Leucine Zipper Protein Research Articles

The Potential Role of bZIP55/65 in Nitrogen Uptake and Utilization in Cucumber Is Revealed via bZIP Gene Family Characterization.

The bZIP (basic leucine zipper) proteins play crucial roles in various biological functions. Nitrogen (N) is an essential element for plant growth, especially in cucumber (Cucumis sativus) due to its shallow roots. However, the regulation of bZIP genes in cucumber nitrogen metabolism has not been studied yet. In this study, we identified a total of 72 bZIP genes (CsbZIPs) in the cucumber genome that could be classified into 13 groups. These genes were unevenly distributed on seven chromosomes, and synteny analysis showed that the CsbZIP genes were expanded in a segmentally duplicating manner. Furthermore, our genome-wide expression analysis suggested that CsbZIP genes had different patterns and that five CsbZIP genes were regulated by nitrogen treatment in both leaves and roots. Consistent with CsNPF, CsbZIP55 and CsbZIP65 were regulated by nitrogen treatment in leaves and roots. Moreover, the subcellular localization showed that CsbZIP55 and CsbZIP65 were specifically located in the nucleus, and the transcriptional activation assay showed that CsbZIP55 and CsbZIP65 have transcriptional activation activity. Additionally, in the CsbZIP55 and CsbZIP65 overexpression plants, most nitrogen-regulated CsNPF genes were downregulated. Taken together, our comprehensive analysis of the bZIP gene family lays a foundation for understanding the molecular and physiological functions of CsbZIPs.

Glucocorticoid dysfunction in children with severe malaria.

Malaria remains a widespread health problem with a huge burden. Severe or complicated malaria is highly lethal and encompasses a variety of pathological processes, including immune activation, inflammation, and dysmetabolism. Previously, we showed that adrenal hormones, in particular glucocorticoids (GCs), play critical roles to maintain disease tolerance during Plasmodium infection in mice. Here, GC responses were studied in Cameroon in children with uncomplicated malaria (UM), severe malaria (SM) and asymptomatic controls (AC). To determine the sensitivity of leukocytes to GC signaling on a transcriptional level, we measured the ex vivo induction of glucocorticoid induced leucine zipper (GILZ) and FK506-binding protein 5 (FKBP5) by GCs in human and murine leukocytes. Targeted tracer metabolomics on peripheral blood mononuclear cells (PBMCs) was performed to detect metabolic changes induced by GCs. Total cortisol levels increased in patients with clinical malaria compared to AC and were higher in the SM versus UM group, while cortisol binding globulin levels were unchanged and adrenocorticotropic hormone (ACTH) levels were heterogeneous. Induction of both GILZ and FKBP5 by GCs was significantly reduced in patients with clinical malaria compared to AC and in malaria-infected mice compared to uninfected controls. Increased activity in the pentose phosphate pathway was found in the patients, but this was not affected by ex vivo stimulation with physiological levels of hydrocortisone. Interestingly, hydrocortisone induced increased levels of cAMP in AC, but not in clinical malaria patients. Altogether, this study shows that patients with SM have increased cortisol levels, but also a decreased sensitivity to GCs, which may clearly contribute to the severity of disease.

The role of walnut bZIP genes in explant browning

BackgroundBasic leucine zipper (bZIP) proteins are important transcription factors in plants. To study the role of bZIP transcription factors in walnut explant browning, this study used bioinformatics software to analyze walnut bZIP gene family members, along with their transcript levels in different walnut tissues, to evaluate the transcriptional expression of this gene family during the primary culture of walnut explants and to reveal the mechanism of action of walnut bZIP genes in walnut explant browning.ResultsThe results identified 65 JrbZIP genes in the walnut genome, which were divided into 8 subfamilies and distributed on 16 chromosomes. The results of transcriptome data analysis showed that there were significant differences in the expression of four genes, namely, JrbZIP55, JrbZIP70, JrbZIP72, and JrbZIP88, under both vermiculite and agar culture conditions. There were multiple hormone (salicylic acid, abscisic acid, auxin, and gibberellin) signaling and regulatory elements that are responsive to stress (low temperature, stress, and defense) located in the promoter regions of JrbZIP55, JrbZIP70, JrbZIP72, and JrbZIP88. The walnut JrbZIP55 protein and Arabidopsis bZIP42 protein are highly homologous, and the proteins interacting with Arabidopsis bZIP42 include the AT2G19940 oxidoreductases, which act on aldehyde or oxygen-containing donors.ConclusionIt is speculated that JrbZIP55 may participate in the regulation of browning in walnut explants.

