Biosynthesis of triacylglycerols (tags) in plants and algae

Triacylglycerols (TAGs), which consist of three fatty acids bound to a glycerol backbone, are major storage lipids that accumulate in developing seeds, flower petals, pollen grains, and fruits of innumerous plant species. These storage lipids are of great nutritional and nutraceutical value and, thus, are a common source of edible oils for human consumption and industrial purposes. Two metabolic pathways for the production of TAGs have been clarified: an acyl CoA-dependent pathway and an acyl-CoA-independent pathway. Lipid metabolism, specially the pathways to fatty acids and TAG biosynthesis, is relatively well understood in plants, but poorly known in algae. It is generally accepted that the basic pathways of fatty acid and TAG biosynthesis in algae are analogous to those of higher plants. However, unlike higher plants where individual classes of lipids may be synthesized and localized in a specific cell, tissue or organ, the complete pathway, from carbon dioxide fixation to TAG synthesis and sequestration, takes place within a single algal cell. Another distinguishing feature of some algae is the large amounts of very long-chain polyunsaturated fatty acids (VLC-PUFAs) as major fatty acid components. Nowadays, the focus of attention in biotechnology is the isolation of novel fatty acid metabolizing genes, especially elongases and desaturases that are responsible for PUFAs synthesis, from different species of algae, and its transfer to plants. The aim is to boost the seed oil content and to generate desirable fatty acids in oilseed crops through genetic engineering approaches. This paper presents the current knowledge of the neutral storage lipids in plants and algae from fatty acid biosynthesis to TAG accumulation

Secondary metabolite gene clusters in the entomopathogen fungus Metarhizium anisopliae : genome identification and patterns of expression in a cuticle infection model

Background: The described species from the Metarhizium genus are cosmopolitan fungi that infect arthropod hosts. Interestingly, while some species infect a wide range of hosts (host-generalists), other species infect only a few arthropods (host-specialists). This singular evolutionary trait permits unique comparisons to determine how pathogens and virulence determinants emerge. Among the several virulence determinants that have been described, secondary metabolites (SMs) are suggested to play essential roles during fungal infection. Despite progress in the study of pathogen-host relationships, the majority of genes related to SM production in Metarhizium spp. are uncharacterized, and little is known about their genomic organization, expression and regulation. To better understand how infection conditions may affect SM production in Metarhizium anisopliae, we have performed a deep survey and description of SM biosynthetic gene clusters (BGCs) in M. anisopliae, analyzed RNA-seq data from fungi grown on cattle-tick cuticles, evaluated the differential expression of BGCs, and assessed conservation among the Metarhizium genus. Furthermore, our analysis extended to the construction of a phylogeny for the following three BGCs: a tropolone/citrinin-related compound (MaPKS1), a pseurotin-related compound (MaNRPS-PKS2), and a putative helvolic acid (MaTERP1). Results: Among 73 BGCs identified in M. anisopliae, 20 % were up-regulated during initial tick cuticle infection and presumably possess virulence-related roles. These up-regulated BGCs include known clusters, such as destruxin, NG39x and ferricrocin, together with putative helvolic acid and, pseurotin and tropolone/citrinin-related compound clusters as well as uncharacterized clusters. Furthermore, several previously characterized and putative BGCs were silent or down-regulated in initial infection conditions, indicating minor participation over the course of infection. Interestingly, several up-regulated BGCs were not conserved in host-specialist species from the Metarhizium genus, indicating differences in the metabolic strategies employed by generalist and specialist species to overcome and kill their host. These differences in metabolic potential may have been partially shaped by horizontal gene transfer (HGT) events, as our phylogenetic analysis provided evidence that the putative helvolic acid cluster in Metarhizium spp. originated from an HGT event. Conclusions: Several unknown BGCs are described, and aspects of their organization, regulation and origin are discussed, providing further support for the impact of SM on the Metarhizium genus lifestyle and infection process

