Region Leucine Zipper Transcription Factors Research Articles

Functional Identification of Malus halliana MhbZIP23 Gene Demonstrates That It Enhances Saline-Alkali Stress Tolerance in Arabidopsis thaliana.

Saline-alkali stress is a significant abiotic stress that restricts plant growth globally. Basic region leucine zipper (bZIP) transcription factor proteins are widely involved in plants in response to abiotic stress such as saline-alkali stress. Based on transcriptome and quantitative real-time PCR (qRT-PCR), we found that the MhbZIP23 gene could respond to saline-alkali stress. Despite this discovery, the underlying mechanism by which the MhbZIP23 transcription factor responds to saline-alkaline stress remains unexplored. To address this gap in knowledge, we successfully cloned the MhbZIP23 (MD05G1121500) gene from Malus halliana for heterologous expression in Arabidopsis thaliana, facilitating the investigation of its functional role in stress response. Compared to the wild type (WT), Arabidopsis plants demonstrated enhanced growth and a lower degree of wilting when subjected to saline-alkali stress. Furthermore, several physiological indices of the plants altered under such stress conditions. The transgenic Arabidopsis plants (OE-5, 6, and 8), which grew normally, exhibited a higher chlorophyll content and had greater root length in comparison to the control check (CK). MhbZIP23 effectively regulated the levels of the osmoregulatory substance proline (Pro), enhanced the activities of antioxidant enzymes such as peroxidase (POD) and superoxide dismutase (SOD), and reduced the levels of malondialdehyde (MDA) and relative conductivity (REC). These actions improved the ability of plant cells in transgenic Arabidopsis to counteract ROS, as evidenced by the decreased accumulation of O2- and hydrogen peroxide (H2O2). In summary, the MhbZIP23 gene demonstrated effectiveness in alleviating saline-alkali stress in M. halliana, presenting itself as an outstanding resistance gene for apples to combat saline-alkali stress.

Signal Transduction of Transient Receptor Potential TRPM8 Channels: Role of PIP5K, Gq-Proteins, and c-Jun.

Transient receptor potential melastatin-8 (TRPM8) is a cation channel that is activated by cold and "cooling agents" such as menthol and icilin, which induce a cold sensation. The stimulation of TRPM8 activates an intracellular signaling cascade that ultimately leads to a change in the gene expression pattern of the cells. Here, we investigate the TRPM8-induced signaling pathway that links TRPM8 channel activation to gene transcription. Using a pharmacological approach, we show that the inhibition of phosphatidylinositol 4-phosphate 5 kinase α (PIP5K), an enzyme essential for the biosynthesis of phosphatidylinositol 4,5-bisphosphate, attenuates TRPM8-induced gene transcription. Analyzing the link between TRPM8 and Gq proteins, we show that the pharmacological inhibition of the βγ subunits impairs TRPM8 signaling. In addition, genetic studies show that TRPM8 requires an activated Gα subunit for signaling. In the nucleus, the TRPM8-induced signaling cascade triggers the activation of the transcription factor AP-1, a complex consisting of a dimer of basic region leucine zipper (bZIP) transcription factors. Here, we identify the bZIP protein c-Jun as an essential component of AP-1 within the TRPM8-induced signaling cascade. In summary, with PIP5K, Gq subunits, and c-Jun, we identified key molecules in TRPM8-induced signaling from the plasma membrane to the nucleus.

Androgen synthesis cell-specific CREBZF deficiency alters adrenal cortex steroid secretion and develops behavioral abnormalities in adult male mice.

