Auxiliadora Oliveira Martins

Lysine metabolism connects amino acid biosynthesis with mitochondrial respiration through coordinated synthesis and degradation pathways that interface with the tricarboxylic acid (TCA) cycle and the mitochondrial electron transport chain (mETC). The critical role of this pathway is underscored by the embryonic lethality of the Arabidopsis L,L-diaminopimelate aminotransferase mutant (dapat), which is defective in a key step of lysine biosynthesis. Hypomorphic dapat mutant plants exhibit profound metabolic reprogramming and a constitutive energy-limited phenotype under non-stress conditions, suggesting that lysine biosynthesis contributes to basal metabolic homeostasis. We therefore hypothesized that impaired lysine biosynthesis restricts metabolic flexibility, but that changes in CO2 availability may partially compensate through carbon and nitrogen remodeling. To test this, we performed comprehensive metabolite profiling of wild-type and dapat mutant plants under low-, ambient-, and elevated-CO2 conditions. Elevated CO2 (eCO2) induced broad reorganization of carbon and nitrogen metabolism in both genotypes, reducing photorespiratory and stress-associated amino acids and modulating key metabolic ratios, including glycine/serine and malate/aspartate, in a genotype- and time-dependent manner. Proteomics revealed DAPAT photosynthetic compensation under ambient CO2, with RuBisCO over-accumulation and suppressed TOR activity, as indicated by decreased RPS6 phosphorylation, which eCO2 restored in parallel with phenotypic rescue. These adjustments were associated with partial attenuation of the DAPAT metabolic imbalance. Our findings reveal functional connections among lysine biosynthesis, photorespiration, and CO2-responsive metabolic flexibility, demonstrating that lysine metabolism serves as a regulatory node linking amino acid homeostasis to carbon availability and respiratory adjustment. This provides mechanistic insight into how plants maintain energy balance under fluctuating CO2 environments.

Global warming is increasing the frequency and intensity of high-temperature episodes, limiting plant productivity. However, the molecular mechanisms integrating primary metabolism with the heat stress response remains poorly understood. Here, we show that lysine biosynthesis contributes to the coordination of physiological, metabolic and transcriptional responses to heat stress in Arabidopsis thaliana. We compared wild-type, the lysine-biosynthesis mutant dapat, and the salicylic acid (SA)-biosynthesis and signaling mutants sid2-1 and npr1-3 under prolonged warming (6C above control for 7 days) and heat shock (38C for 6 h), followed by recovery. We assessed growth, gas exchange, photosynthetic performance, free SA, salicylic acid glucoside (SAG), salicylic acid glucose ester (SGE), and total SA content, primary metabolite profiles, heat-stress-responsive gene expression and transcriptome-wide changes by RNA sequencing. Before heat stress, dapat mutant presented a distinct metabolic state, marked by amino-acid accumulation, altered organic-acid profiles, reduced soluble sugars and elevated endogenous SA. This metabolic configuration persisted during prolonged warming, whereas WT and SA-pathway mutants underwent more dynamic reprogramming. Heat shock, by contrast, elicited a more convergent response across genotypes. Despite reduced basal PSII efficiency, dapat maintained photosynthetic performance during prolonged warming and recovered. Its transcriptional response, however, differed from that of WT and SA-pathway mutants: selected heat-responsive genes were constitutively or more strongly expressed, whereas some canonical heat-stress regulators showed weaker induction after heat shock. RNA-seq further revealed a largely conserved core heat-shock response but genotype-dependent regulation of defense, hormone and amino-acid-metabolism programs, particularly during recovery. Together, these findings indicate that impaired DAPAT activity establishes a metabolically primed but energetically constrained state that reshapes gas exchange, photosynthetic acclimation and heat-responsive transcription. Lysine homeostasis therefore emerges as a regulatory node linking primary metabolism and SA accumulation with SA-dependent and SA-independent components of heat-stress acclimation.

Plant tissue culture is an important clonal propagation technique that enhances plantlet production of species with limited survival/rooting capacity in nurseries. This study investigated the effects of gas exchange rates, sucrose concentrations, and light quality on the micropropagation of two hybrid clones of Corymbia torelliana × C. citriodora . Propagule productivity, morphophysiological development and metabolic responses in vitro, as well as ex vitro survival of microcuttings were assessed. Explants were cultured in sealed vessels without gas-permeable membranes [14 µL L⁻¹ s⁻¹ CO₂] or with two membranes [25 µL L⁻¹ s⁻¹ CO₂], using JADS culture medium supplemented with 0, 15, or 30 g L⁻¹ sucrose. Based on these results, an optimal gas exchange –sucrose condition was selected, and a subsequent experiment evaluated different light sources: fluorescent light, white LED, red/blue LED (3:1), and blue LED. A gas exchange rate of 14 µL L⁻¹ s⁻¹ combined with 15 g L⁻¹ sucrose increased propagation productivity. In contrast, a higher gas exchange rate (25 µL L⁻¹ s⁻¹) enhanced primary metabolites, organic acids, amino acids, and superoxide dismutase activity, indicating enhanced metabolic and antioxidant responses. The presence of membranes and sucrose promoted greater photosynthetic activity, while ex vitro survival was up to threefold greater when membranes and 15 g L⁻¹ sucrose were used. Light quality significantly affected growth: white LED reduced propagation productivity, blue light promoted shoot elongation, and red/blue light increased biomass accumulation, while the ex vitro survival was nine- to fifteen-fold greater when plantlets were micropropagated under fluorescent light compared with white LED.