Transcription factors TgbHLH95 and TgbZIP44 co-target terpene biosynthesis gene TgGPPS in Torreya grandis nuts.

Terpenes are volatile compounds responsible for aroma and the postharvest quality of commercially important xiangfei (Torreya grandis) nuts, and there is interest in understanding the regulation of their biosynthesis. Here, a transcriptomics analysis of xiangfei nuts after harvest identified 156 genes associated with the terpenoid metabolic pathway. A geranyl diphosphate (GPP) synthase (TgGPPS) involved in production of the monoterpene precursor GPP was targeted for functional characterization, and its transcript levels positively correlated with terpene levels. Furthermore, transient overexpression of TgGPPS in tobacco (Nicotiana tabacum) leaves or tomato (Solanum lycopersicum) fruit led to monoterpene accumulation. Analysis of differentially expressed transcription factors identified one basic helix-loop-helix protein (TgbHLH95) and one basic leucine zipper protein (TgbZIP44) as potential TgGPPS regulators. TgbHLH95 showed significant transactivation of the TgGPPS promoter, and its transient overexpression in tobacco leaves led to monoterpene accumulation, whereas TgbZIP44 directly bound to an ACGT-containing element in the TgGPPS promoter, as determined by yeast one-hybrid test and electrophoretic mobility shift assay. Bimolecular fluorescence complementation, firefly luciferase complementation imaging, co-immunoprecipitation and GST pull-down assays confirmed a direct protein-protein interaction between TgbHLH95 and TgbZIP44 in vivo and in vitro, and in combination these proteins induced the TgGPPS promoter up to 4.7-fold in transactivation assays. These results indicate that a TgbHLH95/TgbZIP44 complex activates the TgGPPS promoter and up-regulates terpene biosynthesis in xiangfei nuts after harvest, thereby contributing to its aroma.

Leucine zipper protein 1 prevents doxorubicin-induced cardiotoxicity in mice

ObjectiveDoxorubicin (DOX) is commonly used for chemotherapy; however, its clinical value is extremely dampened because of the fatal cardiotoxicity. Leucine zipper protein 1 (LUZP1) plays critical roles in cardiovascular development, and this study is designed for determining its function and mechanism in DOX-induced cardiotoxicity. MethodsCardiac-specific Luzp1 knockout (cKO) and transgenic (cTG) mice received a single or repeated DOX injections to establish acute and chronic cardiotoxicity. Biomarkers of inflammation, oxidative damage and cell apoptosis were evaluated. Transcriptome and co-immunoprecipitation analysis were used to screen the underlying molecular pathways. Meanwhile, primary cardiomyocytes were applied to confirm the beneficial effects of LUZP1 in depth. ResultsLUZP1 was upregulated in DOX-injured hearts and cardiomyocytes. Cardiac-specific LUZP1 deficiency aggravated, while cardiac-specific LUZP1 overexpression attenuated DOX-associated inflammation, oxidative damage, cell apoptosis and acute cardiac injury. Mechanistic studies revealed that LUZP1 ameliorated DOX-induced cardiotoxicity through activating 5′-AMP-activated protein kinase (AMPK) pathway, and AMPK deficiency abolished the cardioprotection of LUZP1. Further findings suggested that LUZP1 interacted with protein phosphatase 1 to activate AMPK pathway. Moreover, we determined that cardiac-specific LUZP1 overexpression could also attenuate DOX-associated chronic cardiac injury in mice. ConclusionLUZP1 attenuates DOX-induced inflammation, oxidative damage, cell apoptosis and ventricular impairment through regulating AMPK pathway, and gene therapy targeting LUZP1 may provide novel therapeutic approached to treat DOX-induced cardiotoxicity.