The global challenge of male infertility is escalating, notably due to the decreased testosterone (T) synthesis in testicular Leydig cells under stress, underscoring the critical need for a more profound understanding of its regulatory mechanisms. CREBZF, a novel basic region-leucine zipper transcription factor, regulates testosterone synthesis in mouse Leydig cells invitro; however, further validation through invivo experiments is essential. Our study utilized Cyp17a1-Cre to knock out CREBZF in androgen-synthesis cells and explored the physiological roles of CREBZF in fertility, steroid hormone synthesis, and behaviors in adult male mice. Conditional knockout (cKO) CREBZF did not affect fertility and serum testosterone level in male mice. Primary Leydig cells isolated from CREBZF-cKO mice showed impaired testosterone secretion and decreased mRNA levels of Star, Cyp17a1, and Hsd3b1. Loss of CREBZF resulted in thickening of the adrenal cortex, especially X-zone, with elevated serum corticosterone and dehydroepiandrosterone levels and decreased serum dehydroepiandrosterone sulfate levels. Immunohistochemical staining revealed increased expression of StAR, Cyp11a1, and 17β-Hsd3 in the adrenal cortex of CREBZF-cKO mice, while the expression of AR was significantly reduced. Along with the histological changes and abnormal steroid levels in the adrenal gland, CREBZF-cKO mice showed higher anxiety-like behavior and impaired memory in the elevated plus maze and Barnes maze, respectively. In summary, CREBZF is dispensable for fertility, and CREBZF deficiency in Leydig cells promotes adrenal function in adult male mice. These results shed light on the requirement of CREBZF for fertility, adrenal steroid synthesis, and stress response in adult male mice, and contribute to understanding the crosstalk between testes and adrenal glands.

PhbZIP2 regulates photosynthesis-related genes in an intertidal macroalgae, Pyropia haitanensis, under stress.

Intertidal macroalgae are important research subjects in stress biology. Basic region-leucine zipper transcription factors (bZIPs) play an important regulatory role in the expression of target genes under abiotic stress. We herein identified a bZIP2 gene PhbZIP2 to regulate abiotic stress tolerance in Pyropia haitanensis, a representative intertidal macroalgal species. Cloning and sequencing of the cDNA characterized a BRLZ structure and an α coiled-coil structure between amino acids and Expression of PhbZIP2 was detected to upregulate under both high temperature and salt stresses. A DAP-seq analysis revealed the PhbZIP2-binding motifs of (T/C)TCCA(C/G) and A (A/G)AAA (G/A), which differed from the conserved motifs in plants. Overexpression of PhbZIP2 was indicative of a high temperature and salt stress tolerances in transgenic Chlamydomonas reinhardtii. It was suggested that PhbZIP2 was probably involved in regulating expression of the photosynthetic-related genes and the response to the abiotic stresses in P. haitanensis, which provide new insights for elucidating efficient adaptation strategies of intertidal macroalgae.

BmC/EBPZ gene is essential for the larval growth and development of silkworm, Bombyx mori.

The genetic male sterile line (GMS) of the silkworm Bombyx mori is a recessive mutant that is naturally mutated from the wild-type 898WB strain. One of the major characteristics of the GMS mutant is its small larvae. Through positional cloning, candidate genes for the GMS mutant were located in a region approximately 800.5kb long on the 24th linkage group of the silkworm. One of the genes was Bombyx mori CCAAT/enhancer-binding protein zeta (BmC/EBPZ), which is a member of the basic region-leucine zipper transcription factor family. Compared with the wild-type 898WB strain, the GMS mutant features a 9bp insertion in the 3'end of open reading frame sequence of BmC/EBPZ gene. Moreover, the high expression level of the BmC/EBPZ gene in the testis suggests that the gene is involved in the regulation of reproduction-related genes. Using the CRISPR/Cas9-mediated knockout system, we found that the BmC/EBPZ knockout strains had the same phenotypes as the GMS mutant, that is, the larvae were small. However, the larvae of BmC/EBPZ knockout strains died during the development of the third instar. Therefore, the BmC/EBPZ gene was identified as the major gene responsible for GMS mutation.

Functional Analysis of PbbZIP11 Transcription Factor in Response to Cold Stress in Arabidopsis and Pear.

