The entertainment videos pushed by WeChat promote the mental health of undergraduate students.

The present study addressed whether watching entertainment videos in succession could have a positive effect on the mental health of undergraduate students. Two experiments were designed. One hundred and sixteen university students participated in experiment 1. It aimed to explore whether watching motivational videos pushed by WeChat in continuous four weeks could affect mental health at the individual level, including mental health level and achievement goal orientation level. Experiment 2 enrolled 108 undergraduate students. It aimed to explore whether watching motivational and comedy videos pushed by WeChat in continuous four weeks could affect the mental health of undergraduate students at the social adaptation level, including interpersonal relationships and class atmosphere level. Results showed that entertainment videos pushed by WeChat in succession have significant positive effects on the university students' mental health and positive psychological quality.

A banana transcriptional repressor MaAP2a participates in fruit starch degradation during postharvest ripening.

Fruit postharvest ripening is a crucial course for many fruits with significant conversion of biosubstance, which forms an intricate regulatory network. Ethylene facilitates the ripening process in banana with a remarkable change of fruit starch, but the mechanism adjusting the expression of starch degradation-related enzyme genes is incompletely discovered. Here, we describe a banana APETALA2 transcription factor (MaAP2a) identified as a transcriptional repressor with its powerful transcriptional inhibitory activity. The transcriptional level of MaAP2a gradually decreased with the transition of banana fruit ripening, suggesting a passive role of MaAP2a in banana fruit ripening. Moreover, MaAP2a is a classic nucleoprotein and encompasses transcriptional repressor domain (EAR, LxLxLx). More specifically, protein-DNA interaction assays found that MaAP2a repressed the expression of 15 starch degradation-related genes comprising MaGWD1, MaPWD1, MaSEX4, MaLSF1, MaBAM1-MaBAM3, MaAMY2B/2C/3A/3C, MaMEX1/2, and MapGlcT2-1/2-2 via binding to the GCC-box or AT-rich motif of their promoters. Overall, these results reveal an original MaAP2a-mediated negative regulatory network involved in banana postharvest starch breakdown, which advances our cognition on banana fruit ripening and offers additional reference values for banana varietal improvement.

Regulation of Nir gene in Lactobacillus plantarum WU14 mediated by GlnR.

Nitrogen (N) is an essential element in the biosynthesis of key cellular components, such as proteins and nucleic acids, in all living organisms. Nitrite, as a form of nitrogen utilization, is the main nutrient for microbial growth. However, nitrite is a potential carcinogen that combines with secondary amines, which are breakdown products of proteins, to produce N-nitroso compounds that are strongly carcinogenic. Nitrite reductase (Nir) produced by microorganisms can reduce nitrite. Binding of GlnR to the promoter of nitrogen metabolism gene can regulate the expression of Nir operon. In this study, nitrite-resistant Lactobacillus plantarum WU14 was isolated from Pickles and its protease Nir was analyzed. GlnR-mediated regulation of L. plantarum WU14 Nir gene was investigated in this study. New GlnR and Nir genes were obtained from L. plantarum WU14. The regulation effect of GlnR on Nir gene was examined by gel block test, yeast two-hybrid system, bacterial single hybrid system and qRT-RCR. Detailed analysis showed that GlnR ound to the Nir promoter region and interacted with Nir at low nitrite concentrations, positively regulating the expression of NIR. However, the transcription levels of GlnR and Nir decreased gradually with increasing nitrite concentration. The results of this study improve our understanding of the function of the Nir operon regulatory system and serve as the ground for further study of the signal transduction pathway in lactic acid bacteria.

Biodegradation and Detoxification of Azo Dyes by Halophilic/Halotolerant Microflora Isolated From the Salt Fields of Tibet Autonomous Region China.