Integrative analysis of exogenous auxin mediated plant height regulation in Moso bamboo (Phyllostachys edulis)

Auxin is important in regulating bamboo growth and development. Morphological and anatomical analyses of naturally growing Moso bamboo treated with auxin revealed that auxin-mediated regulation of bamboo height mainly increased internode length rather than nodes number. For individual internodes, auxin regulated internode elongation mainly by promoting cell elongation. Targeted metabolomic assays of endogenous hormones found that exogenous auxin treatment affected the dynamic balance of endogenous hormones, resulting in increased levels of gibberellin and cytokinin. Transcriptome sequencing indicated that the regulation of internode length by auxin is mainly through phytohormone signaling pathway, amino acid synthesis and protein processing pathway, and energy metabolism pathway. The transcription factors that play major regulatory roles included the ethylene response factor, WRKY and MYB transcription factor, NAC structural domain protein and basic leucine zipper protein. By constructing a gene regulatory network, we found that auxin may crosstalk with multiple plant hormones. Yeast two-hybrid and transgenic experiments demonstrated that the auxin signaling factor PheAUX/IAA34 and the jasmonic acid signaling factor PheTIFY28 do interact and regulate growth in response to phytohormones. Overall we have obtained good quality bamboo internode material for industry through the auxin treatment and have preliminarily investigated the mechanism, which will provide a reference for bamboo plant height regulation.

Small heterodimer partner interacting leucine zipper protein (SMILE) ameliorates autoimmune arthritis via AMPK signaling pathway and the regulation of B cell activation

Rheumatoid arthritis (RA) is an autoimmune disease that causes joint swelling and inflammation and can involve the entire body. RA is characterized by the increase of pro-inflammatory cytokines such as interleukin (IL) and tumor necrosis factor, and the over-activation of T lymphocytes and B lymphocytes, which may lead to severe chronic inflammation of joints. However, despite numerous studies the pathogenesis and treatment of RA remain unresolved. This study investigated the use of small heterodimer partner-interacting leucine zipper protein (SMILE) overexpression to treat a mouse model of RA. SMILE is an insulin-inducible corepressor through adenosine monophosphate-activated kinase (AMPK) signaling pathway. The injection of a SMILE overexpression vector to mice with collagen induced-arthritis resulted in a milder clinical pathology and a reduced incidence of arthritis, less joint tissue damage, and lower levels of Th17 cells and plasma B cells in the spleen. Immunohistochemistry of the joint tissue showed that SMILE decreased B-cell activating factor (BAFF) receptor (BAFF-R), mTOR, and STAT3 expression but increased AMPK expression. In SMILE-overexpressing transgenic mice with collagen antibody-induced arthritis (CAIA), a decrease in the arthritis score and reductions in tissue damage, the number of B cells, and antibody production were observed. The treatment of immune cells in vitro with curcumin, a known SMILE-inducing agent, led to decreases in plasma B cells, germinal center B cells, IL-17-producing B cells, and BAFF-R-positive B cells. Taken together, our findings demonstrate the therapeutic potential of SMILE in RA, based on its inhibition of B cell activation mediated by the AMPK/mTOR and STAT3 signaling pathway and BAFF-R expression.EtcT49u9cQiSZwStZ5UX76Video abstract

HD-ZIP III-dependent local promotion of brassinosteroid synthesis suppresses vascular cell division in Arabidopsis root apical meristem

