Secondary Metabolism Biosynthesis Research Articles

Genome-wide DNA methylation analysis of Metarhizium anisopliae during tick mimicked infection condition

BackgroundThe Metarhizium genus harbors important entomopathogenic fungi. These species have been widely explored as biological control agents, and strategies to improve the fungal virulence are under investigation. Thus, the interaction between Metarhizium species and susceptible hosts have been explored employing different methods in order to characterize putative virulence determinants. However, the impact of epigenetic modulation on the infection cycle of Metarhizium is still an open topic. Among the different epigenetic modifications, DNA methylation of cytosine bases is an important mechanism to control gene expression in several organisms. To better understand if DNA methylation can govern Metarhizium-host interactions, the genome-wide DNA methylation profile of Metarhizium anisopliae was explored in two conditions: tick mimicked infection and a saprophytic-like control.ResultsUsing a genome wide DNA methylation profile based on bisulfite sequencing (BS-Seq), approximately 0.60% of the total cytosines were methylated in saprophytic-like condition, which was lower than the DNA methylation level (0.89%) in tick mimicked infection condition. A total of 670 mRNA genes were found to be putatively methylated, with 390 mRNA genes uniquely methylated in the tick mimicked infection condition. GO terms linked to response to stimuli, cell wall morphogenesis, cytoskeleton morphogenesis and secondary metabolism biosynthesis were over-represented in the tick mimicked infection condition, suggesting that energy metabolism is directed towards the regulation of genes associated with infection. However, recognized virulence determinants known to be expressed at distinct infection steps, such as the destruxin backbone gene and the collagen-like protein gene Mcl1, were found methylated, suggesting that a dynamic pattern of methylation could be found during the infectious process. These results were further endorsed employing RT-qPCR from cultures treated or not with the DNA methyltransferase inhibitor 5-Azacytidine.ConclusionsThe set of genes here analyzed focused on secondary metabolites associated genes, known to be involved in several processes, including virulence. The BS-Seq pipeline and RT-qPCR analysis employing 5-Azacytidine led to identification of methylated virulence genes in M. anisopliae. The results provided evidences that DNA methylation in M. anisopliae comprises another layer of gene expression regulation, suggesting a main role of DNA methylation regulating putative virulence determinants during M. anisopliae infection cycle.

Comparative transcriptome profiling of different tissues from beta-carotene-enhanced transgenic soybean and its non-transgenic counterpart

Beta-carotene-enhanced transgenic soybeans, harboring genes encoding phytoene synthase and carotene desaturase under the control of a seed-specific promoter, were developed to alleviate vitamin A deficiency in populations, the diet of which was deficient in this vitamin. However, metabolic engineering of carotenoid biosynthetic pathways often has unintended effects, leading to major metabolic changes in plants that harbor endogenous beta-carotene biosynthesis pathways. In the present study, we performed transcriptome profiling analysis using RNA-seq to investigate the changes in the transcriptome and some unintended pleiotropic effects on the leaves, stems, roots, and seeds of beta-carotene-enhanced transgenic soybean lines, and compared them to those of their non-transgenic counterpart donor variety Kwangan. We observed that transgenic soybeans showed significant changes in secondary metabolic biosynthesis in leaves and down-regulated galactose metabolism in roots. Differentially expressed genes in the transgenic group, which were significantly up-regulated, included those encoding glycine-aspartic acid-serine-leucine-motif esterase/lipase, known as cutin synthase and cutinase. These results suggested enhanced beta-carotene biosynthesis may affect related enzymes to carbohydrate metabolism and fatty acid metabolism. Hence, we speculated that upregulation of cutin polymerization resulted in thickened seed coat and delayed seed germination of transgenic soybeans. Furthermore, downregulation of raffinose family oligosaccharide biosynthesis may cause redundancy of myo-inositol, a substrate of phytin formation. This could lead to phytic globoids accumulation in transgenic soybean seeds. The present imformation would be important for transgenic plant development via carotenoid metabolic engineering, with focus on beta-carotene over-production.