Cold stress is a prominent abiotic factor that adversely affects the growth and yield of pears, consequently restricting the cultivation range and resulting in substantial economic losses for the pear industry. Basic region-leucine zipper (bZIP) transcription factors are widely involved in multiple physiological and biochemical activities of plants, particularly in response to cold stress. In this study, the responsiveness of PbbZIP11 in pear to cold stress was investigated, and its role was explored by using pear callus and Arabidopsis thaliana. The findings revealed that overexpression of PbbZIP11 enhanced the tolerance of pear callus and Arabidopsis thaliana to cold stress. The antioxidant enzyme activities of transgenic plants were enhanced and the expression of C-repeat binding transcription factor (CBF) genes was increased as compared to wild-type plants. To better understand the biological function of PbbZIP11, mRNAs were isolated from overexpressed and wild-type Arabidopsis thaliana after cold stress for whole-genome sequencing. The results showed that the expression of some CBF downstream target genes changed after exposure to cold stress. The results suggested that the PbbZIP11 gene could participate in cold-stress signaling through the CBF-dependent pathway, which provides a theoretical basis for the PbbZIP11-mediated response to cold stress and for the genetic breeding of pear varieties with low-temperature tolerance.

The ATF4-RPS19BP1 Axis Modulates Ribosome Biogenesis to Promote Erythropoiesis

The function of hematopoietic stem cells (HSCs) and the process of hematopoiesis are intricately governed by a complex interplay of intrinsic programs and extrinsic signals from the microenvironment (Crane et al., Nat Rev Immunol, 2017). Previous work reported by our group and others has demonstrated that ATF4, a basic region-leucine zipper transcription factor, plays pivotal roles in fetal liver hematopoiesis, HSC maintenance, bone formation and tumorigenesis (Zhao et al., Blood, 2015; Sun et al., Sci Adv, 2021; Yang et al., Cell, 2004). However, the precise function of ATF4 in the bone marrow niche and how ATF4 regulates adult hematopoiesis remain largely unknown. Here, we employ four cell-type-specific mouse Cre lines to conditionally knock out Atf4 in Cdh5 + endothelial cells (ECs), Prx1 + bone marrow stromal cells (BMSCs), Osx + osteo-progenitor cells, and Mx1 + hematopoietic cells, and uncover the role of Atf4 in niche cells and hematopoiesis. We found that Atf4 deletion in BMSCs reduced BMSC numbers and impaired their CFU-F activity as well as differentiation toward osteoblasts, but spares hematopoiesis and HSC function in adult mice. Furthermore, Atf4 depletion in the ECs or osteo-progenitors of adult mice has a very mild effect on the BM hematopoiesis and HSC maintenance. Intriguingly, Atf4 depletion in the hematopoietic system resulted in severe anemia. More than 70% of the Mx1cre; Atf4 fl/fl (Δ/Δ) mice gradually died from anemia. Atf4 deficiency markedly reduced the frequency of erythroid progenitor cells (EPCs) (including MEP, PreCFU-E, and CFU-E cells) and impaired their CFU-E and BFU-E colony-forming ability. Atf4 depletion severely impaired the repopulation ability of BM cells and the self-renewal capacity of HSCs. Single cell RNA-seq (scRNA-seq) analysis of BM Lin -cKit + cells confirmed the defects of erythropoiesis after Atf4 depletion. The absence of ATF4 compelled early erythroid progenitors to enter the S phase, which led to replication stress and in turn activated both the DNA damage response and apoptosis. Subsequently, we conducted an integrative analysis of the genes that were identified as downregulated in MEPs by RNA-seq, ATAC-seq, and H3K4me3 Cut&Tag and genes that were identified as downregulated in erythroid progenitors (i.e., PreMegE, Ery1, and Ery2) by scRNA-seq, which predicted Rps19bp1 as the top target gene of Atf4. Luciferase reporter and quantitative chromatin immunoprecipitation (qChIP) assays confirmed that ATF4 was a transcriptional activator of Rps19bp1. Downregulation of Rps19bp1 caused by Atf4 deletion led to decreased assembles of 40S proteins, such as RPS3, RPS6 and RPS19. O-propargyl-puromycin (OP-Puro) incorporation and SUnSET assay further confirmed the global protein synthesis defect in Atf4-deficient MEP cells. The protein synthesis defects and impaired erythropoiesis were rescued upon RPS19BP1 overexpression in Atf4 knockdown MEL cell line or BM cKit + cells from Atf4-deficient mice. Ribosome profiling of CMP cells from Δ/Δ and fl/fl mice further demonstrated that the expression of proteins involved in ribosome biogenesis was significantly lower in Atf4-depleted than in wildtype CMP cells. The expression of gene sets linked to PreCFU-E signature was also lower in Atf4-depleted than in wildtype CMPs, suggesting that the reduction in ribosome biogenesis significantly affected the translation efficiency of erythroid-related pathway components, thereby impeding erythroid lineage commitment. Finally, we demonstrate that under conditions of 5-fluorouracil-induced stress, Atf4 depletion impedes the recovery of hematopoietic lineages, which requires efficient ribosome biogenesis. Taken together, we demonstrated that, unlike in the fetal liver, ATF4 governs adult HSC function and erythropoiesis in a cell-intrinsic manner. We revealed a novel role for ATF4 in erythropoiesis, which links it to RPS19BP1, ribosome biogenesis and protein translation. Our findings have highlighted the crucial importance of protein synthesis regulation during erythroid lineage commitment. This discovery will likely have extended implications for understanding and treating ribosomopathy-associated erythroid failure.

