CTLA-4 blockade induces tumor pyroptosis via CD8+ T cells in head and neck squamous cell carcinoma.

Immune checkpoint blockade (ICB) treatment has demonstrated excellent medical effects in oncology, and it is one of the most sought after immunotherapies for tumors. However, there are several issues with ICB therapy, including low response rates and a lack of effective efficacy predictors. Gasdermin-mediated pyroptosis is a typical inflammatory death mode. We discovered that increased expression of gasdermin protein was linked to a favorable tumor immune microenvironment and prognosis in head and neck squamous cell carcinoma (HNSCC). We used the mouse HNSCC cell lines 4MOSC1 (responsive to CTLA-4 blockade) and 4MOSC2 (resistant to CTLA-4 blockade) orthotopic models and demonstrated that CTLA-4 blockade treatment induced gasdermin-mediated pyroptosis of tumor cells, and gasdermin expression positively correlated to the effectiveness of CTLA-4 blockade treatment. We found that CTLA-4 blockade activated CD8+ T cells and increased the levels of interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α) cytokines in the tumor microenvironment. These cytokines synergistically activated the STAT1/IRF1 axis to trigger tumor cell pyroptosis and the release of large amounts of inflammatory substances and chemokines. Collectively, our findings revealed that CTLA-4 blockade triggered tumor cells pyroptosis via the release of IFN-γ and TNF-α from activated CD8+ T cells, providing a new perspective of ICB.

MicroRNA-127-3p Inhibits Cardiomyocyte Inflammation and Apoptosis after Acute Myocardial Infarction via Targeting CDKN3.

Given the potential role of microRNA (miRNA) in the pathological process of ischemic heart disease, clinical patients with acute myocardial infarction (AMI) were recruited and serum miR-127-3p levels in the patients were tested. In vitro, the effects of miR-127-3p on cardiomyocyte apoptosis and inflammation induced by hypoxia and reoxygenation (H/R) were also elucidated in AC16 cells.Collection of serum samples from 113 AMI patients and 104 healthy controls was done. Human cardiomyocyte cell line AC16 was exposed to the H/R condition for the cell function experiments. qRT-PCR was applied for mRNA detection, and cell viability and apoptosis were evaluated. To assess inflammatory response, an enzyme-linked immunosorbent assay was carried out. For the target gene analysis, luciferase reporter assay was accomplished.MiR-127-3p was significantly reduced in the serum of AMI patients, which was negatively correlated with CDKN3 mRNA levels. Serum miR-127-3p was negatively correlated with Scr, cTnI, CK-MB, IL-6, and TNF-α. CDKN3 serves as a target gene of miR-127-3p, its mRNA levels were reduced by miR-127-3p overexpression. H/R treatment caused the suppression of cell viability and the promotion of cell apoptosis, which was changeover by miR-127-3p overexpression. Furthermore, MiR-127-3p overexpression inhibited cell inflammatory response. The rescue experiments revealed that CDKN3 overexpression canceled the protective influence of miR-127-3p against cardiomyocyte injury and inflammatory response.MiR-127-3p can alleviate AMI-induced cardiomyocyte apoptosis and cardiac dysfunction, which is related to its anti-inflammatory effect and its downstream CDKN3 gene.

Overexpression of CD168 is related to poor prognosis in oral squamous cell carcinoma.

OBJECTIVES: Receptor for hyaluronic acid (HA)-mediated motility (RHAMM) is also known as CD168. This study proposed to elucidate the prognostic and clinicopathological significance of CD168 expression in oral squamous cell carcinoma (OSCC). MATERIALS AND METHODS: Immune staining of a human tissue microarray and Western blot were used to reveal the expression level of CD168 in OSCC. Correlations between clinicopathological indexes and CD168 expression in OSCC patients were assessed. RESULTS: Increased expression of CD168 was detected in OSCC tissues. High expression of CD168 indicated worse survival of patients (p < .05). Furthermore, high expression of CD168 was related to pathological grade in OSCC (p < .05). CD168 expression was positively related to programmed death ligand 1 (PD-L1), CKLF-like MARVEL transmembrane domain-containing protein 6 (CMTM6), B7 homology 4 protein (B7-H4), CD44, CD133, and Slug expression in OSCC. CONCLUSION: This study revealed the overexpression of CD168 in OSCC and shed light on the prognostic significance of CD168 expression in OSCC patients.