Tartary Buckwheat FtMYB31 Gene Encoding an R2R3-MYB Transcription Factor Enhances Flavonoid Accumulation in Tobacco

The R2R3-MYB transcription factors play an important role in regulating secondary metabolism biosynthesis and abiotic stress in plants. In this article, we report the identification of the transcription factor gene, FtMYB31, from the popular Eurasian crop tartary buckwheat (Fagopyrum tataricum) that enhances accumulation of the nutritionally beneficial compound rutin in transgenic tobacco leaves. The FtMYB31 complete cDNA coding sequence was isolated from the leaves of tartary buckwheat, and multiple protein sequence alignments and conserved domain analysis showed it contained a typical R2R3 MYB domain. Subcellular location experiments showed the FtMYB31 protein is localized in nucleus. The phylogenetic tree clustered FtMYB31 with VvMYBPA1 from Vitis vinifera, and AtMYB123 from Arabidopsis thaliana, belonging to the Subgroup 5 cluster. Comparison by qRT-PCR of FtMYB31 transcripts and those from rutin synthesis-related genes showed a relationship between FtMYB31, Ft4CL, and FtUFGT transcripts and rutin content in different tissues of F. tataricum, with correlation coefficients of − 0.68, 0.69, and 0.47, respectively. Transgenic experiments indicated that FtMYB31 upregulated CHS, F3H, and FLS genes in transgenic tobacco and enhanced the accumulation of rutin and total flavonols. These results suggest that FtMYB31 encodes an R2R3-MYB transcription factor that positively regulates flavonol biosynthesis in tartary buckwheat and tobacco and is a possible target for genetically modifying tartary buckwheat to enhance the content of beneficial compounds such as rutin.

Control of Development, Secondary Metabolism and Light-Dependent Carotenoid Biosynthesis by the Velvet Complex of Neurospora crassa.

Neurospora crassa is an established reference organism to investigate carotene biosynthesis and light regulation. However, there is little evidence of its capacity to produce secondary metabolites. Here, we report the role of the fungal-specific regulatory velvet complexes in development and secondary metabolism (SM) in N. crassa Three velvet proteins VE-1, VE-2, VOS-1, and a putative methyltransferase LAE-1 show light-independent nucleocytoplasmic localization. Two distinct velvet complexes, a heterotrimeric VE-1/VE-2/LAE-1 and a heterodimeric VE-2/VOS-1 are found in vivo The heterotrimer-complex, which positively regulates sexual development and represses asexual sporulation, suppresses siderophore coprogen production under iron starvation conditions. The VE-1/VE-2 heterodimer controls carotene production. VE-1 regulates the expression of >15% of the whole genome, comprising mainly regulatory and developmental features. We also studied intergenera functions of the velvet complex through complementation of Aspergillus nidulans veA, velB, laeA, vosA mutants with their N. crassa orthologs ve-1, ve-2, lae-1, and vos-1, respectively. Expression of VE-1 and VE-2 in A. nidulans successfully substitutes the developmental and SM functions of VeA and VelB by forming two functional chimeric velvet complexes in vivo, VelB/VE-1/LaeA and VE-2/VeA/LaeA, respectively. Reciprocally, expression of veA restores the phenotypes of the N. crassa ve-1 mutant. All N. crassa velvet proteins heterologously expressed in A. nidulans are localized to the nuclear fraction independent of light. These data highlight the conservation of the complex formation in N. crassa and A. nidulans However, they also underline the intergenera similarities and differences of velvet roles according to different life styles, niches and ontogenetic processes.

A label-free proteomic approach differentiates between conventional and organic rice

Rice is a major cereal in the food industry. In this study, a quantitative label-free proteomic characterization of the organic rice proteome was performed; the proteome was compared to its conventional counterparts. As a result, a total of 114 proteins were significantly changed between the organic and conventional rice samples. Among them, 56 proteins were regarded as upregulated proteins and 58 were downregulated proteins in organic cultivated samples. Molecular function and bioinformatics analyses indicated that changes in the biosynthesis of secondary metabolites, metabolic pathways, and microbial metabolism in diverse environments contributed to the differences. These results were confirmed through the identification of 20 significantly changed metabolites. Specifically, these proteins mainly corresponded to carbohydrate metabolism, ribosome biogenesis, and the stress response. This in-depth study of proteins in rice extracts has implicated the role of those metabolic cycles involved in planting patterns, and represents a starting point in the selection of key proteins for rice authentication in the food industry.