Spatiotemporal control of cell division in the meristem is vital for plant growth. In the stele of the root apical meristem (RAM), procambial cells divide periclinally to increase the number of vascular cell files. Class III homeodomain leucine zipper (HD-ZIP III) proteins are key transcriptional regulators of RAM development and suppress the periclinal division of vascular cells in the stele; however, the mechanism underlying the regulation of vascular cell division by HD-ZIP III transcription factors (TFs) remains largely unknown. Here, we performed transcriptome analysis to identify downstream genes of HD-ZIP III and found that HD-ZIP III TFs positively regulate brassinosteroid biosynthesis-related genes, such as CONSTITUTIVE PHOTOMORPHOGENIC DWARF (CPD), in vascular cells. Introduction of pREVOLUTA::CPD in a quadruple loss-of-function mutant of HD-ZIP III genes partly rescued the phenotype in terms of the vascular defect in the RAM. Treatment of a quadruple loss-of-function mutant, a gain-of-function mutant of HD-ZIP III, and the wild type with brassinosteroid and a brassinosteroid synthesis inhibitor also indicated that HD-ZIP III TFs act together to suppress vascular cell division by increasing brassinosteroid levels. Furthermore, brassinosteroid application suppressed the cytokinin response in vascular cells. Together, our findings suggest that the suppression of vascular cell division by HD-ZIP III TFs is caused, at least in part, by the increase in brassinosteroid levels through the transcriptional activation of brassinosteroid biosynthesis genes in the vascular cells of the RAM. This elevated brassinosteroid level suppresses cytokinin response in vascular cells, inhibiting vascular cell division in the RAM.

JLP/Foxk1/N-cadherin axis fosters a partial epithelial-mesenchymal transition state in epithelial tubular cells

Renal tubular epithelial cells (TECs) undergoing partial epithelial-mesenchymal transition (pEMT) during renal fibrosis has been recognized as a featuring and detrimental event. However, the mechanism for redirecting the cell fate of pEMT remains unclear. Here we mapped the temporal expression trajectories of a series of EMT-related molecules in renal fibrosis. It revealed a unique expression profile of N-cadherin of initial rising and late dropdown, which is distinct from that of other mesenchymal markers. The transcription factor Foxk1, which serves as a negative regulator of the N-cadherin gene, was induced by TGF-β1 but was tightly regulated in the presence of JNK-associated leucine zipper protein (JLP). The loss of JLP resulted in Foxk1 induction, leading to N-cadherin downregulation and compromised cell viability. We propose a novel axis consisting of JLP/Foxk1/N-cadherin in shaping the EMT program and suggest JLP as the checkpoint of the EMT continuum during renal fibrosis progression.

Global analysis of basic leucine zipper transcription factors in trifoliate orange and the function identification of PtbZIP49 in salt tolerance

As one of the most widely distributed and highly conserved transcription factors in eukaryotes, basic leucine zipper proteins (bZIPs) are involved in a variety of biological processes in plants, but they are largely unknown in citrus. In this study, 56 bZIP family members were identified genome-wide from an important citrus rootstock, namely trifoliate orange (Poncirus trifoliata L. Raf.), and these putative bZIPs were named PtbZIP1–PtbZIP56. All PtbZIPs were classified into 13 subgroups by phylogenetic comparison with Arabidopsis thaliana bZIPs (AtbZIPs), and they were randomly distributed on nine known (50 genes) chromosomes and one unknown (6 genes) chromosome. Sequence analysis revealed the detailed characteristics of PtPZIPs, including their amino acid length, isoelectric point (pI), molecular weight (MW), predicted subcellular localization, gene structure, and conserved motifs. Prediction of promoter elements suggested the presence of drought, low-temperature, wound, and defense and stress responsive elements, as well as multiple hormone-responsive cis-acting elements. Spatiotemporal expression analysis showed the transcriptional patterns of PtbZIPs in different tissues and under dehydration, high salt, ABA, and IAA treatments. In addition, 21 PtbZIPs were predicted to have direct or indirect protein–protein interactions. Among these, PtbZIP49 was experimentally proven to interact with PtbZIP1 or PtbZIP11 by using a yeast two-hybrid assay and bimolecular fluorescence complementation (BiFC). Subcellular localization analysis further revealed that PtbZIP1, PtbZIP11, and PtbZIP49 were localized in the nucleus. Moreover, PtbZIP49 was functionally identified as having an important role in salt stress via ectopic expression in A. thaliana and silenced in trifoliate orange using virus-induced gene silencing (VIGS). This study provided comprehensive information on PtbZIP transcription factors in citrus and highlights their potential functions in abiotic stress.

