ABC transporters are ancient and ubiquitous nutrient transport systems in bacteria and play a central role in defining lifestyles. Periplasmic solute-binding proteins (SBPs) are components that deliver ligands to their translocation machinery. SBPs have diversified to bind a wide range of ligands with high specificity and affinity. However, accurate assignment of cognate ligands remains a challenging problem in SBPs. Urea metabolism plays an important role in the nitrogen cycle; anthropogenic sources account for more than half of global nitrogen fertilizer. We report identification of urea-binding proteins within a large SBP sequence family that encodes diverse functions. By combining genetic linkage between SBPs, ABC transporter components, enzymes or transcription factors, we accurately identified cognate ligands, as we verified experimentally by biophysical characterization of ligand binding and crystallographic determination of the urea complex of a thermostable urea-binding homolog. Using three-dimensional structure information, these functional assignments were extrapolated to other members in the sequence family lacking genetic linkage information, which revealed that only a fraction bind urea. Using the same combined approaches, we also inferred that other family members bind various short-chain amides, aliphatic amino acids (leucine, isoleucine, valine), γ -aminobutyrate, and as yet unknown ligands. Comparative structural analysis revealed structural adaptations that encode diversification in these SBPs. Systematic assignment of ligands to SBP sequence families is key to understanding bacterial lifestyles, and also provides a rich source of biosensors for clinical and environmental analysis, such as the thermostable urea-binding protein identified here.

Insecticide resistance is a global concern and requires immediate attention to manage dreadful insect pests. One of the resistance mechanisms adopted by insects is through ATP-binding cassette (ABC) transporter proteins. These proteins rapidly transport and eliminate the insecticidal molecules across the lipid membranes (Phase III detoxification mechanism). In the present study, we investigated the potential role of ABC transporter genes in imparting insecticide resistance in field-collected insecticide resistant larvae of eggplant shoot and fruit borer (Leucinodes orbonalis; Crambidae: Lepidoptera). Dose-mortality bioassays against five insecticidal molecules revealed moderate to high levels of insecticide resistance (32.2. to 134.1-fold). Thirty-one genes encoding ABC transporter proteins were mined from the transcriptome resources of L. orbonalis. They were classified under eight sub-families (ABCA to ABCH). Phylogenetic analysis indicated ABCG is the most divergent, composed of nine genes as compared to many other insects. Transcriptome analysis of the insecticide resistant and susceptible strains of L. orbonalis revealed differential expression of 13 ABC transporter genes. The altered expression of these genes was further validated using qRT-PCR. The knockdown studies indicated the involvement of ABCD1 and ABCG2 genes in chlorantraniliprole resistance in the insecticide-resistant strain of L. orbonalis. This study unveils the additional mechanisms employed by L. orbonalis in resisting insecticide toxicity through accelerated excretion mode. These ABCD and ABCG family genes could be candidate targets in developing genome-assisted pest management strategies in the future.

ATP-binding cassette (ABC) transporters are vital for plant growth and development as they facilitate the transport of essential molecules. Despite the family\'s significance, limited information exists about its functional distinctions in Citrus medica. Our study identified 119 genes encoding ABC transporter proteins in the C. medica genome. Through an evolutionary tree and qPCR analysis, two ABC genes, CmABCB19 and CmABCC10, were implicated in C. medica fruit development, showing upregulation in normal fruits compared to malformed fruits. CmABCB19 was found to localize to the plasma membrane of Nicotiana tabacum, exhibiting indole-3-acetic acid (IAA) efflux activity in the yeast mutant strain yap1. CmABCC10, a tonoplast-localized transporter, exhibited efflux of diosmin, nobiletin, and naringin, with rutin influx in strain ycf1. Transgenic expression of CmABCB19 and CmABCC10 in Arabidopsis thaliana induced alterations in auxin and flavonoid content, impacting silique and seed size. This effect was attributed to the modulation of structural genes in the auxin biosynthesis (YUC5/9, CYP79B2, CYP83B1, SUR1) and flavonoid biosynthesis (4CL2/3, CHS, CHI, FLS1/3) pathways. In summary, the functional characterization of CmABCB19 and CmABCC10 illuminates auxin and flavonoid transport, offering insights into their interplay with biosynthetic pathways and providing a foundation for understanding the transporter\'s role in fruit development.

ABCA4 is an ATP-binding cassette (ABC) transporter that prevents the buildup of toxic retinoid compounds by facilitating the transport of N-retinylidene-phosphatidylethanolamine across membranes of rod and cone photoreceptor cells. Over 1500 missense mutations in ABCA4, many in the nucleotide-binding domains (NBDs), have been genetically linked to Stargardt disease. Here, we show by cryo-EM that ABCA4 is converted from an open outward conformation to a closed conformation upon the binding of adenylyl-imidodiphosphate. Structural information and biochemical studies were used to further define the role of the NBDs in the functional properties of ABCA4 and the mechanisms by which mutations lead to the loss in activity. We show that ATPase activity in both NBDs is required for the functional activity of ABCA4. Mutations in Walker A asparagine residues cause a severe reduction in substrate-activated ATPase activity due to the loss in polar interactions with residues within the D-loops of the opposing NBD. The structural basis for how disease mutations in other NBD residues, including the R1108C, R2077W, R2107H, and L2027F, affect the structure and function of ABCA4 is described. Collectively, our studies provide insight into the structure and function of ABCA4 and mechanisms underlying Stargardt disease.