A Comprehensive Analysis of the Small GTPases Ypt7 Involved in the Regulation of Fungal Development and Secondary Metabolism in Monascus ruber M7.

Ypts (yeast protein transports),also called as ras-associated binding GTPases (Rab), are the largest group of the small GTPases family, which have been extensively studied in model eukaryotic cells and play a pivotal role in membane trafficking, while this study showed potential regulation role of Ypts in fungi. One of Ypts, Ypt7 may be involved in fungal development and secondary metabolism, but the exact mechanism still exists a controversy. In current study, the functions of a Monascus ypt7 homologous gene (mrypt7) from Monascus ruber M7 was investigated by combination of gene-deletion (Δmrypt7), overexpression (M7::PtrpC-mrypt7) and transcriptome analysis. Results showed that the radial growth rate of Δmrypt7 was significantly slower than M. ruber M7, little conidia and ascospores can be observed in Δmrypt7, but the yield of intracellular secondary metabolites was dramatically increased. Simultaneously, the mrypt7 overexpression strain possessed similar capacity for sporulation and secondary metabolism observed in M. ruber M7. Transcriptome results further illustrated that mrypt7 could coordinate with numerous genes involved in the vegetative growth, conidiogenesis, secondary metabolism biosynthesis and transportation of M. ruber M7. Combined with the similar effect of Ypt7 homologs on other fungi, we propose that Ypt7 works more like a global regulatory factor in fungi. To our knowledge, it is the first time to investigate Ypt7 functions in Monascus. It could also improve the understanding of Ypt7 functions in fungi.

Extensive Post-Transcriptional Regulation Revealed by Transcriptomic and Proteomic Integrative Analysis in Cassava under Drought.

Cassava is a major tropical/subtropical food crop and its yield is greatly restrained by drought; however, the mechanism underlying the drought stress remains largely unknown. In this study, totally 1242 and 715 differentially expressed genes (DEGs), together with 237 and 307 differentially expressed proteins (DEPs), were respectively identified in cassava leaves and roots through RNA-seq and iTRAQ techniques. The majority of DEGs and DEPs were exclusively regulated at the mRNA and protein level, respectively, whereas only a few were commonly regulated, indicating the major involvement of post-transcriptional regulation under drought. Subsequently, the functions of these specifically or commonly regulated DEGs and DEPs were analyzed, and the post-transcriptional regulation of genes involved in heat shock protein, secondary metabolism biosynthesis, and hormone biosynthesis was extensively discussed. This is the first report on an integration of transcriptomic and proteomic analysis in cassava, and it provides new insights into the post-transcriptional regulation of cassava drought stress.

Physiological and Transcriptomic Analysis of Tree Peony (Paeonia section Moutan DC.) in Response to Drought Stress

Tree peony (Paeonia section Moutan DC.) is a famous ornamental plant, and P. ostii has been used for seed oil production in China because it is rich in α-linolenic acid. P. ostii has some resistance to drought, but lack of water can severely hinder its growth and development in arid areas. In order to clarify drought stress induced physiological and molecular changes of P. ostia, its physiological and transcriptomic analyses were performed under drought stress, and we found that P. ostii leaves drooped significantly 12 days after treatment and observed a significant increase in all detected physiological indices in response to drought treatment except leaf water content, chlorophyll, and carotenoid content. Meanwhile, the activity of three antioxidant enzymes basically increased under drought treatment. Moreover, drought treatment significantly reduced photosynthetic and chlorophyll fluorescence parameters except non-photochemical quenching (qN), and maintained more intact mesophyll cell structures. Additionally, many differentially expressed genes (DEGs) were found by transcriptome sequencing, which play an important role in P. ostia drought tolerance by controlling a variety of biological processes, including the reactive oxygen species (ROS) system, chlorophyll degradation and photosynthetic competency, fatty acid metabolism, proline metabolism, biosynthesis of secondary metabolism, and plant hormone metabolism. These results provide a better understanding of P. ostii responses to drought stress.