Genome-Wide Identification of Homeodomain Leucine Zipper (HD-ZIP) Transcription Factor, Expression Analysis, and Protein Interaction of HD-ZIP IV in Oil Palm Somatic Embryogenesis

Understanding the molecular mechanisms underlying somatic embryogenesis is essential for resolving the problems related to the long duration of the process and a low rate of somatic embryo induction in oil palm tissue culture. In this study, we conducted genome-wide identification of the oil palm homeodomain leucine zipper (EgHD-ZIP) family, which is one of the plant-specific transcription factors reported to be involved in embryogenesis. EgHD-ZIP proteins can be divided into four subfamilies, which have similarities in gene structure and protein-conserved motifs within a group. In silico expression analysis showed that the expression of EgHD-ZIP gene members in the EgHD-ZIP I and II families, as well as most members in the EgHD-ZIP IV family, were up-regulated during the zygotic and somatic embryo developmental stages. In contrast, the expression of EgHD-ZIP gene members in the EgHD-ZIP III family was down-regulated during zygotic embryo development. Moreover, the expression of EgHD-ZIP IV genes was validated in the oil palm callus and at the somatic embryo stages (globular, torpedo, and cotyledon). The results revealed that EgHD-ZIP IV genes were up-regulated at the late stages of somatic embryogenesis (torpedo and cotyledon). While BABY BOOM (BBM) gene was up-regulated at the early stage of somatic embryogenesis (globular). In addition, the Yeast-two hybrid assay revealed the direct binding between all members of the oil palm HD-ZIP IV subfamily (EgROC2, EgROC3, EgROC5, EgROC8, and EgBBM). Our findings suggested that the EgHD-ZIP IV subfamily and EgBBM work together to regulate somatic embryogenesis in oil palms. This process is important because it is widely used in plant biotechnology to produce large quantities of genetically identical plants, which can be used for oil palm tissue culture improvement.

Abstract PD5-05: PD5-05 DAPK3 modulates migration and invasion of triple negative breast cancers

Abstract Triple negative breast cancer (TNBC) is associated with poorer prognosis compared to other subtypes of breast cancer due to aggressive metastatic behavior and lack of targeted therapies. Human kinases are a large family of proteins that play critical roles in multiple biological pathways, and aberrant expression or mutations of kinases drive cancer progression and metastasis. Therefore, we applied Mass Spectrometry (MS)-based Kinase-inhibitor pulldown (KiP) technology to profile unique kinase signatures associated with TNBC and prioritize novel regulators for this subtype. Human kinases were captured by a mixture of nine FDA-approved kinase inhibitors, each conjugated separately to sepharose beads to profile all the major branches of the kinome tree. We performed KiP assay in 16 patient-derived xenografts (PDXs) [PMC5379071] consisting of different molecular subtypes of breast cancers. Differential expression analysis identified Death Associated Protein Kinase 3 (DAPK3) as a significantly upregulated kinase in TNBC PDXs which somehow remains understudied. Furthermore, RNA-seq and proteomics data with the same set of PDXs revealed that the upregulation of DAPK3 expression in TNBC was exclusively at protein levels, not RNA levels. Consistently, DAPK3 protein levels were significantly elevated in TNBC cell lines in DepMap dataset. Genomic knockout of DAPK3 in SUM159 and MDA-MB-231 cells dramatically inhibited migration and invasion measured by the transwell assay. We also observed that DAPK3 knockout reduced the phosphorylation of Myosin Light Chain 2 (MLC2) at T18/S19 site, which was shown to regulate cancer cell invasion [PMC4195943]. DAPK3 belong to DAPK family protein, and has an N-terminus kinase domain with high homology to its family proteins, and a C-terminus leucine-zipper domain. While re-expression of wild-type (WT) DAPK3 cDNA can rescue the migration and invasion phenotype caused by DAPK3 knockout, kinase-dead mutant (D161N) and leucine-zipper-domain-deleted mutant (ΔLZ) cannot rescue the phenotype. Moreover, not only D161N, but also ΔLZ mutant cannot restore the phosphorylation level of MLC2 as DAPK3 WT does. Therefore, both kinase activity and leucin-zipper domain of DAPK3 are critical for the phosphorylation of its substrate MLC2 and thus migration and invasion phenotype. By unbiased Immunoprecipitation-Mass Spectrometry (IP-MS) method, we identified Leucine-Zipper Protein 1 (LUZP1) as one of the strongest interactors of DAPK3. Interestingly, LUZP1 also has a leucine-zipper domain on its N-terminus. Further study showed that DAPK3 binds to LUZP1 via its leucine-zipper domain as expected. Moreover, we observed a tight correlation between DAPK3 and LUZP1 protein expressions in the proteomics data of PDXs and DepMap cell lines (Pearson correlation coefficient is 0.90 and 0.81, respectively). However, the correlation at RNA levels is not significant. Besides, we found that DAPK3 protein stability, but not RNA, is dependent on LUZP1 presence in TNBC cells, strongly implying the roles of LUZP1 on the post-transcriptional regulation of DAPK3. To summarize, we demonstrated that DAPK3, as a novel TNBC-enriched protein, modulates migration and invasion possibly via MLC2 phosphorylation. Both kinase activity and leucine-zipper domain of DAPK3 is necessary for its functionality. We also found LUZP1 is a strong interactor and a potential regulator of DAPK3 in TNBC biology. Citation Format: Junkai Wang, Beom-Jun Kim, Meenakshi Anurag, Xin Yu, Xiaoli Qi, Jin Wang, Bing Zhang, Chonghui Cheng, Matthew Ellis. PD5-05 DAPK3 modulates migration and invasion of triple negative breast cancers [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD5-05.