A maize NAC transcription factor, ZmNAC34, negatively regulates starch synthesis in rice.

KEY MESSAGE: ZmNAC34 might function as an important regulator of starch synthesis by decreasing total starch accumulation and soluble sugar content and increasing amylose fractions. Starch is a major component in endosperm and directly influences seed yield and the cooking quality of cereal grains. Starch is synthesized through a series of complex biological processes. Nevertheless, the mechanism by which starch biosynthesis is regulated in maize is still unclear. In this study, ZmNAC34, a NAC transcription factor related to starch synthesis, was screened based on transcriptome sequencing data. Subsequent qRT-PCR analysis showed that ZmNAC34 is specifically expressed in maize endosperm. Transactivation and subcellular localization assays revealed that ZmNAC34 possesses two characteristics of transcription factors: nuclear localization and transactivation activity. Overexpression of ZmNAC34 in rice decreased total starch accumulation and soluble sugar content, while increased amylose fractions. Meanwhile, the transgenic seeds exhibited alterant starch structure and abnormal morphology. In addition, compared with WT seeds, most of the 17 starch biosynthesis-related genes were significantly upregulated in transgenic seeds from 6 to 15 DAP (day after pollination). These data reveal that ZmNAC34 might function as an important regulator of starch synthesis, thus providing a new perspective on controlling seed yield and quality.

Transcriptome analysis reveals comprehensive responses to cadmium stress in maize inoculated with arbuscular mycorrhizal fungi.

Biological strategy of utilization of plants-microbe's interactions to remediate cadmium (Cd) contaminated soils is effective and practical. However, limited evidence at transcriptome level is available about how microbes work with host plants to alleviate Cd stress. In the present study, comparative transcriptomic analysis was performed between maize seedlings inoculated with arbuscular mycorrhizal (AM) fungi and non-AM fungi inoculation under distinct concentrations of CdCl2 (0, 25, and 50 mg per kg soil). Significantly higher levels of Cd were found in root tissues of maize colonized by AM fungi, whereas, Cd content was reduced as much as 50% in leaf tissues when compared to non-AM seedlings, indicating that symbiosis between AM fungi and maize seedlings can significantly block translocation of Cd from roots to leaf tissues. Moreover, a total of 5827 differentially expressed genes (DEG) were determined and approximately 68.54% DEGs were downregulated when roots were exposed to high Cd stress. In contrast, 67.16% (595) DEGs were significantly up-regulated when seedlings were colonized by AM fungi under 0 mg CdCl2. Based on hierarchical clustering analysis, global expression profiles were split into eight distinct clusters. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that hundreds of genes functioning in plant hormone signal transduction, mitogen-activated protein kinase (MAPK) signaling pathway and glutathione metabolism were enriched. Furthermore, MapMan pathway analysis indicated a more comprehensive overview response, including hormone metabolism, especially in JA, glutathione metabolism, transcription factors and secondary metabolites, to Cd stress in mycorrhizal maize seedlings. These results provide an overview, at the transcriptome level, of how inoculation of maize seedlings by AM fungi could facilitate the relief of Cd stress.

DNA Repair Gene ZmRAD51A Improves Rice and Arabidopsis Resistance to Disease.

RAD51 (DNA repair gene) family genes play ubiquitous roles in immune response among species from plants to mammals. In this study, we cloned the ZmRAD51A gene (a member of RAD51) in maize and generated ZmRAD51A overexpression (ZmRAD51A-OE) in rice, tobacco, and Arabidopsis. The expression level of ZmRAD51A was remarkably induced by salicylic acid (SA) application in maize, and the transient overexpression of ZmRAD51A in tobacco induced a hypersensitive response. The disease resistance was significantly enhanced in ZmRAD51A- OE (overexpressing) plants, triggering an increased expression of defense-related genes. High-performance liquid chromatography (HPLC) analysis showed that, compared to control lines, ZmRAD51A-OE in rice plants resulted in higher SA levels, and conferred rice plants resistance to Magnaporthe oryzae. Moreover, the ZmRAD51A-OE Arabidopsis plants displayed increased resistance to Pseudomonas syringae pv. tomato DC3000 when compared to wild types. Together, our results provide the evidence that, for the first time, the maize DNA repair gene ZmRAD51A plays an important role in in disease resistance.