Transcriptomic and proteomic effects of (-)-epigallocatechin 3-O-(3-O-methyl) gallate (EGCG3”Me) treatment on ethanol-stressed Saccharomyces cerevisiae cells

Saccharomyces cerevisiae (S. cerevisiae) is the main fermentation strain in brewing industry. However, the accumulation of ethanol during the fermentation inhibits the growth of S. cerevisiae. Polyphenols are important bioactive ingredients in oolong tea, and epigallocatechin-3-O-(3”-O-methyl)-gallate (EGCG3”Me) has exhibited ameliorate effect on alcohol intoxication. Therefore, in the current work, we used RNA-seq transcriptomics and iTRAQ proteomic analysis to study the effect of EGCG3”Me on ethanol-stressed S. cerevisiae. After EGCG3”Me intervention (0.8%, w/v), 178 up-regulated and 172 down-regulated genes were identified, meanwhile, 190 differentially expressed proteins (DEPs) were identified. In addition, KEGG pathways for metabolic pathways, biosynthesis of secondary metabolites and microbial metabolism were among the most DEPs after EGCG3”Me intervention. The integrated transcriptomic and proteomic analysis indicated EGCG3”Me may alleviate ethanol-induced damage on the cell wall and cell membrane of S. cerevisiae, and facilitate the redox balance and glycolysis. This study provides new insights into the mechanisms underlying the molecular response to ethanol in S. cerevisiae by the treatment of EGCG3”Me.

Proteomic analysis of the rice (Oryza officinalis) provides clues on molecular tagging of proteins for brown planthopper resistance

BackgroundAmong various pests, the brown planthopper (BPH) that damages rice is the major destructive pests. Understanding resistance mechanisms is a critical step toward effective control of BPH. This study investigates the proteomics of BPH interactions with three rice cultivars: the first resistant (PR) to BPH, the second susceptible (PS), and the third hybrid (HR) between the two, in order to understand mechanisms of BPH resistance in rice.ResultsOver 4900 proteins were identified from these three rice cultivars using iTRAQ proteomics study. A total of 414, 425 and 470 differentially expressed proteins (DEPs) were detected from PR, PS and HR, respectively, after BPH infestation. Identified DEPs are mainly enriched in categories related with biosynthesis of secondary metabolites, carbon metabolism, and glyoxylate and dicarboxylate metabolism. A two-component response regulator protein (ORR22) may participate in the early signal transduction after BPH infestation. In the case of the resistant rice cultivar (PR), 6 DEPs, i.e. two lipoxygenases (LOXs), a lipase, two dirigent proteins (DIRs) and an Ent-cassa-12,15-diene synthase (OsDTC1) are related to inheritable BPH resistance. A heat shock protein (HSP20) may take part in the physiological response to BPH infestation, making it a potential target for marker-assisted selection (MAS) of rice. Quantitative real-time polymerase chain reaction (qRT-PCR) revealed eight genes encoding various metabolic proteins involved in BPH resistance. During grain development the expressions of these genes varied at the transcriptional and translational levels.ConclusionsThis study provides comprehensive details of key proteins under compatible and incompatible interactions during BPH infestation, which will be useful for further investigation of the molecular basis of rice resistance to BPH and for breeding BPH-resistant rice cultivars.

Composition and Predictive Functional Analysis of Rhizosphere Bacterial Communities in Riparian Buffer Strips in the Danjiangkou Reservoir, China

Microbial communities play crucial roles in the global biogeochemical nitrogen cycle. To our knowledge, the compositions and functions of rhizosphere communities in riparian buffer strips have not been reported. In this study, rhizosphere soil samples were collected from herbs (Vetiveria zizanioides and Phragmites australis), trees (Pyrus betulifolia), and shrubs (Discocleidion rufescens) in the Danjiangkou Reservoir in June 2017. High-throughput sequencing was performed to analyze the community structure and diversity of bacteria. Phylogenetic analysis based on 16S rDNA sequences shows that the bacterial communities can be divided into 31 major phylogenetic groups. The dominant phylogenetic groups include Proteobacteria, Bacteroidetes, Actinobacteria, Gemmatimonadetes, and Acidobacteria. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) was used to determine the metabolic and functional abilities of the observed bacterial communities. Our results reveal a wide genetic diversity of organisms involved in various essential processes such as biosynthesis of other secondary metabolites, transcription, Glycan biosynthesis and metabolism, cell growth and death, and carbohydrate metabolism. Based on the 16S rRNA gene copy number of the detected phylotype, the bacterial rhizospheres of plants in riparian buffer strips can be ranked as follows:Discocleidion rufescens > Phragmites australis > Vetiveria zizanioides > Pyrus betulifolia. We analyzed the differences of different plants from the perspective of bacterial community composition and function and provide a foundation for vegetation construction and water environmental protection in riparian buffer strips of the Danjiangkou Reservoir.

