Comprehensive Characterization of B-Box Zinc Finger Genes in Citrullus lanatus and Their Response to Hormone and Abiotic Stresses.

Plant B-BOX (BBX) zinc finger transcription factors play crucial roles in growth and development and the stress response. Although the BBX family has been characterized in various plants, systematic analysis in watermelon is still lacking. In this study, 25 watermelon ClBBX genes were identified. ClBBXs were grouped into five clades (Clade I, II, III, IV, and V) based on their conserved domains and phylogenetic relationships. Most of the ClBBXs (84%) might be localized in the nuclei or cytoplasm. The classification of ClBBXs was consistent with their gene structures. They were unevenly distributed in nine chromosomes except for Chr4 and Chr10, with the largest number of six members in Chr2. Segmental duplications were the major factor in ClBBX family expansion. Some BBXs of watermelon and Arabidopsis evolved from a common ancestor. In total, 254 hormonal and stress-responsive cis elements were discovered in ClBBX promoters. ClBBXs were differentially expressed in tissues, and the expression levels of ClBBX15 and 16 were higher in aboveground tissues than in roots, while the patterns of ClBBX21a, 21b, 21c, 28 and 30b were the opposite. With salicylic acid, methyl jasmonate and salt stress conditions, 17, 18 and 18 ClBBXs exhibited significant expression changes, respectively. In addition, many ClBBXs, including ClBBX29b, 30a and 30b, were also responsive to cold and osmotic stress. In summary, the simultaneous response of multiple ClBBXs to hormonal or abiotic stress suggests that they may have functional interactions in the stress hormone network. Clarifying the roles of key ClBBXs in transcriptional regulation and mediating protein interactions will be an important task. Our comprehensive characterization of the watermelon ClBBX family provides vital clues for the in-depth analysis of their biological functions in stress and hormone signaling pathways.

Characterization of HSP70 family in watermelon (Citrullus lanatus): identification, structure, evolution, and potential function in response to ABA, cold and drought stress.

Watermelon (Citrullus lanatus) as a crop with important economic value, is widely cultivated around the world. The heat shock protein 70 (HSP70) family in plant is indispensable under stress conditions. However, no comprehensive analysis of watermelon HSP70 family is reported to date. In this study, 12 ClHSP70 genes were identified from watermelon, which were unevenly located in 7 out of 11 chromosomes and divided into three subfamilies. ClHSP70 proteins were predicted to be localized primarily in cytoplasm, chloroplast, and endoplasmic reticulum. Two pairs of segmental repeats and 1 pair of tandem repeats existed in ClHSP70 genes, and ClHSP70s underwent strong purification selection. There were many abscisic acid (ABA) and abiotic stress response elements in ClHSP70 promoters. Additionally, the transcriptional levels of ClHSP70s in roots, stems, true leaves, and cotyledons were also analyzed. Some of ClHSP70 genes were also strongly induced by ABA. Furthermore, ClHSP70s also had different degrees of response to drought and cold stress. The above data indicate that ClHSP70s may be participated in growth and development, signal transduction and abiotic stress response, laying a foundation for further analysis of the function of ClHSP70s in biological processes.

Ultrasonic-assisted extraction of flavonoids from Nitraria sibirica leaf using response surface methodology and their anti-proliferative activity on 3T3-L1 preadipocytes and antioxidant activities.

As both an edible and medicinal plant, Nitraria sibirica has been used as a natural remedy for indigestion and hypertension since ancient times in Central Asia. The ethanolic extract of N. sibirica leaves lowers blood pressure and blood lipids. We assume that these bioactivities are most likely related to the composition of flavonoids due to their dominant content. Therefore, we investigated bioactivity-oriented extraction parameters of flavonoids from N. sibirica. In this study, the ultrasonic-assisted extraction variables were optimized using a response surface methodology for optimal recoveries of total flavonoid content (TFC), anti-proliferative activity on 3T3-L1 preadipocytes and antioxidant capacities (DPPH) of N. sibirica leaf extract (NLE). The optimal extraction conditions of NLEs were as follows: ethanol concentration of 71.33%, feed-to-solvent ratio of 30.36 mL/g, extraction temperature of 69.48°C, extraction time of 25.27 min, extraction number of two times, the TFCs were 1.73 ± 0.01 mg RE/g d.w. (n = 4), IC50 value of preadipocytes was 259.42 ± 3.62 µg/mL (n = 4), and antioxidant capacity of 86.55 ± 3.71% (n = 4). After the purification of NLEs, the TFCs were 7.52 mg RE/g d.w., the inhibition capacity of IC50 was 143.50 µg/mL, and DPPH scavenging rate was 86.99%, which were approximately 4.34, 1.81, and 1.01 folds higher than before the purification of NLEs, respectively. Bioactive-oriented extraction of NLEs possessed the potential lipid lowering and antioxidant activities, which hold high research value for the development of natural medicines or new functional foods to treat or prevent metabolic diseases such as obesity.

