1,720,987 research outputs found
Sex determination in Aedes aegypti.
No full textWe proposed an hypothetical model for sex determination in Aedes that is presented here.
In this model we hypothesized the existence of two different upstream regulators that we named SR-M and SR-F (SR is for Splicing Regulator, not necessarily an SR protein).
In males a male-determining factor inhibits the SR-F protein required for the female-specific splicing of exon 5b and activates the SR-M protein required for the male-specific repression of exon 5a. It is also conceivable that the M could directly control the splicing of exon 5a. In any case, the result are the skipping of both female-specific dsx exons, with the production of a male-specific dsx isoform, and the default splicing of P1 exon, with the production of the male-specific fru isoform.
In females the absence of the M leads to the default splicing of female-specific exons 5a and to the
activation of the SR-F factor which in turn regulates the female-specific splicing of exon 5b. As a result two different female-specific DSX proteins are produced. However is still to be cleared how the repression of exon 5a is achieved in some but not all dsx female transcripts.
The activation of the SR-F factor again in turn regulates the female-specific splicing of fru P1 exon and as a result the male-specific FRU protein is not produced.
Hence we present a model with two different default splicing mode for dsx and fru gene and this is most probably the first case in the species studied till now. This could be better explained if we suppose that M factor is able to act directly on dsx gene but not on fru gene in males, due to the different binding sites we have identified (Nasonia dsxRE and dsxRE) .
In the next future we will focus our attention on identification of the upstream regulators and their functional analysis to confirm or not our speculative hypotheses
RNA-seq and Insect pests: new methods for the identification and the analysis of sex-specific genes in species of economic or sanitary interests.
No full textInsects are among the largest taxonomic animal groups on Earth. In some cases, their interactions with humans can be harmful and the knowledge of the lifecycle of insect species, e.g. disease vectors and agricultural pests, opens new chances to develop eco-sustainable control strategies, alternative to pesticides. Reproduction and sex determination are at the same time crucial aspects to understand insect biology and optimal targets to limit their population growth and diffusion. We are applying RNA-seq and digital gene expression analysis to the study of sex determination in Insect species. In particular we are comparing de novo assembled transcriptomes of early sexed embryonic populations of the agricultural pest Ceratitis capitata (Diptera, Tephritidae) to identify the unknown primary signal of sex determination in this species. We are producing de novo transcriptomes from adult males and females of the two hematophagous dipteran non-model species Aedes albopictus (Diptera, Culicidae) and Phlebotomus perniciosus (Diptera, Psychodidae), to identify genes with sex-specific or sex-biased expression, potentially involved in sex determination pathway of these vector species. We are also developing new graphical interfaces and on-line databases for comparative genomic analyses and digital gene expression analyses in biological samples with opposite sexes
A transgene-based maternally-driven RNAi system produces male-only progeny in the Mediterranean fruit fly, Ceratitis capitata.
No full textBiotech approach for SIT: a transgene-based maternally-driven RNAi system produces male-only progeny in the Mediterranean fruit fly, Ceratitis capitata
Digital differential expression analysis of early embryonic de novo assembled sexed transcriptomes of Ceratitis capitata, a world-wide agricultural pest, to identify new sex-specific and sex-biased genes.
No full textThe agricultural pest Ceratitis capitata, also known as the Mediterranean fruit fly or Medfly, belongs to the Tephritidae family, which includes a large number of damaging pest species. The knowledge of the life-cycle and of the biology of pest species opens new chances to develop eco-sustainable control strategies, alternative to pesticides. Reproduction and sex determination are at the same time crucial aspects to understand insect biology and optimal targets to limit their population growth and diffusion. In the Medfly, where XY (males) and XX (females) sexual chromosomes are present, the primary signal of sex determination, constituted by a dominant factor linked to the Y-chromosome, is still uknown. To identify this factor and to search for new early sex-biased genes we applied Illumina sequencing to RNA from 8-10 hours and 23-25 hours after egg laying (AEL) embryos of C. capitata, leading to define about 20,000 novel unique reconstructed transcripts. We utilized short reads mapping and counting, using BOWTIE and SAMTOOLS software, and the EdgeR software to evaluate and compare the expression levels of the reconstructed transcripts between sexed embryonic samples and stages. We identified about 3000 male-biased and about 1000 female-biased transcripts at 8-10h AEL. Selected candidate transcripts are under validation by qPCR expression analyses and RNAi functional analyses
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Early embryonic sexed Ceratitis capitata transcriptomes: in silico approaches to identify male biased/male determining genes.
No full textThe Mediterranean fruit fly Ceratitis capitata, or Medfly, is one of the most economically important agricultural pest insects in the world. The Medfly is a major pest affecting several key crops also in Europe, notably citrus fruits. It is a true fruit fly belongings to Tephritidae family, which contains many other important pest species.
Sex determination genes could be usefully utilized to develop biotechnological tools for insect pest control, improving or substituting the main current biological control method, the Sterile Insect Tecnique (SIT).