The cytosolic N-terminal region of heterologously-expressed transmembrane channel-like protein 1 (TMC1) can be cleaved in HEK293 cells.

Transmembrane channel-like protein 1 (TMC1) is a transmembrane protein forming mechano-electrical transduction (MET) channel, which transduces mechanical stimuli into electrical signals at the top of stereocilia of hair cells in the inner ear. As an unexpected phenomenon, we found that the cytosolic N-terminal (Nt) region of heterologously-expressed mouse TMC1 (mTMC1) was localized in nuclei of a small population of the transfected HEK293 cells. This raised the possibility that the Nt region of heterologously-expressed mTMC1 was cleaved and transported into the nucleus. To confirm the cleavage, we performed western blot analyses. The results revealed that at least a fragment of the Nt region was produced from heterologously-expressed mTMC1. Site-directed mutagenesis experiments identified amino acid residues which were required to produce the fragment. The accumulation of the heterologously-expressed Nt fragment into the nuclei depended on nuclear localization signals within the Nt region. Furthermore, a structural comparison showed a similarity between the Nt region of mTMC1 and basic region leucine zipper (bZIP) transcription factors. However, transcriptome analyses using a next-generation sequencer showed that the heterologously-expression of the Nt fragment of mTMC1 hardly altered expression levels of genes. Although it is still unknown what is the precise mechanism and the physiological significance of this cleavage, these results showed that the cytosolic Nt region of heterologously-expressed mTMC1 could be cleaved in HEK293 cells. Therefore, it should be taken into account that the cleavage of Nt region might influence the functional analysis of TMC1 by the heterologous-expression system using HEK293 cells.

Overexpression of the Brassica rapa bZIP Transcription Factor, BrbZIP-S, Increases the Stress Tolerance in Nicotiana benthamiana.

In higher plants, S1-basic region-leucine zipper (S1-bZIP) transcription factors fulfill crucial roles in the physiological homeostasis of carbon and amino acid metabolisms and stress responses. However, very little is known about the physiological role of S1-bZIP in cruciferous vegetables. Here, we analyzed the physiological function of S1-bZIP from Brassica rapa (BrbZIP-S) in modulating proline and sugar metabolism. Overexpression of BrbZIP-S in Nicotiana benthamiana resulted in delayed chlorophyll degradation during the response to dark conditions. Under heat stress or recovery conditions, the transgenic lines exhibited a lower accumulation of H2O2, malondialdehyde, and protein carbonyls compared to the levels in transgenic control plants. These results strongly indicate that BrbZIP-S regulates plant tolerance against dark and heat stress. We propose that BrbZIP-S is a modulator of proline and sugar metabolism, which are required for energy homeostasis in response to environmental stress conditions.

Protections of transcription factor BACH2 and natural product myricetin against pathological cardiac hypertrophy and dysfunction.