Mycoplasma non-coding RNA: identification of small RNAs and targets

Background: Bacterial non-coding RNAs act by base-pairing as regulatory elements in crucial biological processes. We performed the identification of trans-encoded small RNAs (sRNA) from the genomes of Mycoplama hyopneumoniae, Mycoplasma flocculare and Mycoplasma hyorhinis, which are Mycoplasma species that have been identified in the porcine respiratory system. Results: A total of 47, 15 and 11 putative sRNAs were predicted in M. hyopneumoniae, M. flocculare and M. hyorhinis, respectively. A comparative genomic analysis revealed the presence of species or lineage specific sRNA candidates. Furthermore, the expression profile of some M. hyopneumoniae sRNAs was determined by a reverse transcription amplification approach, in three different culture conditions. All tested sRNAs were transcribed in at least one condition. A detailed investigation revealed a differential expression profile for two M. hyopneumoniae sRNAs in response to oxidative and heat shock stress conditions, suggesting that their expression is influenced by environmental signals. Moreover, we analyzed sRNA-mRNA hybrids and accessed putative target genes for the novel sRNA candidates. The majority of the sRNAs showed interaction with multiple target genes, some of which could be linked to pathogenesis and cell homeostasis activity. Conclusion: This study contributes to our knowledge of Mycoplasma sRNAs and their response to environmental changes. Furthermore, the mRNA target prediction provides a perspective for the characterization and comprehension of the function of the sRNA regulatory mechanisms

Correlation between female sex, IL28B genotype, and the clinical severity of bronchiolitis in pediatric patients

Background: Single-nucleotide polymorphisms (SNPs) that impact on the differential expression of interleukin 28B (IL28B) are implicated in the progression of viral-induced diseases. In this prospective longitudinal cohort study, we evaluated the association between IL28B SNPs rs12979860 and rs8099917 and the clinical outcome of bronchiolitis in pediatric patients. Methods: A total of 682 infants suffering from bronchiolitis, categorized based on the final clinical outcome as mild or severe, were genotyped for IL28B SNPs rs12979860 and rs8099917. Results: When infants were categorized exclusively based on the final clinical outcome, no association was established between IL28B SNPs and the severity of bronchiolitis. However, when stratified by sex, the homozygotes for the minor alleles of rs12979860 (T) and rs8099917 (G) were associated with a mild disease in girls but not in boys. Conclusion: SNPs rs12979860 and rs8099917 correlate with the severity of bronchiolitis and display a sex bias, where GG rs8099917 and TT rs12979860 genotypes are associated with a mild disease in girls but not in boys. These findings suggest that innate immunity and female sex links with the outcome of the diseases induced by respiratory viruses, such as RSV. © 2019, International Pediatric Research Foundation, Inc.Indexación: Scopu

Genome-wide diversity and differentiation in New World populations of the human malaria parasite Plasmodium vivax.

BACKGROUND: The Americas were the last continent colonized by humans carrying malaria parasites. Plasmodium falciparum from the New World shows very little genetic diversity and greater linkage disequilibrium, compared with its African counterparts, and is clearly subdivided into local, highly divergent populations. However, limited available data have revealed extensive genetic diversity in American populations of another major human malaria parasite, P. vivax. METHODS: We used an improved sample preparation strategy and next-generation sequencing to characterize 9 high-quality P. vivax genome sequences from northwestern Brazil. These new data were compared with publicly available sequences from recently sampled clinical P. vivax isolates from Brazil (BRA, total n = 11 sequences), Peru (PER, n = 23), Colombia (COL, n = 31), and Mexico (MEX, n = 19). PRINCIPAL FINDINGS/CONCLUSIONS: We found that New World populations of P. vivax are as diverse (nucleotide diversity π between 5.2 × 10-4 and 6.2 × 10-4) as P. vivax populations from Southeast Asia, where malaria transmission is substantially more intense. They display several non-synonymous nucleotide substitutions (some of them previously undescribed) in genes known or suspected to be involved in antimalarial drug resistance, such as dhfr, dhps, mdr1, mrp1, and mrp-2, but not in the chloroquine resistance transporter ortholog (crt-o) gene. Moreover, P. vivax in the Americas is much less geographically substructured than local P. falciparum populations, with relatively little between-population genome-wide differentiation (pairwise FST values ranging between 0.025 and 0.092). Finally, P. vivax populations show a rapid decline in linkage disequilibrium with increasing distance between pairs of polymorphic sites, consistent with very frequent outcrossing. We hypothesize that the high diversity of present-day P. vivax lineages in the Americas originated from successive migratory waves and subsequent admixture between parasite lineages from geographically diverse sites. Further genome-wide analyses are required to test the demographic scenario suggested by our data

MicroRNAs play critical roles during plant development and in response to abiotic stresses