Identification of Long Non-Coding RNAs and the Regulatory Network Responsive to Arbuscular Mycorrhizal Fungi Colonization in Maize Roots.

Recently, long noncoding RNAs (lncRNAs) have emerged as vital regulators of many biological processes in animals and plants. However, to our knowledge no investigations on plant lncRNAs which respond to arbuscular mycorrhizal (AM) fungi have been reported thus far. In this study, maize roots colonized with AM fungus were analyzed by strand-specific RNA-Seq to identify AM fungi-responsive lncRNAs and construct an associated regulatory network. A total of 1837 differentially expressed protein coding genes (DEGs) were identified from maize roots with Rhizophagus irregularis inoculation. Many AM fungi-responsive genes were homologs to MtPt4, STR, STR2, MtFatM, and enriched pathways such as fatty acid biosynthesis, response to phosphate starvation, and nitrogen metabolism are consistent with previous studies. In total, 5941 lncRNAs were identified, of which more than 3000 were new. Of those, 63 lncRNAs were differentially expressed. The putative target genes of differentially expressed lncRNAs (DELs) were mainly related to phosphate ion transmembrane transport, cellular response to potassium ion starvation, and lipid catabolic processes. Regulatory network analysis showed that DELs might be involved in the regulation of bidirectional nutrient exchange between plant and AM fungi as mimicry of microRNA targets. The results of this study can broaden our knowledge on the interaction between plant and AM fungi.

Expression of a maize NBS gene ZmNBS42 enhances disease resistance in Arabidopsis.

KEY MESSAGE: Expression of the ZmNBS42 in Arabidopsis plants conferred resistance to bacterial pathogens, providing potential resistance enhancement of maize in further genetic breeding. Nucleotide-binding site (NBS) domain proteins play critical roles in disease resistance. In this study, we isolate a novel NBS gene ZmNBS42 from maize and systematically investigate its function on disease resistance. We find that the expression levels of ZmNBS42 in maize leaf were strikingly increased in response to Bipolaris maydis inoculation and SA treatment. The spatial expression pattern analysis reveals that, during development, ZmNBS42 is ubiquitously highly expressed in maize root, leaf, stem, internode and seed, but lowly expressed in pericarp and embryo. To better understand the roles of ZmNBS42, we overexpressed ZmNBS42 in heterologous systems. Transient overexpression of ZmNBS42 in the leaves of Nicotiana benthamiana induces a hypersensitive response. ZmNBS42 overexpression (ZmNBS42-OE) Arabidopsis plants produced more SA content than Col-0 plants, and increased the expression levels of some defense-responsive genes compared to Col-0 plants. Moreover, the ZmNBS42-OE Arabidopsis plants displayed enhanced resistance against Pseudomonas syringae pathovar tomato DC3000 (Pst DC3000). These results together suggest that ZmNBS42 can serve as an important regulator in disease resistance, thus better understanding of ZmNBS42 would benefit the resistance enhancement in maize breeding programs.

Identification of Arbuscular Mycorrhiza Fungi Responsive microRNAs and Their Regulatory Network in Maize.

Maize can form symbiotic relationships with arbuscular mycorrhiza (AM) fungus to increase productivity and resistance, but the miRNAs in maize responsible for this process have not been discovered. In this study, 155 known and 28 novel miRNAs were identified by performing high-throughput sequencing of sRNA in maize roots colonized by AM fungi. Similar to the profiles in other AM-capable plants, a large proportion of identified maize miRNAs were 24 nt in length. Fourteen and two miRNAs were significantly down- and up-regulated in response to AM fungus Glomus intraradices inoculation, respectively, suggesting potential roles of these miRNAs in AM symbiosis. Interestingly, 12 of 14 significantly down-regulated known maize miRNAs belong to the miR399 family, which was previously reported to be involved in the interaction between Medicago truncatula and AM fungi. This result indicated that the miR399 family should regulate AM symbiosis conservatively across different plant lineages. Pathway and network analyses showed that the differentially expressed miRNAs might regulate lipid metabolism and phosphate starvation response in maize during the symbiosis process via their target genes. Several members of the miR399 family and the miR397 family should be involved in controlling the fatty acid metabolism and promoting lipid delivering from plants to AM fungi. To the best of our knowledge, this is the first report on miRNAs mediating fatty acids from plant to AM fungi. This study provides insight into the regulatory roles of miRNAs in the symbiosis between plants and AM fungi.

