Rita de Cássia Monteiro-Batista

Cellular energy homeostasis relies on the precise exchange of nucleotides across subcellular compartments. The transport of ADP and ATP is essential for maintaining cellular energy balance. Transporters of these molecules are abundant proteins in the mitochondrial membrane, mediating their exchange between the mitochondrial matrix and the cytosol. In this study, we investigated the function of ADP/ATP Carrier 1 (AAC1) in plants to understand whether its regulation and function are similar to those described in animal and yeast systems. Our results revealed that AAC1 specifically transports ADP and ATP, while aac1 mutants displayed lower O2 consumption without evident decreases in cytosolic ATP levels. However, total adenylate profiling revealed altered adenylate balance and reduced adenylate energy charge in aac1 roots, indicating that reduced AAC1 function perturbs energy homeostasis beyond changes in ATP content alone. AAC1 was also required for proper mitochondrial structure, as aac1 mutant mitochondria exhibited a less electron-dense matrix and occasional absence of cristae. Suppressing AAC1 expression in plants altered vegetative and reproductive growth, reducing leaf number and root elongation while increasing silique size and seed weight. These findings provide novel insight into the role of AAC1 in mitochondrial energy dynamics. Biochemical analyses show a high specificity of AAC1 for adenine nucleotides, facilitating ADP/ATP exchange driven by the mitochondrial membrane potential, while excluding monophosphates and divalent ATP complexes. By correlating these biochemical characteristics with impaired mitochondrial respiration, altered adenylate balance, ultrastructural defects, and altered energy allocation, our study highlights the broader physiological impacts of disrupted adenylate transport mediated by AAC1.

Summary: The NADPH‐dependent thioredoxin reductase/thioredoxin (NTR/TRX) system plays a central role in maintaining redox homeostasis of the cell by transferring electrons from NADPH to target proteins though NTR and TRX, thereby modulating cysteine redox states and regulating enzyme activity. However, the specific contribution of the extraplastidial NTR/TRX system to plant acclimation to elevated CO ₂ (eCO ₂ ) remains poorly understood. Here, we investigated the physiological and metabolic responses of Arabidopsis mutants deficient in mitochondrial TRXo1 ( trxo1 ) or in the cytosolic/mitochondrial/nuclear thioredoxin reductases NTRA/NTRB ( ntrantrb ) alongside the wild‐type (WT), grown under ambient (aCO ₂ ; 400 ppm) and eCO ₂ (800 ppm) CO ₂ conditions. The stomatal closure induced by abscisic acid or eCO ₂ was partially compromised in ntrantrb double mutant. The stomatal density decreased in WT and ntrantrb plants under eCO ₂ , while did not change in trxo1 lines. The mutants showed much higher increases in rosette biomass under eCO ₂ compared to WT. This was associated with alterations in both primary and secondary metabolisms, but not to the level of NAD(P)(H), and reduced glutathione/oxidized glutathione (GSH : GSSG) ratio. Our results indicate that TRXo1 and NTRA/B play key roles in regulating stomatal development/movement and both primary and secondary metabolisms, thereby impacting plant acclimation to eCO ₂ .

The transport of metabolites across the inner mitochondrial membrane (IMM) is crucial for maintaining energy balance and efficient distribution of metabolic intermediates between cellular compartments. Under abiotic stress, mitochondrial function becomes particularly critical, activating complex signaling pathways essential for plant stress responses. These pathways modulate stress-responsive gene expression, influencing key physiological processes such as cell respiration and senescence, helping plants adapt to stress. Recent studies have emphasized the importance of finely tuned regulation of mitochondrial metabolite transport through the IMM, particularly under stress conditions, to optimize plant survival and resilience. This review summarizes current knowledge of the possible roles of mitochondrial transport proteins and their contributions to plant adaptation under abiotic stress.

O déficit hídrico é um dos fatores que mais limitam a produtividade das cultuas agrícolas. O ácido salicílico (AS) é um hormônio vegetal que possui um importante papel em resposta a estresses ambientais, incluindo estresse por privação hídrica. O manjericão (Ocimum basilicum L.) é uma planta sensível ao estresse hídrico e seu cultivo pode ser fortemente afetado por períodos prolongados de seca. Com isso, o objetivo do nosso trabalho foi avaliar o possível papel atenuador do AS em resposta ao estresse hídrico em duas cultivares de manjericão. O experimento foi conduzido em casa de vegetação da Universidade Federal do Agreste de Pernambuco. O delineamento experimental foi inteiramente casualizado, com oito tratamentos, sendo duas variedades de manjericão (roxo e verde), duas formas de aplicação do AS (com e sem aplicação) e duas formas de irrigação (irrigado e sem irrigação). A concentração de ácido salicílico usada foi de 2mM e sua aplicação foi exógena. Quanto aos resultados, observou-se uma redução de 15,7% da massa seca da parte aérea das plantas de manjericão quando submetidas a déficit hídrico em relação às plantas irrigadas. Foi observado diferenças significativas na taxa fotossintética das duas variedades de manjericão quando expostas ao AS. Esses resultados sugerem que o uso de AS na concentração de 2mM contribuiu positivamente tanto para o crescimento das plantas de manjericão submetidas a estresse hídrico quanto para as plantas irrigadas.

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.

Drought stress is a critical factor affecting plant growth and development. Understanding the effects of drought on the physiology of medicinal plants can contribute to the implementation of better water management techniques and promote a sustainable production. This study aimed to evaluate the influence of water stress on the growth and development of Mentha spicata L. plants. A completely randomized design was used, with two water conditions: irrigated and non-irrigated. The water deficit negatively affected the dry weight of roots and shoots, with a decrease in the transpiration rate and chlorophyll content, potentially impairing the photosynthetic activity. However, the essential oil production was not affected in plants subjected to water deficiency, indicating that the essential oil production may be more resilient to drought stress in this species.