Drug resistance in melanoma is a major hindrance in cancer therapy. Growth hormone (GH) plays a pivotal role in contributing to the resistance to chemotherapy. Knocking down or blocking the GH receptor has been shown to sensitize the tumor cells to chemotherapy. Extensive studies have demonstrated that exosomes, a subset of extracellular vesicles, play an important role in drug resistance by transferring key factors to sensitize cancer cells to chemotherapy. In this study, we explore how GH modulates exosomal cargoes from melanoma cells and their role in drug resistance. We treated the melanoma cells with GH, doxorubicin, and the GHR antagonist, pegvisomant, and analyzed the exosomes released. Additionally, we administered these exosomes to the recipient cells. The GH-treated melanoma cells released exosomes with elevated levels of ABC transporters (ABCC1 and ABCB1), N-cadherin, and MMP2, enhancing drug resistance and migration in the recipient cells. GHR antagonism reduced these exosomal levels, restoring drug sensitivity and attenuating migration. Overall, our findings highlight a novel role of GH in modulating exosomal cargoes that drive chemoresistance and metastasis in melanoma. This understanding provides insights into the mechanisms of GH in melanoma chemoresistance and suggests GHR antagonism as a potential therapy to overcome chemoresistance in melanoma treatment.

Per- and polyfluoroalkyl (PFAS) substances are a type of chemical compound unique for their multiple carbon-fluorine bonds, imbuing them with strength and environmental permanence. While legacy substances have been phased out due to human health risks, short-chain and alternative PFAS remain omnipresent. However, a detailed explanation for the pathways through which PFAS interact on a cellular and molecular level is still largely unknown, and the human health effects remain mechanistically unexplained. Of particular interest when focusing on this topic are the interactions between these exogenous chemicals and plasma and membrane proteins. Such proteins include serum albumin which can transport PFAS throughout the body, solute carrier proteins (SLC) and ATP binding cassette (ABC) transporters which are able to move PFAS into and out of cells, and proteins and nuclear receptors which interact with PFAS intracellularly. ABC transporters as a family have little available human data despite being responsible for the export of endogenous substances and drugs throughout the body. The multifactorial regulation of these crucial transporters is affected directly and indirectly by PFAS. Changes, which can include alterations to membrane transport activity and differences in protein expression, vary greatly depending on the specific PFAS and protein of interest. Together, the myriad of changes caused by understudied PFAS exposure to a class of understudied proteins crucial to cellular function and drug treatments has not been fully explored regarding human health and presents room for further exploration. This critical work aims to provide a novel framework of existing human data on PFAS and ABC transporters, allowing for future advancement and investigation into human transporter activity, mechanisms of regulation, and interactions with emerging contaminants.

Cancer drug resistance poses a significant obstacle to successful chemotherapy, primarily driven by the activity of ATP-binding cassette (ABC) transporters, which actively efflux chemotherapeutic agents from cancer cells, reducing their intracellular concentrations and therapeutic efficacy. Recent studies have highlighted the pivotal role of long noncoding RNAs (lncRNAs) in regulating this resistance, positioning them as crucial modulators of ABC transporter function. lncRNAs, once considered transcriptional noise, are now recognized for their complex regulatory capabilities at various cellular levels, including chromatin modification, transcription, and post-transcriptional processing. This review synthesizes current research demonstrating how lncRNAs influence cancer drug resistance by modulating the expression and activity of ABC transporters. lncRNAs can act as molecular sponges, sequestering microRNAs that would otherwise downregulate ABC transporter genes. Additionally, they can alter the epigenetic landscape of these genes, affecting their transcriptional activity. Mechanistic insights reveal that lncRNAs contribute to the activity of ABC transporters, thereby altering the efflux of chemotherapeutic drugs and promoting drug resistance. Understanding these interactions provides a new perspective on the molecular basis of chemoresistance, emphasizing the regulatory network of lncRNAs and ABC transporters. This knowledge not only deepens our understanding of the biological mechanisms underlying drug resistance but also suggests novel therapeutic strategies. In conclusion, the intricate interplay between lncRNAs and ABC transporters is crucial for developing innovative solutions to combat cancer drug resistance, underscoring the importance of continued research in this field.