The role of the glucocorticoid receptor and its impact on steroid response in moderate-severe COVID-19 patients

The effect of corticosteroid therapy in COVID-19 patients is mediated by its suppressive effect on the regulations of inflammatory response. However, its clinical outcome is often unpredictable. This study aimed to explore the role of glucocorticoid receptors in corticosteroid response in Moderate-Severe COVID-19 patients. In this cross-sectional study, we attempted to find the relationship between the expression of the glucocorticoid receptor (encoded by NR3C1), the variation of glucocorticoid receptors isoform, and the mutations of glucocorticoid receptors exon with clinical response to corticosteroids. In addition, the relationship between glucocorticoid receptors expression and the expression of IκBα (encoded by NFKBIA) and glucocorticoid-induced leucine zipper protein (GILZ; encoded by TSC22D3) as steroid pathways was also evaluated. Thirty-four COVID-19 patients were studied. Blood was drawn before and on day 5 of corticosteroid treatment. Glucocorticoid receptors expression, isoform, and mutation were determined by RNA sequencing from white blood cells. Based on the improvement of clinical and oxygen status, patients were classified into responder and non-responder groups. Of thirty-four patients, 23 (67.6%) showed excellent responses to corticosteroids, and 11 (32.4%) were non-responders. The NR3C1 gene expression was significantly higher in the responsive group at baseline and after five days of glucocorticoid treatment. Isoform variant and mutation of glucocorticoid receptors did not correlate with clinical response. The expression of IκBα and GILZ correlated positively with glucocorticoid receptors expression. This study elucidates the relationship between glucocorticoid receptor expression with therapeutic responses to corticosteroids in moderate-severe COVID-19.

PtrbZIP3 transcription factor regulates drought tolerance of Populus trichocarpa

Plant basic leucine zipper (bZIP) proteins participate in plant development and a variety of abiotic stress responses. However, their roles in response to abiotic stress in Populus are still unclear. In this study, we characterized a bZIP protein, PtrbZIP3, in Populus trichocarpa which belongs to the sub-family A. PtrbZIP3 expression was highly induced by treatment with NaCl, PEG6000, or abscisic acid (ABA). PtrbZIP3 is a nuclear protein with transcriptional activation activity. Yeast one hybrid and electrophoretic mobility shift analysis showed that PtrbZIP3 can specifically bind to abscisic acid-responsive element (ABRE) to regulate the expression of ABA-dependent genes and increase the amount of ABA in P. trichocarpa overexpressing PtrbZIP3. Under PEG-simulated drought conditions, overexpression of PtrbZIP3 increases the activities of antioxidant enzymes, scavenging of reactive oxygen species, maintains cell membrane integrity, reduces stomatal apertures and water loss, and increases proline accumulation. Thus PtrbZIP3 is a transcriptional activator that plays a role in an ABA-dependent pathway to improve osmotic tolerance in P. trichocarpa.