In C. capitata sex determination is controlled by a Y-linked male determining factor (M-factor) which influences, either directly or indirectly, the state of activity of the female determining master gene Cctraep (Cctra epigenetic) at 5-7 hours of oviposition. We have developed a Medfly transgenic sexing strain which produces male-only progeny (95% efficiency) by transgene-mediated RNAi against the female determiner Cctraep gene. C. capitata XX males are fully fertile and could be successfully mated with XX females thus leading to the production of female-only (XX) progeny. Starting from two polyA+ RNA preparations, extracted from XX-only and XX-XY Medfly embryos at 6-8 hours from oviposition, we have defined two de novo transcriptome sets consisting respectively of 36427 (XX-XY, N50=2137) and 33765 (XX, N50=1972) assembled transcripts. In this poster we will outline the assembly testing pipeline, developed with a combination of different on-line and stand alone tools, and preliminary data on the in silico subtraction approach for the identification of male-biased genes/male-determining genes
Subtractive and differential hybridization molecular analyses of Ceratitis capitata XX/XY versus XX embryos to search for male-specific early transcribed genes
No full textThe agricultural pest Ceratitis capitata, also known as the Mediterranean fruit fly or Medfly, is a fruit crop pest of very high economic relevance in different continents. The strategy to separate Ceratitis males from females (sexing) in mass rearing facilities is a useful step before the sterilization and release of male-only flies in Sterile Insect Technique control programs (SIT). The identification of genes having early embryonic male-specific expression, including Y-linked genes, such as the Maleness factor, could help to design novel and improved methods of sexing in combination with transgenesis, aiming to confer conditional female-specific lethality or female-to-male sexual reversal
Sottrazioni ai tempi della crisi: approcci molecolari ed in silico per l'isolamento del segnale primario della determinazione del sesso di Ceratitis capitata.
No full textLa mosca Ceratitis capitata (Diptera, Tephritidae) è uno dei principali parassiti agricoli su scala mondiale ed è utilizzato da svariati anni in diversi laboratori di ricerca come organismo modello per studi genetici comparati. In uno studio durato più di venti anni il nostro gruppo di ricerca ha isolato e caratterizzato gli omologhi di C. capitata dei principali geni coinvolti nel controllo della determinazione del sesso di D. melanogaster, distante filogeneticamente da C. capitata circa 130 milioni di anni.
L'interesse per tali geni è dovuto alla possibilità di studiare attraverso essi fenomeni biologici di base oltre che di sviluppare strumenti biotecnologici applicativi per il controllo di insetti parassiti. Questo studio comparato ha portato alla scoperta di una parziale conservazione del pathway di determinazione del sesso tra le due specie ed alla scoperta del ruolo epigenetico chiave del gene transformer di C. capitata (Cctra). Cctra risulta attivo soltanto in femmine (con cromosomi sessuali XX) ed è in grado di autoregolare il proprio stato di attività mediante splicing alternativo. In maschi (XY) il gene è represso, direttamente o indirettamente, nelle primissime fasi dello sviluppo embrionale (6-8 ore dalla deposizione) da un fattore legato al cromosoma Y detto “Male Determining Factor” (MDF). Ciò impedisce l'instaurarsi di una autoregolazione positiva di Cctra e porta allo sviluppo di individui di sesso maschile. Il knock-out transiente mediante RNAi del gene Cctra a stadi precoci dello sviluppo porta alla reversione sessuale di embrioni XX che si sviluppano come maschi fertili e vitali. Utilizzando tale scoperta abbiamo realizzato una linea transgenica di C. capitata in grado di produrre progenie di soli maschi (XY e revertiti XX) ed abbiamo messo a punto uno schema di incroci che ci consente di ottenere due distinte popolazioni di embrioni: misti (con cariotipo XY ed XX) e solo XX.
In questa comunicazione presentiamo gli approcci di sottrazione, molecolari ed in silico, da noi sviluppati ed in corso di utilizzazione sull'RNA estratto dalle due popolazioni embrionali per individuare geni differenzialmente espressi nei due sessi a stadi precoci di sviluppo embrionale nell'ottica di isolare tra questi il fattore determinante la mascolinità in C. capitata.
L'isolamento del segnale primario della determinazione del sesso (MDF), ad oggi non ancora caratterizzato in nessuna specie di dittero, sarebbe estremamente importante sia per scopi applicativi che per studi comparati sulla struttura, il funzionamento e l'evoluzione dei cromosomi sessuali
Sex determination in Ceratitis relies on a conserved binary genetic ON/OFF switch, splicing-based and epigenetic.
No full textThe transformer gene in the Medfly Ceratitis capitata (Cctra ep ) is the founding member of a family of conserved Serine Argi-
nine-rich (RS) splicing factor encoding genes that act as master epigenetic ON/OFF switches in sex determination in insects
as distantly related as dipterans and hymenopterans. A functional TRA protein is produced only in individuals with a female
karyotype where it is required to establish and maintain the female fate during development through a positive feedback loop
(Cctra ep ON). When zygotic activation of this loop is prevented (Cctra ep OFF), male development follows. This epigenetic self
regulatory mechanism is based on alternative splicing analogous to the one operating in Drosophila melanogaster at the level
of the gene, Sex-lethal (Sxl). In Drosophila XX individuals the splicing regulator Sxl is able to positively autoregulate (ON) and
to direct and maintain female-specific splicing of transformer (ON). TRA together with its co-regulator transformer-2 in turn
promotes female-specific splicing of the target genes doublesex and fruitless . Likewise, CcTRA and CcTRA-2 are required for
female-specific splicing of dsx and fru in Ceratitis. Both target genes contain putative tra/tra-2 binding sites (13 nt long repeats)
which were first identified in the corresponding targets of Drosophila. tra ep orthologs isolated in other insects seem to act as
binary switches that govern all aspects of sexual development. Like Cctra, the feminizing activity of these orthologs rely on a
self-regulatory function which maintains the productive female splicing mode. In Musca it was shown that maternal provision of
TRA is required to activate the female promoting tra feedback loop in the zygote. tra/tra-2 regulatory elements are present and
highly conserved in sequence and distribution in Ceratitis, Musca and all of the dipteran tra orthologs. Surprisingly, tra ortho-
logs appear to be absent in the lower dipterans Aedes aegypti and Anopheles gambiae, eventhough the tra targets dsx and fru are
present and sex-specifically expressed.
We will discuss how understanding the molecular basis of these regulatory mechanisms will help to design new genetic strategies
for pest control management of the Medfly and other insects of economical and medical relevance
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