Pathological hypertrophic myocardium under consistent adverse stimuli eventually can cause heart failure. This study aims to explore the role of BACH2, a member of the basic region leucine zipper transcription factor family, in cardiac hypertrophy and failure. Transverse aortic constriction surgery was operated to induce cardiac hypertrophy and failure in mice. BACH2 was overexpressed in mice through tail vein injection of AAV9-Bach2. Mice with systemic or cardiac-specific knockdown of Bach2 were adopted. Neonatal rat ventricular myocytes (NRVMs) were isolated and infected with lentivirus to overexpress Bach2 or transfected with siRNA to knock down Bach2. Our data showed that overexpression of BACH2 ameliorated TAC-induced cardiac hypertrophy and failure in mice and decreased isoproterenol (ISO)-triggered myocyte hypertrophy in NRVMs. Systemic or cardiac-specific knockdown of Bach2 worsened the cardiac hypertrophy and failure phenotype in mice. Further assays showed that BACH2 bound to the promotor region of Akap6 at the -600 to -587 site and repressed its expression, which functioned as a crucial scaffold for cardiac hypertrophy and failure signaling pathways. Small molecular natural product library screening suggested that myricetin could up-regulate expression of Bach2 and simultaneously suppress the transcriptional levels of hypertrophic marker genes Bnp and Myh7. Further studies showed that myricetin exerted a BACH2-dependent protective effect against cardiac hypertrophy in vivo and in vitro. Taken together, our findings demonstrated that BACH2 plays a crucial role in the regulation of cardiac hypertrophy and failure and can be a potential therapeutic target in the future.

Advancements in Activating Transcription Factor 5 Function in Regulating Cell Stress and Survival.

Activating transcription factor 5 (ATF5) belongs to the activating transcription factor/cyclic adenosine monophosphate (cAMP) response element-binding protein family of basic region leucine zipper transcription factors. ATF5 plays an important role in cell stress regulation and is involved in cell differentiation and survival, as well as centrosome maintenance and development. Accumulating evidence demonstrates that ATF5 plays an oncogenic role in cancer by regulating gene expressions involved in tumorigenesis and tumor survival. Recent studies have indicated that ATF5 may also modify the gene expressions involved in other diseases. This review explores in detail the regulation of ATF5 expression and signaling pathways and elucidates the role of ATF5 in cancer biology. Furthermore, an overview of putative therapeutic strategies that can be used for restoring aberrant ATF5 activity in different cancer types is provided.

The Effects of Nuclear Factor Erythroid 2 (NFE2)-Related Factor 2 (Nrf2) Activation in Preclinical Models of Peripheral Neuropathic Pain.

Oxidative stress, resulting from an imbalance between the formation of damaging free radicals and availability of protective antioxidants, can contribute to peripheral neuropathic pain conditions. Reactive oxygen and nitrogen species, as well as products of the mitochondrial metabolism such as superoxide anions, hydrogen peroxide, and hydroxyl radicals, are common free radicals. Nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2) is a transcription factor encoded by the NFE2L2 gene and is a member of the cap ‘n’ collar subfamily of basic region leucine zipper transcription factors. Under normal physiological conditions, Nrf2 remains bound to Kelch-like ECH-associated protein 1 in the cytoplasm that ultimately leads to proteasomal degradation. During peripheral neuropathy, Nrf2 can translocate to the nucleus, where it heterodimerizes with muscle aponeurosis fibromatosis proteins and binds to antioxidant response elements (AREs). It is becoming increasingly clear that the Nrf2 interaction with ARE leads to the transcription of several antioxidative enzymes that can ameliorate neuropathy and neuropathic pain in rodent models. Current evidence indicates that the antinociceptive effects of Nrf2 occur via reducing oxidative stress, neuroinflammation, and mitochondrial dysfunction. Here, we will summarize the preclinical evidence supporting the role of Nrf2 signaling pathways and Nrf2 inducers in alleviating peripheral neuropathic pain.

MiR2105 and the kinase OsSAPK10 co-regulate OsbZIP86 to mediate drought-induced ABA biosynthesis in rice.