MicroRNAs (miRNAs) have been identified as key molecules in regulatory networks. The fine-tuning role of miRNAs in addition to the regulatory role of transcription factors has shown that molecular events during development are tightly regulated. In addition, several miRNAs play crucial roles in the response to abiotic stress induced by drought, salinity, low temperatures, and metals such as aluminium. Interestingly, several miRNAs have overlapping roles with regard to development, stress responses, and nutrient homeostasis. Moreover, in response to the same abiotic stresses, different expression patterns for some conserved miRNA families among different plant species revealed different metabolic adjustments. The use of deep sequencing technologies for the characterisation of miRNA frequency and the identification of new miRNAs adds complexity to regulatory networks in plants. In this review, we consider the regulatory role of miRNAs in plant development and abiotic stresses, as well as the impact of deep sequencing technologies on the generation of miRNA data

Caracterização filogenética das proteínas inativadoras de ribossomos (RIPs) de mamona (Ricinus communis L.) e análise da expressão dos genes Rcom RIPs durante o desenvolvimento da semente

As Proteínas Inativadoras de Ribossomos (RIPs) compreendem uma família de enzimas que inibem a síntese protéica através da depurinação de uma adenina específica do RNA ribossomal. Os membros desta família são classificados como RIPs do tipo I, quando possuem somente o RNA-N-Glicosidase e RIPs do tipo II quando além do domínio glicosidase, também apresentam um domínio de lectina. As RIPs foram mais estudadas em plantas, onde a ricina e a aglutinina, ambas RIP do tipo II de mamona (Ricinus communis), estão entre as primeiras descritas. O presente trabalho teve o objetivo de identificar parálogos da ricina e aglutinina, bem como RIPs do tipo I de mamona e analisar as suas relações filogenéticas. Além disso, validar o uso de 14 potenciais genes de referência para qRT-PCR em cinco estádios do desenvolvimento da semente de mamona. O padrão de expressão gênica por RT-qPCR de todas RIPs de mamona identificadas, também foram analisados nestes mesmos estádios. Um total de 18 genes de RIPs foi identificado em mamona (Rcom RIPs), dos quais 10 foram classificados como do tipo II e 8 do tipo I. As topologias das árvores filogenéticas sugerem que as Rcom RIPs foram originadas a partir de múltiplos eventos de duplicação gênica. Dois modelos evolutivos foram propostos para a radiação das Rcom RIPs, baseados em processos de fusão gênica associado ou não a eventos de duplicação parcial. Os genes Act 2/7, EF β, Ubi, TIP e UBC foram os que apresentaram perfil de expressão mais estável e foram selecionados para subsequente normalização dos dados de expressão das Rcom RIPs. Os genes que codificam as Rcom RIPI 3, 4, 5, 7 e 8 e as Rcom RIPII 1, 2, 4, 5, 6 e 8 são transcritos em sementes, sendo que a Rcom RIPII 1 (ricina) e a Rcom RIPII 2 (aglutinina) foram as mais expressas. O presente trabalho apresenta um modelo evolutivo das Rcom RIPs, o qual pode ser extrapolado para outras espécies de plantas. Este trabalho também demonstra o primeiro esforço para a padronização de genes de referência para RT-qPCR em mamona e o primeiro que apresenta a expressão outras Rcom RIPs, além da ricina e aglutinina.Ribosome inactivating proteins (RIPs) comprise a family of enzymes that inhibit protein synthesis, after depurination of an adenine-specific ribosomal RNA. The members of this family are classified as type I RIPs, which have a RNA-Nglycosidase domain and type II RIPs encompassing a RNA-N-glycosidase and a lectin domain.The RIPs were more studied in plants, where ricin and agglutinin, both type II RIP of castor bean (Ricinus communis), were the first to be described. This work aimed to: 1) identifine paralogous of ricin and agglutinin, as well as the type I RIPs of castor bean; 2) analyze their phylogenetic relationships; 3) validate the use of 14 potential housekeeping genes for qRT-PCR for five developmental stages of R. communis seeds; 4) analyze the pattern of gene expression by RTqPCR of all RIPs castor identified in these same stages. A total of 18 genes that encode RIPs were identified in castor bean (Rcom RIPs), 10 of which were classified as type II and 8 as type I. The phylogenetic trees topologies suggest that Rcom RIPs were originated from multiple events of gene duplications. Two evolutionary models have been proposed for the radiation of Rcom RIPs based on gene fusion processes associated or not to events of partial duplication. The genes Act 2/7, EF β, Ubi, TIP and UBC presented the more stable expression profile and were selected for further RT- qPCR normalization experiments. The Rcom RIPI 3, 4, 5, 7 and 8 and Rcom RIPI 1, 2, 4, 5, 6 and 8 genes are actively transcribed in seeds, whereas the Rcom RIPI 1 (ricin) and Rcom RIPI 2 (agglutinin) were the most expressed. This paper presents an evolutionary model of Rcom RIPs, which can be extrapolated to other plant species. Also, corresponds to the first effort to standardize housekeeping genes for RT-qPCR in castor bean and the first that shows the expression Rcom RIPs, other than ricin and agglutinin

