L-Serine (Ser) and L-Glycine (Gly) are critically important for the overall functioning of primary metabolism. We investigated the interaction of the Phosphorylated Pathway of Ser Biosynthesis (PPSB) with the photorespiration-associated Glycolate Pathway of Ser Biosynthesis (GPSB) using Arabidopsis thaliana PPSB-deficient lines, GPSB-deficient mutants, and crosses of PPSB with GPSB mutants. PPSB-deficient lines mainly showed retarded primary root growth. Mutation of the photorespiratory enzyme Ser-hydroxymethyltransferase 1 (SHMT1) in a PPSB-deficient background resumed primary root growth and induced a change in the plant metabolic pattern between roots and shoots. Grafting experiments demonstrated that metabolic changes in shoots were responsible for the changes in double mutant development. PPSB disruption led to a reduction in nitrogen (N) and sulfur (S) contents in shoots and a general transcriptional response to nutrient deficiency. Disruption of SHMT1 boosted the Gly flux out of the photorespiratory cycle, which increased the levels of the one-carbon (1C) metabolite 5,10-methylene-tetrahydrofolate and S-adenosylmethionine. Furthermore, disrupting SHMT1 reverted the transcriptional response to N and S deprivation and increased N and S contents in shoots of PPSB-deficient-lines. Our work provides genetic evidence of the biological relevance of the Ser-Gly-1C metabolic network in N and S metabolism and in interorgan metabolic homeostasis.

In response to the challenge posed by antimicrobial resistance and the demand for innovative anticancer drugs, the aim of this study was to examine the potential source of natural antioxidant, antimicrobial, and anticancer compounds from purple flowers of Bougainvillea glabra. The dried purple flower of B. glabra was sequentially extracted with hexane, ethyl acetate, methanol, and water. The extracts were used for investigating antioxidants, antimicrobial activity, anticancer properties, and phytochemical composition. The methanol extraction exhibited the highest total phenolic content and in vitro antioxidant activity. The hexane and ethyl acetate extracts exhibited antimicrobial activity against a broad range of microorganisms in both American type of culture collection (ATCC) and clinical strains, while the methanol extract displayed a narrower antimicrobial profile that implied the promise of B. glabra as a developmental reservoir of specific antimicrobial agents. Notably, the hexane extract demonstrated the most promising anticancer activity against various cancer cell lines, including lung cancer (A549), colon cancer (HT-29), breast cancer (MCF-7), and bile duct cancer (KKU-213A). In conclusion, this study reveals the pharmaceutical potential of crude extracts from B. glabra flowers; thereby, paving the way for future exploration of these compounds within the drug development industry.

The transfer of one-carbon (C1) units is an integral part of cellular metabolism and is essential for the biosynthesis of nucleotides, amino acids, and cofactors, as well as for cellular methylation reactions. Within the plant cell, mitochondria are considered the hubs of one-carbon metabolism; however, the mechanisms and fluxes that distribute C1 units from the mitochondria throughout the cell are unknown. Formate, the anion of formic acid, is an intermediate of C1 metabolism and is converted to C1-tetrahydrofolate intermediates (C1 folates) or oxidized to CO2 by formate dehydrogenase. The presence of formate dehydrogenase in plant cells challenges the formate exchange between mitochondria and the cytosol, a basic principle of eukaryotic cellular and organellar C1 metabolism. Based on the biochemical and physiological characterization of Arabidopsis (Arabidopsis thaliana) formate dehydrogenase 1 (FDH1), we propose an FDH1-regulated C1 shunt linking mitochondrial and cytosolic C1 metabolism by formate exchange. Finally, we give a perspective on a cellular serine/formate shuttle that allows the distribution and transfer of C1 units according to the redox state within the compartments.

While the pursuit and development of novel drugs to combat emerging diseases is ongoing, many newly characterized compounds have been discovered in different parts of traditional medicinal plants. Numerous investigations have scrutinized the phytochemical properties of the leaf, flower, seed, and bark of Caesalpinia pulcherrima, revealing its noteworthy attributes as an herbal remedy employed in the treatment of diverse ailments. Our research aims to re-evaluate this medicinal plant, with a focus on the yellow flower, employing a sequential solvent extraction technique. Our findings revealed that a methanolic extract exhibited the highest antioxidant capacity in 3 colorimetric antioxidant assays: DPPH, ABTS, and FRAP. Extracts from the yellow flower of C. pulcherrima exhibited antimicrobial resistance against a wide range of both pathogenic Gram-positive and Acinetobacter baumannii isolates. Additionally, these extracts manifested anticancer properties against various cancer cell lines. Our investigation marks the first inhibition of cell proliferation of the bile duct cancer cell line (KKU-213A) by this crude extract. This study contributes valuable insights to the ongoing research of potential phytochemical properties from the yellow flower of C. pulcherrima, providing additional information for further research on the separation and purification of crude extracts from the yellow flower of C. pulcherrima. Ultimately, our study presents a promising approach to specifically screening phytochemicals from C. pulcherrima flowers that could be developed into new antibiotic drugs or anticancer agents. HIGHLIGHTS Methanol was identified as the most effective solvent for extracting antioxidant compounds from Caesalpinia pulcherrima yellow flowers. Extracts obtained using hexane, ethyl acetate, and aqueous solutions exhibited antimicrobial activity against all tested gram-positive bacteria and some gram-negative strains. For the 1st time, this study demonstrated that ethyl acetate and methanol extracts showed significant cytotoxicity against the bile duct cancer cell line KKU-213A, indicating their potential for anticancer drug development. GRAPHICAL ABSTRACT

The global prevalence of multidrug-resistant (MDR) bacteria represents an urgent public health challenge, emphasizing the critical need for novel antimicrobial agents. MDR Acinetobacter baumannii , a nosocomial pathogen of critical global concern owing to its capacity to acquire and disseminate antimicrobial resistance, was employed as a bacterial model to investigate the antimicrobial potential of natural products derived from Caesalpinia pulcherrima (L.) Sw. (Fabaceae). This medicinal plant represents a promising reservoir of novel bioactive compounds; however, its molecular effects on the A. baumannii proteome had not previously been characterized. The partially purified ethyl acetate fraction of C. pulcherrima flowers (CPF4) exhibited potent bactericidal activity against susceptible A. baumannii (minimum inhibitory concentration and minimum bactericidal concentration = 31.25 µg/mL), and time-resolved label-free quantitative LC-MS/MS proteomics was subsequently performed on MDR A. baumannii cultures treated with CPF4 at 24 h, 48 h, and 72 h post-treatment alongside untreated controls in biological triplicate, with differential protein expression assessed using differential expression of quantified mass spectrometry data. No significantly differentially expressed proteins were detected at 24 h or 48 h relative to the control, indicating that the proteomic effects of CPF4 manifest predominantly at the late treatment stage. In contrast, a robust late-phase response was identified at 72 h, comprising the coordinated induction of proteins associated with DNA damage repair, transcriptional regulation, and cell surface glycosylation remodeling. The sensor histidine kinase PmrB was significantly upregulated at 72 h vs 48 h (adjusted P = 0.029), implicating the PmrA/PmrB two-component system in late-phase colistin tolerance acquisition under sustained CPF4 exposure. IMPORTANCE: These findings provide mechanistic insight into the adaptive survival strategies employed by multidrug-resistant Acinetobacter baumannii in response to plant-derived antimicrobial challenge and support the further development of Caesalpinia pulcherrima -derived natural products as candidate antimicrobial agents.