Mediating induced abscisic acid (ABA) biosynthesis is important for enhancing plant stress tolerance. Here, we found that rice (Oryza sativa L.) osa-miR2105 (miR2105) and the Stress/ABA-activated protein kinase (OsSAPK10) coordinately regulate the rice basic region-leucine zipper transcription factor (bZIP TF; OsbZIP86) at the posttranscriptional and posttranslational levels to control drought-induced ABA biosynthesis via modulation of rice 9-cis-epoxycarotenoid dioxygenase (OsNCED3) expression. OsbZIP86 expression is regulated by miR2105-directed cleavage of the OsbZIP86 mRNA. OsbZIP86 encodes a nuclear TF that binds to the promoter of the ABA biosynthetic gene OsNCED3. OsSAPK10 can phosphorylate and activate OsbZIP86 to enhance the expression of OsNCED3. Under normal growth conditions, altered expression of miR2105 and OsbZIP86 displayed no substantial effect on rice growth. However, under drought conditions, miR2105 knockdown or OsbZIP86 overexpression transgenic rice plants showed higher ABA content, enhanced tolerance to drought, lower rates of water loss, and more stomatal closure of seedlings, compared with wild-type rice Zhonghua 11; in contrast, miR2105 overexpression, OsbZIP86 downregulation, and OsbZIP86 knockout plants displayed opposite phenotypes. Collectively, our results show that the "miR2105-(OsSAPK10)-OsbZIP86-OsNCED3" module regulates the drought-induced ABA biosynthesis without penalty on rice growth under normal conditions, suggesting candidates for improving drought tolerance in rice.

Characterization and functional study of nuclear factor erythroid 2-related factor 2 (Nrf2) in black tiger shrimp (Penaeus monodon)

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a member of the Cap'n′collar basic region leucine zipper (CNC-bZIP) transcription factor family, and is activated by diverse oxidants, pro-oxidants, antioxidants and chemopreventive agents. The full-length cDNA of Nrf2 from Penaeus monodon (PmNrf2; 2024 bp long with 729 bp coding region, GenBank accession no. MW390830) was cloned. The 242-amino-acid polypeptide encoded by this gene had a predicted molecular mass of 27.80 kDa. Sequence homology and phylogenetic analysis showed that PmNrf2 was similar to the insect Cap'n′Collar (CNC) transcription factor and mammalian Nrf2. Tissue expression profile analyzed by quantitative real-time RT-PCR (qRT-PCR) demonstrated that PmNrf2 was constitutively expressed in all examined tissues, with the highest expression observed in the intestines and the weakest expression observed in the hemocyte. PmNrf2 expression profiles were detected in the hepatopancreas of shrimp after bacterial challenge. The results suggested that PmNrf2 was involved in the responses to bacterial challenge, but the temporal expression pattern trend of PmNrf2 differed between the gram-negative and gram-positive bacterial challenges in the shrimp hepatopancreas. The recombinant PmNrf2 protein was expressed and purified through affinity chromatography. Furthermore, an anti-PmNrf2 polyclonal antibody was obtained, which was able to clearly detect PmNrf2 protein expression in the hepatopancreas of shrimp. Knockdown of PmNrf2 by RNA interference (RNAi) resulted in a reduction in the expression of PmGPx gene. Taken together, the results of our study indicated that PmNrf2 played a role in regulation the transcription of PmGPx antioxidant enzyme genes.

Genome-wide investigation of the bZIP transcription factor gene family in Prunus mume: Classification, evolution, expression profile and low-temperature stress responses

Prunus mume is an important woody plant that has high ornamental and economic value, widely distributed and used in landscape architecture in East Asia. In plants, basic (region) leucine zipper (bZIP) transcription factors play important regulatory roles in growth, development, dormancy and abiotic stress. To date, bZIP transcription factors have not been systematically studied in P. mume. In this study, 49 bZIP genes were first identified in P. mume, and the PmbZIP family was divided into 12 groups according to the grouping principles for the Arabidopsis thaliana bZIP family. For the first time, we constructed a detailed model of the PmbZIP domains (R-x3N-x7-R/K-x2-K-x6-L-x6-L-x6-L). Phylogenetic and synteny analyses showed that PmbZIPs duplication events might have occurred during the large-scale genome duplication events. A relatively short time of speciation and the finding that 91.84% of the bZIP genes formed orthologous pairs between P. mume and Prunus armeniaca provided evidence of a close relationship. Gene expression patterns were analysed in different tissues and periods, indicating that PmbZIP genes with the same motifs exhibited similar expression patterns. The gene expression results showed that PmbZIP31/36/41 genes played a more prominent role in the response to freezing stress than cold stress. The expression level of almost all subset III genes was upregulated under freezing treatment, especially after cold exposure. We analysed the gene expression patterns of PmbZIP12/31/36/41/48 and their responses to low-temperature stress, which provided useful resources for future studies on the cold/freezing-tolerant molecular breeding of P. mume.