This study aimed to decolorize azo dyes in high-salt industrial wastewater under high-salt and low oxygen conditions using extreme halophilic/halotolerant bacteria screened from the salt fields of Tibet, which consisted of Enterococcus, unclassified Enterobacteriaceae, Staphylococcus, Bacillus, and Kosakonia. Under the optimal conditions, 600 mg/l Congo red, Direct Black G (DBG), Amaranth, methyl red, and methyl orange could be completely decolorized in 24, 8, 8, 12, and 12 h, respectively. When the DBG concentration was 600 mg/l, NADH-DCIP, laccase, and azo reductase were confirmed to be the primary reductase and oxidase during the degradation process, and the degradation pathways were verified. The microflora could not only tolerate changes in salt concentrations of 0-80 g/l, but also displayed strong degradative ability. Under high-salt concentrations (≥ 60 g/l NaCl), NADH-DCIP reductase was primarily used to decolorize the azo dye. However, under low salt concentrations (≤ 40 g/l NaCl), azo reductase began to function, and manganese peroxidase and lignin peroxidase could cooperate to participate in DBG degradation. Additionally, the halophilic/halophilic microflora was shown to convert the toxic DBG dye to metabolites of low toxicity based on phytotoxicity analysis, and a new mechanism for the microflora to degrade DBG was proposed based on intermediates identified by liquid chromatography-mass spectrometry (LC-MS). This study revealed that the halophilic/halophilic microflora has effective ecological and industrial value for treating wastewater from the textile industry.

Optimization of fermentation conditions for production of l-arabinose isomerase of Lactobacillus plantarum WU14.

As a substitute sweetener for sucrose, d-tagatose is widely used in products, such as health drinks, yogurt, fruit juices, baked goods, confectionery, and pharmaceutical preparations. In the fermentation process of l-AI produced by Lactobacillus plantarum, d-tagatose is produced through biotransformation and this study was based on the fermentation process of Lactobacillus plantarum WU14 producing l-AI to further research the biotransformation and separation process of d-tagatose. The kinetics of cell growth, substrate consumption, and l-arabinose isomerase formation were established by nonlinear fitting, and the fitting degrees were 0.996, 0.994, and 0.991, respectively, which could better reflect the change rule of d-tagatose biotransformation in the fermentation process of L. plantarum WU14. The separation process of d-tagatose was identified by decolorization, protein removal, desalination, and freeze drying, initially. Finally, the volume ratio of whole cell catalysts, d-galactose, and borate was 5:1:2 at 60°C, pH 7.17 through borate complexation; then, after 24 hr of conversion, the yield of d-tagatose was 58 g/L.

A Novel Glucose Isomerase from Caldicellulosiruptor bescii with Great Potentials in the Production of High-Fructose Corn Syrup.

Glucose isomerase (GI) that catalyzes the conversion of D-glucose to D-fructose is one of the most important industrial enzymes for the production of high-fructose corn syrup (HFCS). In this study, a novel GI (CbGI) was cloned from Caldicellulosiruptor bescii and expressed in Escherichia coli. The purified recombinant CbGI (rCbGI) showed neutral and thermophilic properties. It had optimal activities at pH 7.0 and 80°C and retained stability at 85°C. In comparison with other reported GIs, rCbGI exhibited higher substrate affinity (Km = 42.61 mM) and greater conversion efficiency (up to 57.3% with 3M D-glucose as the substrate). The high catalytic efficiency and affinity of this CbGI is much valuable for the cost-effective production of HFCS.

MaMYB4 Recruits Histone Deacetylase MaHDA2 and Modulates the Expression of ω-3 Fatty Acid Desaturase Genes during Cold Stress Response in Banana Fruit.