Phytochemicals to regulate oxidative and electrophilic stress through Nrf2 activation

Graphical abstract Abstract Intake of a variety of vegetables and fruit is found to be effective in promoting health; one of the reasons for this is activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a basic leucine zipper protein. Nrf2 is activated by chemical modification of Kelch-like ECH-associated protein 1 (Keap1), a negative regulator for this transcription factor, and specific phosphorylation of Nrf2, resulting in upregulation of its downstream gene products for antioxidant proteins, phase-II xenobiotic-metabolizing enzymes, and phase-III transporters. This type of activation plays a role in adaptive response and protection against oxidative and electrophilic stress. Multiple phytochemicals, such as curcumin, sulforaphane, and (E)-2-alkenals, have been identified as Nrf2 activators and may reduce the adverse health effects of oxidants and electrophiles. In this review, we introduce plant components that are known as Nrf2 activators and associated phytochemical-mediated reduction of risk from chemicals which cause oxidative and electrophilic stress. We also discuss the capture and inactivation of methylmercury, an electrophile, by sulfane sulfur atoms contained in garlic.

Mitochondrial genome recovery by ATFS-1 is essential for development after starvation

Nutrient availability regulates the C.elegans life cycle as well as mitochondrial physiology. Food deprivation significantly reduces mitochondrial genome (mtDNA) numbers and leads to aging-related phenotypes. Here we show that the bZIP (basic leucine zipper) protein ATFS-1, a mediator of the mitochondrial unfolded protein response (UPRmt), is required to promote growth and establish a functional germline after prolonged starvation. We find that recovery of mtDNA copy numbers and development after starvation requires mitochondrion-localized ATFS-1 but not its nuclear transcription activity. We also find that the insulin-like receptor DAF-2 functions upstream of ATFS-1 to modulate mtDNA content. We show that reducing DAF-2 activity represses ATFS-1 nuclear function while causing an increase in mtDNA content, partly mediated by mitochondrion-localized ATFS-1. Our data indicate the importance of the UPRmt in recovering mitochondrial mass and suggest that atfs-1-dependent mtDNA replication precedes mitochondrial network expansion after starvation.

SMILE Downregulation during Melanogenesis Induces MITF Transcription in B16F10 Cells.

SMILE (small heterodimer partner-interacting leucine zipper protein) is a transcriptional corepressor that potently regulates various cellular processes such as metabolism and growth in numerous tissues. However, its regulatory role in skin tissue remains uncharacterized. Here, we demonstrated that SMILE expression markedly decreased in human melanoma biopsy specimens and was inversely correlated with that of microphthalmia-associated transcription factor (MITF). During melanogenesis, α-melanocyte-stimulating hormone (α-MSH) induction of MITF was mediated by a decrease in SMILE expression in B16F10 mouse melanoma cells. Mechanistically, SMILE was regulated by α-MSH/cAMP/protein kinase A signaling and suppressed MITF promoter activity via corepressing transcriptional activity of the cAMP response element-binding protein. Moreover, SMILE overexpression significantly reduced α-MSH-induced MITF and melanogenic genes, thereby inhibiting melanin production in melanocytes. Conversely, SMILE inhibition increased the transcription of melanogenic genes and melanin contents. These results indicate that SMILE is a downstream effector of cAMP-mediated signaling and is a critical factor in the regulation of melanogenic transcription; in addition, they suggest a potential role of SMILE as a corepressor in skin pigmentation.

Protein kinase CK2 modulates the activity of Maf-family bZIP transcription factor NRL in rod photoreceptors of mammalian retina.