BACKGROUND: In the field of ornamental horticulture, phenotypic mutations, particularly in leaf color, are of great interest due to their potential in developing new plant varieties. The introduction of variegated leaf traits in plants like Heliopsis helianthoides, a perennial herbaceous species with ecological adaptability, provides a rich resource for molecular breeding and research on pigment metabolism and photosynthesis. We aimed to explore the mechanism of leaf variegation of Heliopsis helianthoides (using HY2021F1-0915 variegated mutant named HY, and green-leaf control check named CK in 2020 April, May and June) by analyzing the transcriptome and metabolome.
RESULTS: Leaf color and physiological parameters were found to be significantly different between HY and CK types. Chlorophyll content of HY was lower than that of CK samples. Combined with the result of Weighted Gene Co-expression Network Analysis (WGCNA), 26 consistently downregulated differentially expressed genes (DEGs) were screened in HY compared to CK subtypes. Among the DEGs, 9 genes were verified to be downregulated in HY than CK by qRT-PCR. The reduction of chlorophyll content in HY might be due to the downregulation of FSD2. Low expression level of PFE2, annotated as ferritin-4, might also contribute to the interveinal chlorosis of HY. Based on metabolome data, differential metabolites (DEMs) between HY and CK samples were significantly enriched on ABC transporters in three months. By integrating DEGs and DEMs, they were enriched on carotenoids pathway. Downregulation of four carotenoid pigments might be one of the reasons for HY\'s light color.
CONCLUSIONS: FSD2 and PFE2 (ferritin-4) were identified as key genes which likely contribute to the reduced chlorophyll content and interveinal chlorosis observed in HY. The differential metabolites were significantly enriched in ABC transporters. Carotenoid biosynthesis pathway was highlighted with decreased pigments in HY individuals. These findings not only enhance our understanding of leaf variegation mechanisms but also offer valuable insights for future plant breeding strategies aimed at preserving and enhancing variegated-leaf traits in ornamental plants.

Excessive accumulation of chromium (Cr) causes severe damage to both physiological and biochemical processes and consequently growth repression in plants. Hexavalent chromium [Cr(VI)]-elicited alterations in plants have been widely elucidated at either physiological or molecular level, whereas little is known about trivalent chromium [Cr(III)]. Here, we found that both Cr(III) and Cr(VI) significantly inhibited root growth in rice plants. However, rice plants under Cr(VI) showed significantly less inhibition in root growth than those under Cr(III) at low levels, which might be attributed to the different hormetic effects of Cr(III) and Cr(VI) on rice plants. It was unexpected that Cr(III) could be actively taken up by rice roots similarly to Cr(VI); whereas they exhibited different kinetic uptake patterns. Furthermore, root-to-shoot Cr translocation under Cr(VI) was much lower than that under Cr(III). These results indicate that the uptake, translocation, and toxicity of Cr(III) differed greatly from those of Cr(VI). Transcriptome profiling of rice roots revealed that a series of gene families involved in detoxification, including ATP-binding cassette (ABC) transporters, multidrug and toxic compound extrusion proteins (MATEs), and Tau class glutathione S-transferases (GSTUs), were significantly associated with Cr accumulation and detoxification in rice roots. In addition, much more members of these gene families were upregulated by Cr(VI) compared to Cr(III), suggesting their vital roles in Cr uptake, translocation, and detoxification, especially under Cr(VI) stress. Further comparison of gstu9 and gstu10/50 mutants with their wild type confirmed that GSTUs play complex roles in the intracellular Cr transport and redox homeostasis during Cr(III) or Cr(VI) stress. Taken together, our findings provides new insights into the differential behaviors of Cr(III) and Cr(VI) in rice roots, as well as new candidate genes such as OsABCs and OsGSTUs, to further elucidate the mechanisms of the uptake, translocation, and detoxification of Cr(III) and Cr(VI).

Metabolomics has been used extensively to identify crucial molecules and biochemical effects induced by environmental factors. To understand the effects of acute low-salinity stress on Fenneropenaeus chinensis, intestinal histological examination and untargeted metabonomic analysis of F. chinensis were performed after exposure to a salinity of 15 ppt for 3, 7, and 14 d. The histological examination revealed that acute stress resulted in most epithelial cells rupturing, leading to the dispersion of nuclei in the intestinal lumen after 14 days. Metabolomics analysis identified numerous differentially expressed metabolites (DEMs) at different time points after exposure to low-salinity stress, in which some DEMs were steadily downregulated at the early stage of stress and then gradually upregulated. We further screened 14 overlapping DEMs, in which other DEMs decreased significantly during low-salinity stress, apart from L-palmitoylcarnitine and vitamin A, with enrichments in phenylalanine, tyrosine and tryptophan biosynthesis, fatty acid and retinol metabolism, and ABC transporters. ABC transporters exhibit significant abnormalities and play a vital role in low-salinity stress. This study provides valuable insights into the molecular mechanisms underlying the responses of F. chinensis to acute salinity stress.