Systematic Identification, Evolution and Expression Analysis of the Zea mays PHT1 Gene Family Reveals Several New Members Involved in Root Colonization by Arbuscular Mycorrhizal Fungi.

The Phosphate Transporter1 (PHT1) family of genes plays pivotal roles in the uptake of inorganic phosphate from soils. However, there is no comprehensive report on the PHT1 family in Zea mays based on the whole genome. In the present study, a total of 13 putative PHT1 genes (ZmPHT1;1 to 13) were identified in the inbred line B73 genome by bioinformatics methods. Then, their function was investigated by a yeast PHO84 mutant complementary experiment and qRT-PCR. Thirteen ZmPHT1 genes distributed on six chromosomes (1, 2, 5, 7, 8 and 10) were divided into two paralogues (Class A and Class B). ZmPHT1;1/ZmPHT1;9 and ZmPHT1;9/ZmPHT1;13 are produced from recent segmental duplication events. ZmPHT1;1/ZmPHT1;13 and ZmPHT1;8/ZmPHT1;10 are produced from early segmental duplication events. All 13 putative ZmPHT1s can completely or partly complement the yeast Pi-uptake mutant, and they were obviously induced in maize under low Pi conditions, except for ZmPHT1;1 (p < 0.01), indicating that the overwhelming majority of ZmPHT1 genes can respond to a low Pi condition. ZmPHT1;2, ZmPHT1;4, ZmPHT1;6, ZmPHT1;7, ZmPHT1;9 and ZmPHT1;11 were up-regulated by arbuscular mycorrhizal fungi (AMF), implying that these genes might participate in mediating Pi absorption and/or transport. Analysis of the promoters revealed that the MYCS and P1BS element are widely distributed on the region of different AMF-inducible ZmPHT1 promoters. In light of the above results, five of 13 ZmPHT1 genes were newly-identified AMF-inducible high-affinity phosphate transporters in the maize genome. Our results will lay a foundation for better understanding the PHT1 family evolution and the molecular mechanisms of inorganic phosphate transport under AMF inoculation.

Different evolutionary patterns among intronless genes in maize genome.

Intronless genes, as a characteristic feature of prokaryotes, are an important resource for the study of the evolution of gene architecture in eukaryotes. In the study, 14,623 (36.87%) intronless genes in maize were identified and the percentage is greater than that of other monocots and algae. The number of maize intronless genes on each chromosome has a significant linear correlation with the number of total genes on the chromosome and the length of the chromosomes. Intronless genes in maize play important roles in translation and energy metabolism. Evolutionary analysis revealed that 2601 intronless genes conserved among the three domains of life and 2323 intronless genes that had no homology with genes of other species. These two sets of intronless genes were distinct in genetic features, physical locations and function. These results provided a useful source to understand the evolutionary patterns of related genes and genomes and some intronless genes are good candidates for subsequent functional analyses specifically.

Genome-wide identification and characterization of maize expansin genes expressed in endosperm.

By promoting cell wall loosening, expansins contribute to cell enlargement during various developmental processes. Nevertheless, the role of expansins in the expansion and development of endosperm--a major seed component whose cell size is significantly associated with grain yield--is poorly understood. To explore associated biological processes and the evolution of expansins in maize, we performed a systematic analysis of the expansin gene family encompassing gene structure, phylogeny, chromosomal location, gene duplication, and gene ontology. A total of 88 maize expansin genes (ZmEXPs) were identified and categorized into three subfamilies according to their phylogenetic relationships. Expression patterns of ZmEXPs were also investigated in nine different tissues by semi-quantitative RT-PCR. The expression of eight ZmEXPs was detected in endosperm, with five showing endosperm-specific expression. Quantitative RT-PCR was used to analyze expression patterns of the eight ZmEXPs in endosperm (10 days after pollination) under abscisic acid (ABA) and gibberellic acid (GA3) treatments. All eight ZmEXPs were found to be significantly regulated by ABA and GA3 in endosperm, suggesting important roles for these hormones in the regulation of ZmEXPs during endosperm development. Our results provide essential information for ZmEXPs cloning and functional exploration, which will assist research on expansin-related mechanisms and contribute to future enhancement of maize grain yield.