Functional analysis of Leifsonia xyli subsp. xyli membrane protein gene Lxx18460 (anti-sigma K)

BackgroundSugarcane is an important sugar and economic crop in the world. Ratoon stunting Disease (RSD) of sugarcane, caused by Leifsonia xyli subsp. xyli, is widespread in countries and regions where sugarcane is grown and also limited to sugarcane productivity. Although the whole genome sequencing of Leifsonia xyli subsp. xyli was completed, progress in understanding the molecular mechanism of the disease has been slow because it is difficult to grow in culture.ResultsThe Leifsonia xyli subsp. xyli membrane protein gene Lxx18460 (anti-sigma K) was cloned from the Lxx-infected sugarcane cultivar GT11 at the mature stage using RT-PCR technique, and the gene structure and expression in infected sugarcane were analyzed. The Lxx18460 gene was transformed into Nicotiana tabacum by Agrobacterium tumefaciens-mediation. The transgenic tobacco plants overexpressing Lxx18460 had lower levels in plant height, leaf area, net photosynthetic rate and endogenous hormones of IAA, ABA and GA3, as well as lower activities of three antioxidant enzymes, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) than the wild type (WT) tobacco. With the plant growth, the expression of Lxx18460 gene and protein was increased. To better understand the regulation of Lxx18460 expression, transcriptome analysis of leaves from transgenic and wild type tobacco was performed. A total of 60,222 all-unigenes were obtained through BGISEQ-500 sequencing. Compared the transgenic plants with the WT plants, 11,696 upregulated and 5949 downregulated genes were identified. These differentially expressed genes involved in many metabolic pathways including signal transduction, biosynthesis of other secondary metabolism, carbohydrate metabolism and so on. Though the data presented here are from a heterologous system, Lxx 18460 has an adverse impact on the growth of tobacco; it reduces the photosynthesis of tobacco, destroys the activity of defense enzymes, and affects the levels of endogenous hormones, which indicate that Lxx18460 may act important roles in the course of infection in sugarcane.ConclusionsThis is the first study on analyzing the function of the membrane protein gene Lxx18460 of anti-sigma K (σK) factor in Leifsonia xyli subsp. xyli. Our findings will improve the understanding of the interaction between the RSD pathogen Leifsonia xyli subsp. xyli and sugarcane. The output of this study will also be helpful to explore the pathogenesis of RSD.

RNA sequencing-based transcriptome analysis of mature strawberry fruit infected by necrotrophic fungal pathogen Botrytis cinerea

Botrytis cinerea, the causal agent of gray mold disease, is regarded as the most impactful postharvest fungal pathogen, as it causes serious losses in fresh fruits, ornamentals, and vegetables worldwide. To understand the molecular defense mechanisms of the affected plants, we analyzed transcriptome using RNA sequencing (RNA-seq) of mature strawberry fruit that were infected by B. cinerea at 12, 24, and 48 h. Overall, 18 cDNA libraries were produced generating 923,482,642,150 base pair reads. A total of 1459 differentially expressed genes (DEGs) were identified (≥2.0-fold change and FDR ≤ 0.05), among which only 26 were down-regulated. The majority of changes in gene expression occurred 24 h after inoculation, before significant lesion development, suggesting that this is an important stage during B. cinerea infection. Further analysis revealed that the DEGs were predominately involved in pathogen recognition (pattern recognition receptors), signaling transduction (MAPK cascades, CDPKs), defense response (transcription factors, secondary metabolism biosynthesis, pathogenis-related), as well as different sorts of transporter encoding genes. These data provided a global insight into mature strawberry fruit-B. cinerea interaction and might be used for fruit postharvest pathogens and diseases management.

Transcriptome Analyses from Mutant Salvia miltiorrhiza Reveals Important Roles for SmGASA4 during Plant Development.