Bcl6 drives stem-like memory macrophages differentiation to foster tumor progression.

Cancer development is a long-lasting process during which macrophages play a pivotal role. However, how macrophages maintain their cellular identity, persistence, expanding and pro-tumor property during malignant progression remains elusive. Inspired by the recent report of the activation of stem cell-like self-renewal mechanism in mature macrophages, we postulate that intra-tumoral macrophages might be trained to assume stem-like properties and memory-like activity favoring cancer development. Herein we demonstrated that tumor infiltrating macrophages rapidly converted into the CD11b+F4/80+Ly6C-Bcl6+ phenotype, and adopted stem cell-like properties involving expression of stemness-related genes, long-term persistence and self-renewing. Importantly, Bcl6+ macrophages stably maintained cell identity, gene signature, metabolic profile, and pro-tumor property even after long-term culture in tumor-free medium, which were hence termed stem cell-like memory macrophages (SMMs). Mechanistically, we showed that transcriptional factor Bcl6 co-opted the demethylase Tet2 and the deacetylase SIRT1 to confer the epigenetic imprinting and mitochondrial metabolic traits to SMMs, bolstering the stability and longevity of trained immunity in tumor-associated macrophages (TAMs). Furthermore, tumor-derived redHMGB1 was identified as the priming signal, which, through TLR4 and mTOR/AKT pathway, induced Bcl6-driven program underpinning SMMs generation. Collectively, our study uncovers a distinct macrophage population with a hybrid of stem cell and memory cell properties, and unveils a regulatory mechanism that integrates transcriptional, epigenetic and metabolic pathways to promote long-lasting pro-tumor immunity.

Corrigendum: Bcl6 Sets a Threshold for Antiviral Signaling by Restraining IRF7 Transcriptional Program.

This corrects the article DOI: 10.1038/srep18778.

Bcl6 Sets a Threshold for Antiviral Signaling by Restraining IRF7 Transcriptional Program.

The coordination of restraining and priming of antiviral signaling constitute a fundamental aspect of immunological functions. However, we currently know little about the molecular events that can translate the pathogenic cues into the appropriate code for antiviral defense. Our present study reports a specific role of B cell lymphoma (Bcl)6 as a checkpoint in the initiation of the host response to cytosolic RNA viruses. Remarkably, Bcl6 specifically binds to the interferon-regulatory factor (IRF)7 loci and restrains its transcription, thereby functioning as a negative regulator for interferon (IFN)-ß production and antiviral responses. The signal-controlled turnover of the Bcl6, most likely mediated by microRNA-127, coordinates the antiviral response and inflammatory sequelae. Accordingly, de-repression of Bcl6 resulted in a phenotypic conversion of macrophages into highly potent IFN-producing cells and rendered mice more resistant to pathogenic RNA virus infection. The failure to remove the Bcl6 regulator, however, impedes the antiviral signaling and exaggerates viral pneumonia in mice. We thus reveal a novel key molecular checkpoint to orchestrate antiviral innate immunity.

MiR-221 activates the NF-κB pathway by targeting A20.

MicroRNAs play an important role in regulating the inflammatory response, and are critically involved in the development of inflammatory disorders, including those affecting the lungs. While the microRNA miR-221 is involved in embryonic lung branching morphogenesis and epithelial cell development, its importance in lung inflammation has not been previously explored. In our current study, expression of miR-221 was selectively decreased by exposure to lipopolysaccharides (LPS) both in vitro and in vivo. Enforced expression of miR-221 significantly increased the production of proinflammatory cytokines TNF-α and IL-6, and enhanced the activation of NF-κB and MAPKs upon LPS stimulation. Accordingly, intratracheal stimulation of miR-221 was shown to aggravate endotoxin-induced acute lung injuries and inflammation in mice. Mechanistic studies showed that miR-221 directly targets A20, a master regulator of NF-κB and MAPK signaling, and thus represses inflammatory signaling. Restoration of A20 in macrophages abolished the stimulatory effect of miR-221 on production of proinflammatory cytokines. Together, these results indicate the presence of a novel miRNA-mediated feed-back mechanism that controls inflammation, and suggest involvement of aberrant miR-221 expression in the development of inflammatory lung disorders.