Identification and characterization of the SET domain gene family in maize.

Histone lysine methylation plays a pivotal role in a variety of developmental and physiological processes through modifying chromatin structure and thereby regulating eukaryotic gene transcription. The SET domain proteins represent putative candidates for lysine methyltransferases containing the evolutionarily-conserved SET domain, and important epigenetic regulators present in eukaryotes. In recent years, increasing evidence reveals that SET domain proteins are encoded by a large multigene family in plants and investigation of the SET domain gene family will serve to elucidate the epigenetic mechanism diversity in plants. Although the SET domain gene family has been thoroughly characterized in multiple plant species including two model plant systems, Arabidopsis and rice, through their sequenced genomes, analysis of the entire SET domain gene family in maize was not completed following maize (B73) genome sequencing project. Here, we performed a genome-wide structural and evolutionary analysis of maize SET domain genes from the latest version of the maize (B73) genome. A complete set of 43 SET domain genes (Zmset1-43) were identified in the maize genome using Blast search tools and categorized into seven classes (Class I-VII) based on phylogeny. Chromosomal location of these genes revealed that they are unevenly distributed on all ten chromosomes with seven segmental duplication events, suggesting that segmental duplication played a key role in expansion of the maize SET domain gene family. EST expression data mining revealed that these newly identified genes had temporal and spatial expression pattern and suggested that many maize SET domain genes play functional developmental roles in multiple tissues. Furthermore, the transcripts of the 18 genes (the Class V subfamily) were detected in the leaves by two different abiotic stress treatments using semi-quantitative RT-PCR. The data demonstrated that these genes exhibited different expression levels in stress treatments. Overall, our study will serve to better understand the complexity of the maize SET domain gene family and also be beneficial for future experimental research to further unravel the mechanisms of epigenetic regulation in plants.

Genome-wide identification and expression profiling of DNA methyltransferase gene family in maize.

KEY MESSAGE: In this study, we identified eight DNA MTase genes in maize and the diversity of expression patterns of them was presented by EST mining, microarray and semi-quantitative expression profile analyses. DNA methylation plays a pivotal role in promoting genomic stability through diverse biological processes including regulation of gene expression during development and chromatin organization. Although this important biological process is mainly regulated by several conserved Cytosine-5 DNA methyltransferases encoded by a smaller multigene family in plants, investigation of the plant C5-MTase-encoding gene family will serve to elucidate the epigenetic mechanism diversity in plants. Recently, genome-wide identification and evolutionary analyses of the C5-MTase-encoding gene family have been characterized in multiple plant species including Arabidopsis, rice, carrot and wheat. However, little is known regarding the C5-MTase-encoding genes in the entire maize genome. Here, genome-wide identification and expression profile analyses of maize C5-MTase-encoding genes (ZmMETs) were performed from the latest version of the maize (B73) genome. Phylogenetic analysis indicated that the orthologs from the three species (maize, Arabidopsis and rice) were categorized into four classes. Chromosomal location of these genes revealed that they are unevenly distributed on 6 of all 10 chromosomes with three chromosomal/segmental duplication events, suggesting that gene duplication played a key role in expansion of the maize C5-MTase-encoding gene family. Furthermore, EST expression data mining, microarray data and semi-quantitative expression profile analyses detected in the leaves by two different abiotic stress treatments have demonstrated that these genes had temporal and spatial expression pattern and exhibited different expression levels in stress treatments, suggesting that functional diversification of ZmMET genes family. Overall, our study will serve to present signification insights to explore the plant C5-MTase-encoding gene expression and function and also be beneficial for future experimental research to further unravel the mechanisms of epigenetic regulation in plants.

Genome-wide identification and expression profiling of ankyrin-repeat gene family in maize.