Genome-wide analysis of the bZIP gene family and the role of AchnABF1 from postharvest kiwifruit (Actinidia chinensis cv. Hongyang) in osmotic and freezing stress adaptations

Chilling injury (CI) is a barrier to the refrigeration of kiwifruit, resulting in decreased fruit quality and increased nutrient loss during storage. Understanding the molecular basis underlying the cold response and its regulation in refrigerated kiwifruit is therefore highly important. Basic (region) leucine zipper (bZIP) transcription factors (TFs) have been widely studied for their roles in abiotic stress resistance in various species. In this study, we identified 81 bZIP family proteins in kiwifruit and classified them into 11 groups. Further transcriptome analysis revealed that the expression of members of the AREB/ABF family was strongly induced by low temperature and abscisic acid (ABA). Ectopic expression of AchnABF1 enhanced plant cold tolerance by upregulating the expression of several key genes associated with ABA-dependent and ABA-independent pathways in Arabidopsis thaliana. Reactive oxygen species (ROS) metabolism was suggested to be involved in the AchnABF1-mediated osmotic stress response. For instance, enhanced ROS-scavenging ability was observed in transgenic plants with enhanced activity of catalase (CAT) and peroxidase (POD), which resulted in decreased in situ O2.− and H2O2 accumulation, ion leakage, and malondialdehyde (MDA) content under various abiotic stresses. In addition, AchnABF1 also participated in the osmotic stress response during both the germination and postgermination stages. We concluded that AchnABF1 may play an important role in kiwifruit during refrigeration.

Insight into the bZIP Gene Family in Solanum tuberosum: Genome and Transcriptome Analysis to Understand the Roles of Gene Diversification in Spatiotemporal Gene Expression and Function.

The basic region-leucine zipper (bZIP) transcription factors (TFs) form homodimers and heterodimers via the coil–coil region. The bZIP dimerization network influences gene expression across plant development and in response to a range of environmental stresses. The recent release of the most comprehensive potato reference genome was used to identify 80 StbZIP genes and to characterize their gene structure, phylogenetic relationships, and gene expression profiles. The StbZIP genes have undergone 22 segmental and one tandem duplication events. Ka/Ks analysis suggested that most duplications experienced purifying selection. Amino acid sequence alignments and phylogenetic comparisons made with the Arabidopsis bZIP family were used to assign the StbZIP genes to functional groups based on the Arabidopsis orthologs. The patterns of introns and exons were conserved within the assigned functional groups which are supportive of the phylogeny and evidence of a common progenitor. Inspection of the leucine repeat heptads within the bZIP domains identified a pattern of attractive pairs favoring homodimerization, and repulsive pairs favoring heterodimerization. These patterns of attractive and repulsive heptads were similar within each functional group for Arabidopsis and S. tuberosum orthologs. High-throughput RNA-seq data indicated the most highly expressed and repressed genes that might play significant roles in tissue growth and development, abiotic stress response, and response to pathogens including Potato virus X. These data provide useful information for further functional analysis of the StbZIP gene family and their potential applications in crop improvement.

Characterization of the Cap 'n' Collar Isoform C gene in Spodoptera frugiperda and its Association with Superoxide Dismutase.