Salvia miltiorrhiza (S. miltiorrhiza) is an important Chinese herb that is derived from the perennial plant of Lamiaceae, which has been used to treat neurasthenic insomnia and cardiovascular disease. We produced a mutant S. miltiorrhiza (MT), from breeding experiments, that possessed a large taproot, reduced lateral roots, and defective flowering. We performed transcriptome profiling of wild type (WT) and MT S. miltiorrhiza using second-generation Illumina sequencing to identify differentially expressed genes (DEGs) that could account for these phenotypical differences. Of the DEGs identified, we investigated the role of SmGASA4, the expression of which was down-regulated in MT plants. SmGASA4 was introduced into Arobidopsis and S. militiorrhiza under the control of a CaMV35S promoter to verify its influence on abiotic stress and S. miltiorrhiza secondary metabolism biosynthesis. SmGASA4 was found to promote flower and root development in Arobidopsis. SmGASA4 was also found to be positively regulated by Gibberellin (GA) and significantly enhanced plant resistance to salt, drought, and paclobutrazol (PBZ) stress. SmGASA4 also led to the up-regulation of the genes involved in salvianolic acid biosynthesis, but inhibited the expression of the genes involved in tanshinone biosynthesis. Taken together, our results reveal SmGASA4 as a promising candidate gene to promote S. miltiorrhiza development.

Transcriptome Analyses in Different Cucumber Cultivars Provide Novel Insights into Drought Stress Responses.

Drought stress is one of the most serious threats to cucumber quality and yield. To gain a good understanding of the molecular mechanism upon water deficiency, we compared and analyzed the RNA sequencing-based transcriptomic responses of two contrasting cucumber genotypes, L-9 (drought-tolerant) and A-16 (drought-sensitive). In our present study, combining the analysis of phenotype, twelve samples of cucumber were carried out a transcriptomic profile by RNA-Seq under normal and water-deficiency conditions, respectively. A total of 1008 transcripts were differentially expressed under normal conditions (466 up-regulated and 542 down-regulated) and 2265 transcripts under drought stress (979 up-regulated and 1286 down-regulated). The significant positive correlation between RNA sequencing data and a qRT-PCR analysis supported the results found. Differentially expressed genes (DEGs) involved in metabolic pathway and biosynthesis of secondary metabolism were significantly changed after drought stress. Several genes, which were related to sucrose biosynthesis (Csa3G784370 and Csa3G149890) and abscisic acid (ABA) signal transduction (Csa4M361820 and Csa6M382950), were specifically induced after 4 days of drought stress. DEGs between the two contrasting cultivars identified in our study provide a novel insight into isolating helpful candidate genes for drought tolerance in cucumber.

Jasmonate signalling pathway in strawberry: Genome-wide identification, molecular characterization and expression of JAZs and MYCs during fruit development and ripening.

Jasmonates (JAs) are signalling molecules involved in stress responses, development and secondary metabolism biosynthesis, although their roles in fleshy-fruit development and ripening processes are not well known. In strawberry fruit, it has been proposed that JAs could regulate the early development through the activation of the JAs biosynthesis. Moreover, it has been reported that JA treatment increases anthocyanin content in strawberry fruit involving the bioactive jasmonate biosynthesis. Nevertheless, JA signalling pathway, of which main components are the COI1-JAZ co-receptor and the MYC transcription factors (TFs), has not been characterized in strawberry until now. Here we identified and characterized the woodland strawberry (Fragaria vesca) JAZ and MYC genes as well as studied their expression during development and ripening stages in commercial strawberry (Fragaria × ananassa) fruit. We described twelve putative JAZ proteins and two MYC TFs, which showed high conservation with respect to their orthologs in Arabidopsis thaliana and in other fleshy-fruit species such as Malus × domestica, Vitis vinifera and Solanum lycopersicum as revealed by gene synteny and phylogenetic analyses. Noteworthy, their expression levels exhibited a significant decrease from fruit development to ripening stages in F. × ananassa, along with others of the JA signalling-related genes such as FaNINJA and FaJAMs, encoding for negative regulators of JA responses. Moreover, we found that main JA signalling-related genes such as FaMYC2, and FaJAZ1 are promptly induced by JA treatment at early times in F. × ananassa fruit. These results suggest the conservation of the canonical JA signalling pathway in strawberry and a possible role of this pathway in early strawberry fruit development, which also correlates negatively with the beginning of the ripening process.