Caracterização filogenética das proteínas inativadoras de ribossomos (RIPs) de mamona (Ricinus communis L.) e análise da expressão dos genes Rcom RIPs durante o desenvolvimento da semente

As Proteínas Inativadoras de Ribossomos (RIPs) compreendem uma família de enzimas que inibem a síntese protéica através da depurinação de uma adenina específica do RNA ribossomal. Os membros desta família são classificados como RIPs do tipo I, quando possuem somente o RNA-N-Glicosidase e RIPs do tipo II quando além do domínio glicosidase, também apresentam um domínio de lectina. As RIPs foram mais estudadas em plantas, onde a ricina e a aglutinina, ambas RIP do tipo II de mamona (Ricinus communis), estão entre as primeiras descritas. O presente trabalho teve o objetivo de identificar parálogos da ricina e aglutinina, bem como RIPs do tipo I de mamona e analisar as suas relações filogenéticas. Além disso, validar o uso de 14 potenciais genes de referência para qRT-PCR em cinco estádios do desenvolvimento da semente de mamona. O padrão de expressão gênica por RT-qPCR de todas RIPs de mamona identificadas, também foram analisados nestes mesmos estádios. Um total de 18 genes de RIPs foi identificado em mamona (Rcom RIPs), dos quais 10 foram classificados como do tipo II e 8 do tipo I. As topologias das árvores filogenéticas sugerem que as Rcom RIPs foram originadas a partir de múltiplos eventos de duplicação gênica. Dois modelos evolutivos foram propostos para a radiação das Rcom RIPs, baseados em processos de fusão gênica associado ou não a eventos de duplicação parcial. Os genes Act 2/7, EF β, Ubi, TIP e UBC foram os que apresentaram perfil de expressão mais estável e foram selecionados para subsequente normalização dos dados de expressão das Rcom RIPs. Os genes que codificam as Rcom RIPI 3, 4, 5, 7 e 8 e as Rcom RIPII 1, 2, 4, 5, 6 e 8 são transcritos em sementes, sendo que a Rcom RIPII 1 (ricina) e a Rcom RIPII 2 (aglutinina) foram as mais expressas. O presente trabalho apresenta um modelo evolutivo das Rcom RIPs, o qual pode ser extrapolado para outras espécies de plantas. Este trabalho também demonstra o primeiro esforço para a padronização de genes de referência para RT-qPCR em mamona e o primeiro que apresenta a expressão outras Rcom RIPs, além da ricina e aglutinina.Ribosome inactivating proteins (RIPs) comprise a family of enzymes that inhibit protein synthesis, after depurination of an adenine-specific ribosomal RNA. The members of this family are classified as type I RIPs, which have a RNA-Nglycosidase domain and type II RIPs encompassing a RNA-N-glycosidase and a lectin domain.The RIPs were more studied in plants, where ricin and agglutinin, both type II RIP of castor bean (Ricinus communis), were the first to be described. This work aimed to: 1) identifine paralogous of ricin and agglutinin, as well as the type I RIPs of castor bean; 2) analyze their phylogenetic relationships; 3) validate the use of 14 potential housekeeping genes for qRT-PCR for five developmental stages of R. communis seeds; 4) analyze the pattern of gene expression by RTqPCR of all RIPs castor identified in these same stages. A total of 18 genes that encode RIPs were identified in castor bean (Rcom RIPs), 10 of which were classified as type II and 8 as type I. The phylogenetic trees topologies suggest that Rcom RIPs were originated from multiple events of gene duplications. Two evolutionary models have been proposed for the radiation of Rcom RIPs based on gene fusion processes associated or not to events of partial duplication. The genes Act 2/7, EF β, Ubi, TIP and UBC presented the more stable expression profile and were selected for further RT- qPCR normalization experiments. The Rcom RIPI 3, 4, 5, 7 and 8 and Rcom RIPI 1, 2, 4, 5, 6 and 8 genes are actively transcribed in seeds, whereas the Rcom RIPI 1 (ricin) and Rcom RIPI 2 (agglutinin) were the most expressed. This paper presents an evolutionary model of Rcom RIPs, which can be extrapolated to other plant species. Also, corresponds to the first effort to standardize housekeeping genes for RT-qPCR in castor bean and the first that shows the expression Rcom RIPs, other than ricin and agglutinin