Nuclear factor erythroid 2 related factor 2 (Nrf2) belongs to the cap ‘n’ collar basic region leucine zipper (CNC-bZIP) transcription factor family, and is activated by diverse oxidants, pro-oxidants, antioxidants, and chemo-preventive agents. Transcriptional regulation of a battery of detoxifying and antioxidant genes by Nrf2 has been shown to be important for protection against oxidative stress or chemically-induced cellular damages. In our research, we cloned the full length CncC gene from the Spodoptera frugiperda, named as SfCncC. The cDNA of the SfCncC consists of 2652 nucleotides that include a 2196-nucleotide open reading frame (ORF), encoding 731 amino acid residues, and 239- and 217-bp non-coding regions flanking at the 5’- and 3’-ends of the cDNA, respectively. Sequence analysis indicated SfCncC has the conserved domain (CNC-bZIP domain and a tetrapeptide motif, ETGE) character of Nrf2 and showed high identity compared with the CncC/Nrf2 from other insect and vertebrate species. Over-expression of SfCncC can up-regulate the transcription and activity of the SOD gene in Sf9 cells, and the RNAi of SfCncC in Sf9 cells and larvae of S. frugiperda can dramatically reduce the transcriptional level and activity of the SOD gene, as determined by real-time quantitative PCRs. So the SfCncC is involved in the Keap1-Nrf2-ARE pathway, acting the same as the transcriptional factor Nrf2 in vertebrate, and plays a role for host cell defense. The functional characterization of SfCncC provides the fundamental basis for us to further understand the regulatory mechanism of anti-oxidants and anti-xenobiotics in S. frugiperda.

TOX and TOX2 transcription factors cooperate with NR4A transcription factors to impose CD8+ T cell exhaustion

T cells expressing chimeric antigen receptors (CAR T cells) have shown impressive therapeutic efficacy against leukemias and lymphomas. However, they have not been as effective against solid tumors because they become hyporesponsive ("exhausted" or "dysfunctional") within the tumor microenvironment, with decreased cytokine production and increased expression of several inhibitory surface receptors. Here we define a transcriptional network that mediates CD8+ T cell exhaustion. We show that the high-mobility group (HMG)-box transcription factors TOX and TOX2, as well as members of the NR4A family of nuclear receptors, are targets of the calcium/calcineurin-regulated transcription factor NFAT, even in the absence of its partner AP-1 (FOS-JUN). Using a previously established CAR T cell model, we show that TOX and TOX2 are highly induced in CD8+ CAR+ PD-1high TIM3high ("exhausted") tumor-infiltrating lymphocytes (CAR TILs), and CAR TILs deficient in both TOX and TOX2 (Tox DKO) are more effective than wild-type (WT), TOX-deficient, or TOX2-deficient CAR TILs in suppressing tumor growth and prolonging survival of tumor-bearing mice. Like NR4A-deficient CAR TILs, Tox DKO CAR TILs show increased cytokine expression, decreased expression of inhibitory receptors, and increased accessibility of regions enriched for motifs that bind activation-associated nuclear factor κB (NFκB) and basic region-leucine zipper (bZIP) transcription factors. These data indicate that Tox and Nr4a transcription factors are critical for the transcriptional program of CD8+ T cell exhaustion downstream of NFAT. We provide evidence for positive regulation of NR4A by TOX and of TOX by NR4A, and suggest that disruption of TOX and NR4A expression or activity could be promising strategies for cancer immunotherapy.

TET enzymes augment AID expression via 5hmC modifications at the Aicda superenhancer

Abstract TET enzymes are dioxygenases that promote DNA demethylation by oxidizing the methyl group of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). Here we report a close correspondence between 5hmC-marked regions, chromatin accessibility and enhancer activity in B cells, and a strong enrichment for consensus binding motifs for basic region-leucine zipper (bZIP) transcription factors at TET-responsive genomic regions. Functionally, Tet2 and Tet3 regulate class switch recombination (CSR) in murine B cells by enhancing expression of Aicda, encoding the cytidine deaminase AID essential for CSR. TET enzymes deposit 5hmC, demethylate and maintain chromatin accessibility at two TET-responsive elements, TetE1 and TetE2, located within a superenhancer in the Aicda locus. Our data identify BATF as a key bZIP transcription factor involved in TET-dependent Aicda expression. 5hmC is not deposited at TetE1 in activated Batf-deficient B cells, indicating that BATF facilitates TET recruitment to this Aicda enhancer. Our study emphasizes the importance of TET enzymes for bolstering AID expression, and highlight 5hmC as an epigenetic mark that captures enhancer dynamics during cell activation.