baobab tree (Adansonia digitata L.) is found widely in the forests and savannas of sub-Saharan Africa. The baobab fruit has a sour and slightly sweet taste and is widely consumed by the natives, thus containing a high nutritional value and providing a source of income for rural people. This study aimed to compare the nutritional composition of baobab fruit pulp from different localities in the Namibe province (Angola). Twenty samples of baobab pulp were collected in markets of the four municipalities of Namibe. The results obtained showed that there is some geographic location dependence on nutritional and functional composition. The municipality of Camucuio showed samples with higher fibre content (56.62 g/100 g) and vitamin C (288.9 mg/100 g). Samples from the Virei municipality stood out for their antioxidant activity (1936 mmol TE/100 g), high K content (42.4 mg/g) and higher values of protein (2.42 g/100 g). The samples collected in the municipality of Bibala stood out for their high contents of carbohydrates (28.1 g/100 g), total phenolic compounds (972 mg GAE/100 g) and Ca (3.80 mg/g). Despite the differences in origin, the high nutritional value of baobab fruit has the potential to improve the diet of thousands of people in Africa qualitatively.

Elemental Composition of Commercial Herbal Tea Plants and Respective Infusions

This study evaluated the elemental composition of 25 herbal tea plants commonly used in infusions by Portuguese consumers and the contribution to the elemental daily intake of some essential elements. Hydrocotyle asiatica (L.), Matricaria chamomilla (L.), and Melissa officinalis (L.) samples are a rich source of K with around 6.0 mg g−1 while the Asteraceae Silybum marianum (L.) and Echinacea angustifolia (DC.) exhibited 4.9 and 5.6 mg g−1 Ca, respectively. The highest concentrations of S and Zn were noted in Hydrocotyle asiatica (L.), while the highest concentration of Sr was found in Cassia angustifolia (Vahl.). In general, a large variability in the concentrations among different families and plant organs had been observed, except Cu with levels around 30 μg g−1. The principal component analysis (PCA) showed positive correlations between Zn and S and Sr and Ca, also revealing that Hydrocotyle asiatica (L.), Echinacea angustifolia (DC.), Silybum marianum (L.), and Cassia angustifolia (Vahl.) samples, stands out about all other samples regarding the enrichment of macro and micronutrients. The elemental solubility of macronutrients in the infusion is greater than the micronutrient solubility, despite the contribution to the recommended daily intake was weak. As a whole, Cynara scolymus (L.) and Hibiscus sabdariffa (L.) are the species with the best elemental solubilities, followed by Hydrocotyle asiatica (L.). No harmful elements, such as As and Pb, were observed in both the raw material and the infusions.