MicroRNAs from mature and germinating soybean seeds and transfer RNA-derived fragments (TRFS) associated with argonaute proteins in arabidopsis

O advento de técnicas de sequenciamento de alta eficiência possibilitou o estudo mais aprofundado de pequenos RNAs, como os microRNAs (miRNAs), a classe melhor caracterizada, e a identificação de novas classes como a dos transfer RNA-derived Fragments (tRFs). Os pequenos RNAs podem atuar como reguladores negativos da expressão gênica do seu transcrito alvo. Este mecanismo, denominado Silenciamento Gênico Pós-Transcricional (PTGS) ou RNA interferência (RNAi), pode ocorrer pela indução da clivagem do transcrito alvo, ou pela repressão da tradução do mesmo. Em soja, ainda não foram descritos miRNAs atuantes na germinação da semente, os quais foram abordados no primeiro capítulo desta tese. Utilizando duas bibliotecas de sequenciamento de alta eficiência, uma relativa a sementes maduras e outra composta de uma combinação de sementes em germinação (3, 5 e 7 dias), foram identificados um total de 178 microRNAs, sendo 36 inéditos. Dos 178, 8 miRNAs com alvos potencialmente relacionados à germinação da semente, às rotas de auxina, giberelina, metabolismo lipídico, de nitrogênio e homeostase de potencial redox, foram validados por análise de degradoma. O segundo capítulo aborda a caracterização de tRFs em Arabidopsis associados com proteínas Argonauta (AGO), as quais são essenciais ao RNAi. Foram utilizadas 26 bibliotecas de sequenciamento de argonautas imunoprecipitadas (AGO-IP), relativas às AGOs 1, 2, 4, 5, 7 e 9, além de 3 bibliotecas de degradoma. O mapeamento destas sequências nos tRNAs de Arabidopsis revelou que estes pequenos RNAs são majoritariamente associados a AGO1 e 2, sendo a classe 5' de 19 nucleotídeos de comprimento a mais comum. Contudo, estes não obedecem aos critérios de direcionamento a proteínas AGO relativos ao primeiro nucleotídeo do pequeno RNA, como ocorre com miRNAs. Foram identificados quatro transcritos alvos, validados por análise do degradoma, os quais possivelmente sofrem PTGS via tRFs. Ambos os capítulos apresentam uma robusta caracterização in silico de pequenos RNAs em plantas inferindo suas possíveis funções. Contudo, mais experimentos devem ser efetuados para confirmação de seus papeis em soja e Arabidopsis.The advent of the deep sequencing approach enabled a better characterization of small RNAs, such as microRNAs (miRNAs), the well-known small RNA class, and the identification of new classes like the transfer RNA-derived Fragments (tRFs). The small RNAs can act as negative regulators of gene expression of their target transcript. This mechanism, known as Post Transcriptional Gene Silencing (PTGS), involves dicing of the target transcript, or translational repression. In soybean, the microRNAs acting on seed germination are unknown. These miRNAs were described in the first chapter of this thesis. Using two deep sequencing libraries, relative to the mature seeds and a combination of germinating seeds (3, 5 and 7 days). A total of 178 miRNAs were identified, including 36 new ones. Eight miRNAs had targets potentially related to seed germination including some acting on auxin and gibberellin pathways, lipid and nitrogen metabolism and redox homeostasis, and were validated by degradome analysis. The second chapter showed the characterization of Argonaut (AGO) associated tRFs in Arabidopsis. AGO is an essential protein for PTGS. A total of 26 deep sequencing libraries from immunoprecipitated Argonauts (AGO-IP), relative to the AGO 1, 2, 4, 7, and 9, plus 3 degradome libraries were used. The tRFs were mainly associated with AGO1 and 2, and the 5' class of 19 nucleotides in length was the most common one. However the tRFs did not follow the rule for AGO loading, were the first nucleotide lead the microRNA to a specific AGO. We identified four tRF target transcripts validated by degradome analysis, which possibly undergo the PTGS pathway. Both chapters present a robust in silico characterization of small RNAs in plants, inferring their possible functions. However, more experiments should be performed to confirm their roles in soybean and Arabidopsis