Members of the ankyrin repeats (ANK) gene family encode ANK domain that are common in diverse organisms and play important roles in cell growth and development, such as cell-cell signal transduction and cell cycle regulation. Recently, genome-wide identification and evolutionary analyses of the ANK gene family have been carried out in Arabidopsis and rice. However, little is known regarding the ANK genes in the entire maize genome. In this study, we described the identification and structural characterization of 71 ANK genes in maize (ZmANK). Then, comprehensive bioinformatics analyses of ZmANK genes family were performed including phylogenetic, domain and motif analysis, chromosomal localization, intron/exon structural patterns, gene duplications and expression profiling. Domain composition analyses showed that ZmANK genes formed ten subfamilies. Five tandem duplications and 14 segmental duplications were identified in ZmANK genes. Furthermore, we took comparative analysis of the total ANK gene family in Arabidopsis, rice and maize, ZmANKs were more closely paired with OsANKs than with AtANKs. At last, expression profile analyses were performed. Forty-one members of ZmANK genes held EST sequences records. Semi-quantitative expression and microarray data analysis of these 41 ZmANK genes demonstrated that ZmANK genes exhibit a various expression pattern, suggesting that functional diversification of ZmANK genes family. The results will present significant insights to explore ANK genes expression and function in future studies in maize.

Effect of N-acetyl cysteine on enterocyte apoptosis and intracellular signalling pathways' response to oxidative stress in weaned piglets.

N-Acetyl cysteine (NAC) has been widely used for preventing reactive oxygen species-induced damage. However, little is known as to whether dietary NAC supplementation would alleviate intestinal injury in weaned piglets. The present study evaluated the effect of NAC on enterocyte apoptosis and intracellular signalling pathways' response to weaning stress. The control piglets were normally suckling, and piglets in the weaning and NAC groups were fed the basal diet and basal+NAC diet from 14 to 25 d of age, respectively. Compared with the control piglets, weaning increased cortisol concentrations (P< 0·05), decreased superoxide dismutase and glutathione peroxidase activities (P< 0·05), increased malondialdehyde content (P< 0·05) in serum and enhanced enterocyte apoptosis index (AI) and concentrations of caspase-3, caspase-8 and caspase-9 (P< 0·05). Gene expression analyses indicated that weaning induced apoptosis via Fas signalling and mitochondrial pathways in weaned piglets. Dietary NAC supplementation decreased (P< 0·05) cortisol concentrations and the AI, increased (P< 0·05) antioxidant status in serum and alleviated histopathological changes in the intestine. It also inhibited Fas, caspase-3, caspase-8 and integrin αvß6 (αvß6) gene expressions in the NAC-treated piglets. However, no significant decrease (P>0·10) in caspase-3, caspase-8 and caspase-9 concentrations was observed in the NAC group compared with the weaning group. In conclusion, weaning may induce enterocyte apoptosis via the activation of Fas-dependent and mitochondria-dependent apoptosis. Although NAC had no effect on caspase concentrations, it was clearly beneficial for preserving morphological integrity in weaned piglets via the regulation of cell apoptosis and the inhibition of Fas-dependent apoptosis and αvß6 expression.

Genome-wide analysis of the CCCH zinc finger gene family in Medicago truncatula.

KEY MESSAGE: In this study, we identified 34 CCCH Znf genes in Medicago truncatula and the results of semi-quantitative RT-PCR revealed that the expression patterns of subfamily VI members were diverse. CCCH-type zinc finger (Znf) proteins are specific transcriptional factors with a typical motif consisting of three cysteine residues and one histidine residue. Increasing evidences have revealed that CCCH Znf proteins participated in the regulation of plant growth, developmental processes and environmental responses. Survey and characterization of CCCH Znf genes in leguminous species would facilitate a better understanding of the evolutionary processes and functions of this gene family. In this study, we performed a comprehensive analysis of CCCH Znf genes in M. truncatula by describing the phylogenetic relationships, chromosomal location and gene structure of each family member. A total of 34 CCCH Znf genes were identified in the latest M. truncatula genome sequence. The 34 predicted members were clustered into nine subfamilies based on their phylogenetic analysis and structure features. In addition, the 34 Medicago CCCH Znf genes were found to be unevenly distributed on eight chromosomes. Furthermore, the expression profiles of subfamily VI were investigated under different stress conditions (PEG-6000, NaCl and ABA) by using semi-quantitative RT-PCR. The data showed that these genes displayed different expression levels in response to various stress conditions. The results presented in this study provide basic information about Medicago CCCH Znf genes and form a fundamental clue for cloning genes with specific functions in further studies and applications.