Linoleic acid (LA; C18:2) and α-linolenic acid (ALA; C18:3) are two essential unsaturated fatty acids that play indispensable roles in maintaining membrane integrity in cold stress, and ω-3 fatty acid desaturases (FADs) are responsible for the transformation of LA into ALA. However, how this process is regulated at transcriptional and posttranscriptional levels remains largely unknown. In this study, an MYB transcription factor, MaMYB4, of a banana fruit was identified and found to target several ω-3 MaFADs, including MaFAD3-1, MaFAD3-3, MaFAD3-4 and MaFAD3-7, and repress their transcription. Intriguingly, the acetylation levels of histones H3 and H4 in the promoters of ω-3 MaFADs were elevated in response to cold stress, which was correlated with the enhancement in the transcription levels of ω-3 MaFADs and the ratio of ALA/LA. Moreover, a histone deacetylase MaHDA2 physically interacted with MaMYB4, thereby leading to the enhanced MaMYB4-mediated transcriptional repression of ω-3 MaFADs. Collectively, these data demonstrate that MaMYB4 might recruit MaHDA2 to repress the transcription of ω-3 MaFADs by affecting their acetylation levels, thus modulating fatty acid biosynthesis. Our findings provided new molecular insights into the regulatory mechanisms of fatty acid biosynthesis in cold stress in fruits.

A banana R2R3-MYB transcription factor MaMYB3 is involved in fruit ripening through modulation of starch degradation by repressing starch degradation-related genes and MabHLH6.

Starch degradation is a necessary process determining banana fruit quality during ripening. Many starch degradation-related genes are well studied. However, the transcriptional regulation of starch degradation during banana fruit ripening remains poorly understood. In this study, we identified a MYB transcription factor (TF) termed MaMYB3, as a putative protein binding the promoter of MaGWD1, a member of glucan water dikinase (GWD) family which has been demonstrated as an important enzyme of starch degradation. MaMYB3 was ripening- and ethylene-repressible, and its expression was negatively correlated with starch degradation. Acting as a nucleus-localized transcriptional repressor, MaMYB3 repressed the transcription of 10 starch degradation-related genes, including MaGWD1, MaSEX4, MaBAM7-MaBAM8, MaAMY2B, MaAMY3, MaAMY3A, MaAMY3C, MaMEX1, and MapGlcT2-1, by directly binding to their promoters. Interestingly, a previously identified activator of starch degradation-related genes, MabHLH6, was also suppressed by MaMYB3. The ectopic overexpression of MaMYB3 in tomato down-regulated the expression of starch degradation-related genes, inhibited starch degradation and delayed fruit ripening. Based on these findings, we conclude that MaMYB3 negatively impacts starch degradation by directly repressing starch degradation-related genes and MabHLH6, and thereby delays banana fruit ripening. Collectively, our study expands our understanding of the complex transcriptional regulatory hierarchy modulating starch degradation during fruit ripening.

A comprehensive investigation of starch degradation process and identification of a transcriptional activator MabHLH6 during banana fruit ripening.

Although starch degradation has been well studied in model systems such as Arabidopsis leaves and cereal seeds, this process in starchy fruits during ripening, especially in bananas, is largely unknown. In this study, 38 genes encoding starch degradation-related proteins were identified and characterized from banana fruit. Expression analysis revealed that 27 candidate genes were significantly induced during banana fruit ripening, with concomitant conversion of starch-to-sugars. Furthermore, iTRAQ-based proteomics experiments identified 18 starch degradation-associated enzymes bound to the surface of starch granules, of which 10 were markedly up-regulated during ripening. More importantly, a novel bHLH transcription factor, MabHLH6, was identified based on a yeast one-hybrid screening using MaGWD1 promoter as a bait. Transcript and protein levels of MabHLH6 were also increased during fruit ripening. Electrophoretic mobility shift assays, chromatin immunoprecipitation and transient expression experiments confirmed that MabHLH6 activates the promoters of 11 starch degradation-related genes, including MaGWD1, MaLSF2, MaBAM1, MaBAM2, MaBAM8, MaBAM10, MaAMY3, MaAMY3C, MaISA2, MaISA3 and MapGlcT2-2 by recognizing their E-box (CANNTG) motifs present in the promoters. Collectively, these findings suggest that starch degradation during banana fruit ripening may be attributed to the complex actions of numerous enzymes related to starch breakdown at transcriptional and translational levels, and that MabHLH6 may act as a positive regulator of this process via direct activation of a series of starch degradation-related genes.

