1,720,969 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
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
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
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
Climbing up the conserved sex determination cascade in tephritidae and mosquitoes.
No full textSex determination cascade studies in tephritidae and mosquitoes
The evolution of sex determining genes and genetic networks in flies, mosquitoes and butterflies.
No full textSex determination studies in Insect
Medfly early embryonic sexed transcriptomes: in silico approaches to identify sex-biased/male determining genes.
No full textIn 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 8-10 hours after egg laying. 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 XYXX medfly embryos at 8-10 hours from oviposition, we have defined two de novo transcriptome sets consisting respectively of 42614 (XYXX, N50=2158) and 39255 (XX, N50=2047) assembled transcripts. In this talk 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
Early sex determination steps in the mediterranean fruitfly Ceratitis capitata and its manipulation for production of a male-only progeny.
No full textIn the agricultural pest insect Ceratitis capitata, the Mediterranean fruitfly, (Medfly) the sex determination is controlled by a Y-linked male determining factor which influences, either directly or indirectly, the state of activity of the female determining master gene Cctraep (Cctra epigenetic) at 5-7 hours from oviposition. We have developed a Ceratitis transgenic sexing strain able to produce male-only progeny (95% efficiency) by transgene-mediated RNAi against the female determiner Cctraep gene. Ceratitis capitata XX pseudo-males are apparently fully fertile and hence selected XX male flies can be crossed with XX females leading to female only XX progeny. We have prepared polyA+ RNA from XX embryos and from mixed XX/XY embryos, both collected at 5.7 hours from oviposition. We have used a molecular subtractive approach to identify differential expressed genes in XY versus XX at embryonic stages. We will present the molecular strategy employed to approach this problem and preliminary data describing the identification of 8 male-biased cDNA positive clones presently under analysis. Embryonic RNAi experiments are underway to investigate the function exerted by these genes during early embryogenesis of Ceratitis
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