Maf-family basic motif leucine zipper protein NRL specifies rod photoreceptor cell fate during retinal development and, in concert with homeodomain protein CRX and other regulatory factors, controls the expression of most rod-expressed genes including the visual pigment gene Rhodopsin (Rho). Transcriptional regulatory activity of NRL is modulated by post-translational modifications, especially phosphorylation, and mutations at specific phosphosites can lead to retinal degeneration. During our studies to elucidate NRL-mediated transcriptional regulation, we identified protein kinase CK2 in NRL-enriched complexes bound to Rho promoter-enhancer regions and in NRL-enriched high molecular mass fractions from the bovine retina. The presence of CK2 in NRL complexes was confirmed by co-immunoprecipitation from developing and adult mouse retinal extracts. In vitro kinase assay and bioinformatic analysis indicated phosphorylation of NRL at Ser117 residue by CK2. Co-transfection of Csnk2a1 cDNA encoding murine CK2 with human NRL and CRX reduced the bovine Rho promoter-driven luciferase expression in HEK293 cells and mutagenesis of NRL-Ser117 residue to Ala restored the reporter gene activity. In concordance, overexpression of CK2 in the mouse retina in vivo by electroporation resulted in reduction of Rho promoter-driven DsRed reporter expression as well as the transcript level of many phototransduction genes. Thus, our studies demonstrate that CK2 can phosphorylate Ser117 of NRL. Modulation of NRL activity by CK2 suggests intricate interdependence of transcriptional and signaling pathways in maintaining rod homeostasis.

The roles of HD-ZIP proteins in plant abiotic stress tolerance.

Homeodomain leucine zipper (HD-ZIP) proteins are plant-specific transcription factors that contain a homeodomain (HD) and a leucine zipper (LZ) domain. The highly conserved HD binds specifically to DNA and the LZ mediates homodimer or heterodimer formation. HD-ZIP transcription factors control plant growth, development, and responses to abiotic stress by regulating downstream target genes and hormone regulatory pathways. HD-ZIP proteins are divided into four subclasses (I–IV) according to their sequence conservation and function. The genome-wide identification and expression profile analysis of HD-ZIP proteins in model plants such as Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) have improved our understanding of the functions of the different subclasses. In this review, we mainly summarize and discuss the roles of HD-ZIP proteins in plant response to abiotic stresses such as drought, salinity, low temperature, and harmful metals. HD-ZIP proteins mainly mediate plant stress tolerance by regulating the expression of downstream stress-related genes through abscisic acid (ABA) mediated signaling pathways, and also by regulating plant growth and development. This review provides a basis for understanding the roles of HD-ZIP proteins and potential targets for breeding abiotic stress tolerance in plants.

Seasonal differences in softening of early-harvested ‘Royal Gala’ apple fruit are correlated with at-harvest biomarkers indicative of abiotic stress responses

Softening of apple fruit depends on maturity at harvest and a range of orchard and environmental factors. We investigated seasonal effects on ‘Royal Gala’ storage performance independent of maturity and separate from potential orchard effects. In two consecutive seasons, fruit were harvested at four times: very early (H1), early (H2), commercial (H3) and late (H4), and were cold-stored at 0.5 °C for 100 d followed by a shelf-life period. In Year 1, fruit from H1 and H2 softened much less during storage than did fruit from Year 2. Later-harvested fruit (H3 and H4) did not show this seasonal difference and softened similarly in storage. A combined at-harvest transcriptomic and metabolomic study was analysed using mixOmics. Retained firmness in storage was correlated with increased abundance of transcripts indicative of abiotic stress, including those encoding universal stress protein, a drought stress protein, and several heat shock proteins and aquaporins. Greater softening in storage was correlated with higher abundance of fewer and different stress genes, and genes involved in cell wall metabolism. The data suggest that preharvest stresses experienced by the fruit have a profound effect on subsequent softening, at least in early-harvested fruit before ripening-related ethylene becomes the main driver. Ten potential at-harvest biomarkers were identified, including titratable acidity, erythritol and eight transcripts (notably Universal stress protein PHOS32-like and Homeobox leucine zipper protein HAT5-like). These could be useful for predicting the subsequent storage performance of batches of fruit.