Distinct Roles of Velvet Complex in the Development, Stress Tolerance, and Secondary Metabolism in Pestalotiopsis microspora, a Taxol Producer.

The velvet family proteins have been shown to play critical roles in fungal secondary metabolism and development. However, variations of the roles have been observed in different fungi. We report here the observation on the role of three velvet complex components VeA, VelB, and LaeA in Pestalotiopsis microspora, a formerly reported taxol-producing fungus. Deletion of individual members led to the retardation of vegetative growth and sporulation and pigmentation, suggesting critical roles in these processes. The mutant strain △velB appeared hypersensitive to osmotic stress and the dye Congo red, whereas △veA and △laeA were little affected by the pressures, suggesting only velB was required for the integrity of the cell wall. Importantly, we found that the genes played distinct roles in the biosynthesis of secondary metabolites in P. microspora. For instance, the production of pestalotiollide B, a previously characterized polyketide, required velB and laeA. In contrast, the veA gene appeared to inhibit the pestalotiollide B (PB) role in its biosynthesis. This study suggests that the three components of the velvet complex are important global regulators, but with distinct roles in hyphal growth, asexual production, and secondary metabolism in P. microspora. This work provides information for further understanding the biosynthesis of secondary metabolism in the fungus.

Complete Genome Sequence of Dietzia sp. Strain WMMA184, a Marine Coral-Associated Bacterium.

ABSTRACTDietzia sp. strain WMMA184 was isolated from the marine coral Montastraea faveolata as part of ongoing drug discovery efforts. Analysis of the 4.16-Mb genome provides information regarding interspecies interactions as it pertains to the regulation of secondary metabolism and natural product biosynthesis potential.

Transcription profiling analysis of genes and pathomechanisms underlying the defense response against Tobacco Etch Virus infection in Arabidopsis thaliana

The aim of this study was to identify potential genes and mechanisms in Arabidopsis thaliana (L.) Heynh. in response to Tobacco Etch Virus (TEV) infection by bioinformatics methods. The transcription profile GSE37269 containing 28 TEV-At17b infected and 25 non-infected samples of A. thaliana was downloaded and used. Limma software in R language was used to identify differentially expressed genes (DEGs) between mock and infected samples, and Gene Ontology and pathway enrichment analysis of DEGs were performed. Protein-protein interaction (PPI) network was constructed by STRING database. Moreover, a weighted gene co-expression network of closely co-expressed DEGs was constructed. Total 1781 DEGs including 873 up-regulated and 908 down-regulated genes were obtained. Up-regulated DEGs were mainly enriched in response to reactive oxygen species, and phenylalanine metabolism as well as biosynthesis of phenylpropanoids, while down-regulated DEGs were mainly enriched in external encapsulating structure organization. Up-regulated genes of AT2G18690 and AT1G19020, down-regulated gene of LAC11 (laccase 11) and IRX12 (iroquois homeobox 12) were hub nodes in PPI network. A significant co-expressed module containing AT5G37485, AT4G36430 and ATH8 (thioredoxin H-type 8) was identified and genes of it were significantly enriched in cellular response to reactive oxygen species and oxidative stress. AT4G36430 and ATH8 in the response to hydrogen peroxide and oxidative stress, and some peroxidase-like genes in the secondary metabolic and phenylpropanoid biosynthesis, may be responsible for the antiviral response to TEV-At17b infection in A. thaliana.

Recent advances on the molecular aspects of ochratoxin A biosynthesis

Recently, studies on the molecular aspects of ochratoxin A biosynthesis have significantly advanced. Differently from other mycotoxins, the genes and the enzymatic stages involved in biosynthesis pathway of ochratoxin A have remained long unknown. New ecological data have led to the definition of new producing species, responsible of ochratoxin A contamination in several food and feed. In parallel, genomics, transcriptomics and proteomics studies have provided new information to better define the molecular key steps of the mycotoxin biosynthesis. Further studies are still needed to completely clarify the regulatory mechanisms underlying the activation of the production of ochratoxin A. Previous findings on fungal secondary metabolism biosynthesis and the availability of new data from different omics approaches will permit to fill the gap of knowledge in the near future.