The transcriptional regulatory network mediated by banana (Musa acuminata) dehydration-responsive element binding (MaDREB) transcription factors in fruit ripening.

Fruit ripening is a complex, genetically programmed process involving the action of critical transcription factors (TFs). Despite the established significance of dehydration-responsive element binding (DREB) TFs in plant abiotic stress responses, the involvement of DREBs in fruit ripening is yet to be determined. Here, we identified four genes encoding ripening-regulated DREB TFs in banana (Musa acuminata), MaDREB1, MaDREB2, MaDREB3, and MaDREB4, and demonstrated that they play regulatory roles in fruit ripening. We showed that MaDREB1-MaDREB4 are nucleus-localized, induced by ethylene and encompass transcriptional activation activities. We performed a genome-wide chromatin immunoprecipitation and high-throughput sequencing (ChIP-Seq) experiment for MaDREB2 and identified 697 genomic regions as potential targets of MaDREB2. MaDREB2 binds to hundreds of loci with diverse functions and its binding sites are distributed in the promoter regions proximal to the transcriptional start site (TSS). Most of the MaDREB2-binding targets contain the conserved (A/G)CC(G/C)AC motif and MaDREB2 appears to directly regulate the expression of a number of genes involved in fruit ripening. In combination with transcriptome profiling (RNA sequencing) data, our results indicate that MaDREB2 may serve as both transcriptional activator and repressor during banana fruit ripening. In conclusion, our study suggests a hierarchical regulatory model of fruit ripening in banana and that the MaDREB TFs may act as transcriptional regulators in the regulatory network.

The Banana Transcriptional Repressor MaDEAR1 Negatively Regulates Cell Wall-Modifying Genes Involved in Fruit Ripening.

Ethylene plays an essential role in many biological processes including fruit ripening via modulation of ethylene signaling pathway. Ethylene Response Factors (ERFs) are key transcription factors (TFs) involved in ethylene perception and are divided into AP2, RAV, ERF, and DREB sub-families. Although a number of studies have implicated the involvement of DREB sub-family genes in stress responses, little is known about their roles in fruit ripening. In this study, we identified a DREB TF with a EAR motif, designated as MaDEAR1, which is a nucleus-localized transcriptional repressor. Expression analysis indicated that MaDEAR1 expression was repressed by ethylene, with reduced levels of histone H3 and H4 acetylation at its regulatory regions during fruit ripening. In addition, MaDEAR1 promoter activity was also suppressed in response to ethylene treatment. More importantly, MaDEAR1 directly binds to the DRE/CRT motifs in promoters of several cell wall-modifying genes including MaEXP1/3, MaPG1, MaXTH10, MaPL3, and MaPME3 associated with fruit softening during ripening and represses their activities. These data suggest that MaDEAR1 acts as a transcriptional repressor of cell wall-modifying genes, and may be negatively involved in ethylene-mediated ripening of banana fruit. Our findings provide new insights into the involvement of DREB TFs in the regulation of fruit ripening.

Banana Transcription Factor MaERF11 Recruits Histone Deacetylase MaHDA1 and Represses the Expression of MaACO1 and Expansins during Fruit Ripening.

Phytohormone ethylene controls diverse developmental and physiological processes such as fruit ripening via modulation of ethylene signaling pathway. Our previous study identified that ETHYLENE RESPONSE FACTOR11 (MaERF11), a transcription factor in the ethylene signaling pathway, negatively regulates the ripening of banana, but the mechanism for the MaERF11-mediated transcriptional regulation remains largely unknown. Here we showed that MaERF11 has intrinsic transcriptional repression activity in planta. Electrophoretic mobility shift assay and chromatin immunoprecipitation analyses demonstrated that MaERF11 binds to promoters of three ripening-related Expansin genes, MaEXP2, MaEXP7 and MaEXP8, as well as an ethylene biosynthetic gene MaACO1, via the GCC-box motif. Furthermore, expression patterns of MaACO1, MaEXP2, MaEXP7, and MaEXP8 genes are correlated with the changes of histone H3 and H4 acetylation level during fruit ripening. Moreover, we found that MaERF11 physically interacts with a histone deacetylase, MaHDA1, which has histone deacetylase activity, and the interaction significantly strengthens the MaERF11-mediated transcriptional repression of MaACO1 and Expansins Taken together, these findings suggest that MaERF11 may recruit MaHDA1 to its target genes and repress their expression via histone deacetylation.