Downregulation of caffeoyl-CoA O-methyltransferase (CCoAOMT) by RNA interference leads to reduced lignin production in maize straw.

Lignin is a major cell wall component of vascular plants that provides mechanical strength and hydrophobicity to vascular vessels. However, the presence of lignin limits the effective use of crop straw in many agroindustrial processes. Here, we generated transgenic maize plants in which the expression of a lignin biosynthetic gene encoding CCoAOMT, a key enzyme involved in the lignin biosynthesis pathway was downregulated by RNA interference (RNAi). RNAi of CCoAOMT led to significantly downregulated expression of this gene in transgenic maize compared with WT plants. These transgenic plants exhibited a 22.4% decrease in Klason lignin content and a 23.3% increase in cellulose content compared with WT plants, which may reflect compensatory regulation of lignin and cellulose deposition. We also measured the lignin monomer composition of the RNAi plants by GC-MS and determined that transgenic plants had a 57.08% higher S/G ratio than WT plants. In addition, histological staining of lignin with Wiesner reagent produced slightly more coloration in the xylem and sclerenchyma than WT plants. These results provide a foundation for breeding maize with low-lignin content and reveal novel insights about lignin regulation via genetic manipulation of CCoAOMT expression.

Genome-wide analysis of the heat shock transcription factors in Populus trichocarpa and Medicago truncatula.

Research has provided substantial evidences that heat shock proteins (HSPs) play essential roles in extreme physiological conditions. Heat shock transcription factors (HSFs) are important HSPs regulators, but their functions are poorly understood, particularly in Populus and Medicago. In this study, a comprehensive bioinformatics analysis of the HSFs was performed in Populus trichocarpa and Medicago truncatula. Twenty-eight Populus HSFs and 16 Medicago HSFs were identified, and comparative analyzes of the two plants were carried out subsequently. HSFs were divided into three different classes and they were diverse and complicated transcription factors. The results of semi-quantitative RT-PCR in Populus suggested six genes (PtHSF-03, PtHSF-13, PtHSF-15, PtHSF-21, PtHSF-22 and PtHSF-23) were markedly increased by heat stress. The results presented here provide an important clue for cloning, expression and functional studies of the HSFs in Populus and Medicago.

Genome-wide survey and characterization of the WRKY gene family in Populus trichocarpa.

UNLABELLED: WRKY transcription factors participate in diverse physiological and developmental processes in plants. They have highly conserved WRKYGQK amino acid sequences in their N-termini, followed by the novel zinc-finger-like motifs, Cys2His2 or Cys2HisCys. To date, numerous WRKY genes have been identified and characterized in a number of herbaceous species. Survey and characterization of WRKY genes in a ligneous species would facilitate a better understanding of the evolutionary processes and functions of this gene family. In this study, 104 poplar WRKY genes (PtWRKY) were identified in the latest poplar genome sequence. According to their structural features, the predicted members were divided into the previously defined groups I-III, as described in rice. In addition, chromosomal localization of the genes demonstrated that there might be WRKY gene hot spots in 2.3 Mb regions on chromosome 14. Furthermore, approximately 83% (86 out of 104) WRKY genes participated in gene duplication events, including 69% (29 out of 42) gene pairs which exhibited segmental duplication. Using semi-quantitative RT-PCR, the expression patterns of subgroup III genes were investigated under different stresses [cold, drought, salinity and salicylic acid (SA)]. The data revealed that these genes presented different expression levels in response to various stress conditions. Expression analysis exhibited PtWRKY76 gene induced markedly in 0.1 mM SA or 25% PEG-6000 treatment. The results presented here provide a fundamental clue for cloning specific function genes in further studies and applications. KEY MESSAGE: This study identified 104 poplar WRKY genes and demonstrated WRKY gene hot spots on chromosome 14. Furthermore, semi-quantitative RT-PCR showed variable stress responses in subgroup III.