Aluminum (Al) contamination in acidic soils severely limits plant growth and development. This study investigated the mechanisms and timing of Al toxicity in Pfaffia glomerata , a medicinal species of growing pharmacological interest. Based on the hypothesis that P. glomerata mitigates Al toxicity through tissue-specific adjustments in redox metabolism, accumulation of protective metabolites, and regulation of genes involved in cell wall structure and 20-hydroxyecdysone biosynthesis, plantlets were grown in vitro for 40 days under five Al concentrations (0, 200, 400, 600, and 800 μM). Concentrations above 600 μM significantly impaired plant growth. Aluminum accumulated in both roots and leaves, indicating active translocation throughout the plant. Plants exposed to 600 μM Al exhibited increased levels of glucose and fructose, and to a lesser extent, sucrose and starch. Additionally, starch, proline, malate, and fumarate levels rose in response to Al stress, suggesting metabolic adjustments for stress mitigation. Elevated antioxidant enzyme activity and malondialdehyde accumulation in the roots indicated oxidative stress. At the molecular level, the expression of genes related to 20-hydroxyecdysone biosynthesis ( PgSpook and PgPhantom ) was downregulated in the roots, while genes involved in cell wall biosynthesis ( PgCCR , PgCAD , PgC4H ) were upregulated in the leaves and downregulated in the roots. These findings show that P. glomerata tolerates moderate Al stress via a multifaceted response involving morphological adjustments, redox regulation, metabolite accumulation, and differential gene expression. This is the first evidence of Al-induced downregulation of 20-hydroxyecdysone biosynthesis in a medicinal species and identifies novel molecular targets for enhancing stress tolerance in non-model plants.

Aluminum (Al) toxicity is the main factor limiting agricultural production in acidic soils around the world. In this scenario, melatonin (MET) has emerged as a promising approach to alleviate Al toxicity. Thus, we investigated morphophysiological responses of Pfaffia glomerata (Spreng.) Pedersen, a medicinal plant, to Al toxicity and MET application. Plants were grown in vitro for 40 days in MS medium (control) supplemented with Al, MET, and Al + MET. Aluminum had genotoxic effects, inducing DNA damages and endoreduplication, which resulted in growth arrest, mainly in roots. Al also decreased the photosynthetic rate and the contents of pigments, carbohydrates, amino acids, and proteins. On the other hand, all these effects were improved in plants supplemented with MET. This is supported by the up-accumulation of proteins involved in organic acids exudation (AHA2), photosynthesis (transketolase, rubisco activase, and photosystem I P700 apoprotein A2), amino acid biosynthesis (chorismate synthase 1 and aspartokinase/homoserine dehydrogenase), and cell expansion and differentiation (rough sheath 2, beta tubulin b6, and tubulin beta chain-like). Moreover, MET enhanced CAT, SOD, and GABA, reinforcing its antioxidant role and reducing DNA damage and endoreduplication, which preserved QC identity and root elongation. Al toxicity impaired growth and carbon–nitrogen metabolism, whereas MET mitigated these effects by boosting photosynthesis, antioxidant defenses, and Al sequestration, decreasing Al adherence to roots. Thus, MET serves as a protective molecule against Al toxicity in P. glomerata .

Water supply constraints limit crop yield across seasons and locations, restricting food production under diverse climate scenarios. Irrigation schedules that align with plant water demand at specific times of the day have been proposed to overcome limitations in the water supply. Watering crops in the morning has been associated with reductions in productivity, although the mechanisms underlying this phenomenon remain poorly understood. Here, we demonstrate that watering tomato (Solanum lycopersicum) at different times of the day alters the transcriptional patterns of genes controlling flowering induction. Dawn watering (DAW) triggered a strong repression of the single flower truss (SFT) gene, leading to metabolite accumulation and delayed development. Dusk-watered plants showed increased fruit production compared to DAW-treated plants. Our findings highlight how metabolism and development in tomato are remodeled by the timing of watering, suggesting strategies to enhance tomato water-use efficiency by incorporating time-specific watering practices in agriculture.