Banana fruit VQ motif-containing protein5 represses cold-responsive transcription factor MaWRKY26 involved in the regulation of JA biosynthetic genes.

Most harvested fruits and vegetables are stored at low temperature but many of them are highly sensitive to chilling injury. Jasmonic acid (JA), a plant hormone associated with various stress responses, is known to reduce chilling injury in fruits. However, little is known about the transcriptional regulation of JA biosynthesis in relation to cold response of fruits. Here, we show the involvement of a Group I WRKY transcription factor (TF) from banana fruit, MaWRKY26, in regulating JA biosynthesis. MaWRKY26 was found to be nuclear-localized with transcriptional activation property. MaWRKY26 was induced by cold stress or by methyl jasmonate (MeJA), which enhances cold tolerance in banana fruit. More importantly, MaWRKY26 transactivated JA biosynthetic genes MaLOX2, MaAOS3 and MaOPR3 via binding to their promoters. Further, MaWRKY26 physically interacted with a VQ motif-containing protein MaVQ5, and the interaction attenuated MaWRKY26-induced transactivation of JA biosynthetic genes. These results strongly suggest that MaVQ5 might act as a repressor of MaWRKY26 in activating JA biosynthesis. Taken together, our findings provide new insights into the transcriptional regulation of JA biosynthesis in response to cold stress and a better understanding of the molecular aspects of chilling injury in banana fruit.

The banana fruit Dof transcription factor MaDof23 acts as a repressor and interacts with MaERF9 in regulating ripening-related genes.

The DNA binding with one finger (Dof) proteins, a family of plant-specific transcription factors, are involved in a variety of plant biological processes. However, little information is available on their involvement in fruit ripening. We have characterized 25 MaDof genes from banana fruit (Musa acuminata), designated as MaDof1-MaDof25 Gene expression analysis in fruit subjected to different ripening conditions revealed that MaDofs were differentially expressed during different stages of ripening. MaDof10, 23, 24, and 25 were ethylene-inducible and nuclear-localized, and their transcript levels increased during fruit ripening. Moreover, yeast two-hybrid and bimolecular fluorescence complementation analyses demonstrated a physical interaction between MaDof23 and MaERF9, a potential regulator of fruit ripening reported in a previous study. We determined that MaDof23 is a transcriptional repressor, whereas MaERF9 is a transcriptional activator. We suggest that they might act antagonistically in regulating 10 ripening-related genes, including MaEXP1/2/3/5, MaXET7, MaPG1, MaPME3, MaPL2, MaCAT, and MaPDC, which are associated with cell wall degradation and aroma formation. Taken together, our findings provide new insight into the transcriptional regulation network controlling banana fruit ripening.

A ripening-induced transcription factor MaBSD1 interacts with promoters of MaEXP1/2 from banana fruit.

KEY MESSAGE: The ripening-induced MaBSD1 acts as a transcriptional activator, and might be involved in banana fruit ripening partly through directly activating the expression of two ripening-associated genes, MaEXP1/2. BSD (BTF2-like transcription factors, synapse-associated proteins and DOS2-like proteins) transcription factors are characterized by a typical BSD domain. However, little information is available concerning their possible roles in plant growth and development, especially in fruit ripening. In the present study, one BSD gene, designated as MaBSD1, was isolated from banana fruit. MaBSD1 has an open reading frame (ORF) of 921 bp which encodes a polypeptide of 306 amino acid residues with molecular weight of 34.80 kDa, and isoelectric point (pI) of 4.54. Subcellular localization and transcriptional activation assays showed that MaBSD1 was localized in both the nucleus and cytoplasm and possessed transcriptional activity. RT-qPCR and promoter activity analysis indicated that MaBSD1 was ethylene and ripening inducible, and the accumulation of MaBSD1 transcript was correlated well with the evolution of ethylene production and ripening process. Moreover, transient assay showed that MaBSD1 could activate the expression of two cell wall modification-related genes, MaEXP1/2, via directly interacting with their promoters. Together, these data suggest that ripening-induced MaBSD1 acts as a transcriptional activator and might be associated with banana fruit ripening, at least partially through directly activating the expression of MaEXP1/2, expanding the limited information concerning the BSD transcription factor in relation to fruit ripening.

Banana ethylene response factors are involved in fruit ripening through their interactions with ethylene biosynthesis genes.

The involvement of ethylene response factor (ERF) transcription factor (TF) in the transcriptional regulation of ethylene biosynthesis genes during fruit ripening remains largely unclear. In this study, 15 ERF genes, designated as MaERF1-MaERF15, were isolated and characterized from banana fruit. These MaERFs were classified into seven of the 12 known ERF families. Subcellular localization showed that MaERF proteins of five different subfamilies preferentially localized to the nucleus. The 15 MaERF genes displayed differential expression patterns and levels in peel and pulp of banana fruit, in association with four different ripening treatments caused by natural, ethylene-induced, 1-methylcyclopropene (1-MCP)-delayed, and combined 1-MCP and ethylene treatments. MaERF9 was upregulated while MaERF11 was downregulated in peel and pulp of banana fruit during ripening or after treatment with ethylene. Furthermore, yeast-one hybrid (Y1H) and transient expression assays showed that the potential repressor MaERF11 bound to MaACS1 and MaACO1 promoters to suppress their activities and that MaERF9 activated MaACO1 promoter activity. Interestingly, protein-protein interaction analysis revealed that MaERF9 and -11 physically interacted with MaACO1. Taken together, these results suggest that MaERFs are involved in banana fruit ripening via transcriptional regulation of or interaction with ethylene biosynthesis genes.

Molecular characterization of banana NAC transcription factors and their interactions with ethylene signalling component EIL during fruit ripening.

The plant-specific NAC (NAM, ATAF1/2, and CUC2) transcription factors (TFs) play important roles in plant growth, development, and stress responses. However, the precise role of NAC TFs in relation to fruit ripening is poorly understood. In this study, six NAC genes, designated MaNAC1-MaNAC6, were isolated and characterized from banana fruit. Subcellular localization showed that MaNAC1-MaNAC5 proteins localized preferentially to the nucleus, while MaNAC6 was distributed throughout the entire cell. A transactivation assay in yeast demonstrated that MaNAC4 and MaNAC6, as well as their C-terminal regions, possessed trans-activation activity. Gene expression profiles in fruit with four different ripening characteristics, including natural, ethylene-induced, 1-methylcyclopropene (1-MCP)-delayed, and a combination of 1-MCP with ethylene treatment, revealed that the MaNAC genes were differentially expressed in peel and pulp during post-harvest ripening. MaNAC1 and MaNAC2 were apparently upregulated by ethylene in peel and pulp, consistent with the increase in ethylene production. In contrast, MaNAC3 in peel and pulp and MaNAC5 in peel were constitutively expressed, and transcripts of MaNAC4 in peel and pulp and MaNAC6 in peel decreased, while MaNAC5 or MaNAC6 in pulp increased slightly during fruit ripening. Furthermore, the MaNAC2 promoter was activated after ethylene application, further enhancing the involvement of MaNAC2 in fruit ripening. More importantly, yeast two-hybrid and bimolecular fluorescence complementation analyses confirmed that MaNAC1/2 physically interacted with a downstream component of ethylene signalling, ethylene insensitive 3 (EIN3)-like protein, termed MaEIL5, which was downregulated during ripening. Taken together, these results suggest that MaNACs such as MaNAC1/MaNAC2, may be involved in banana fruit ripening via interaction with ethylene signalling components.