BackgroundProviding double-stranded RNA (dsRNA) to insects has been proven to silence target genes, and this approach has emerged as a potential method to control agricultural pests by engineering plants to express insect dsRNAs. A critical step of this technology is the screening of effective target genes essential for insect development and/or survival. The tomato leafminer (Tuta absoluta Meyrick) is a major Solanum lycopersicum (tomato) pest that causes significant yield losses and has recently invaded Europe, from where it is spreading at an alarming rate. To explore RNA interference (RNAi) against T. absoluta, sequence information on potential target genes is necessary, but only a few sequences are available in public databases.ResultsWe sequenced six libraries from RNA samples from eggs, adults, and larvae at four stages, obtaining an overall total of around 245 million reads. The assembled T. absoluta transcriptome contained 93,477 contigs with an average size of 1,574 bp, 59.8 % of which presented positive Blast hits, with 19,995 (21.4 %) annotated by gene ontology. From the transcriptome, most of the core genes of the RNAi mechanism of Lepidoptera were identified indicating the potential suitability of T. absoluta for gene silencing. No contigs displayed significant similarity with a RNA-dependent RNA Polymerase. Genes from the juvenile hormone and ecdysteroid biosynthetic pathways were identified, representing potential target genes for systemic silencing. Comparisons of transcript profiles among stages revealed 1,577 genes differentially expressed at earlier larval stages, from which potential gene targets were identified. Five of these genes were evaluated using in vitro transcribed dsRNA absorbed by tomato leaflets, which were fed to 1st instar T. absoluta larvae, resulting in significant reduction of larval body weight while exhibiting significant knockdown for three of the genes.ConclusionsThe transcriptome we generated represents a valuable genomic resource for screening potential gene targets that affect the development or survival of T. absoluta larvae. Five novel genes that showed greater expression at the 1st larval stage were demonstrated to be effective potential RNAi targets by reducing larval weight and can be considered good candidates for use in RNAi-mediated crop protection.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1841-5) contains supplementary material, which is available to authorized users.

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RESUMOThe damage and the resistance levels of cultivars and accessions of common bea ns rescu ed in the Sou th a nd mou nta in regions of Espírito Santo State, Brazil, to M. incognita race 3 and M. javanica pa ra sitism were evalua ted under a greenhou se. Four rescu ed bea n genotypes (" FORT-1 0" , " FORT-1 3 ", " FORT-1 6" a nd "FORT-1 9" ) and 2 commercial cultivars: "Pérola", and "Aporé", were tested. The cu ltivar " Rico-2 3 " wa s inclu ded a s sta nda rd of su sceptibility to nematodes and non-inoculated plants constituted the control. Thus, the experiment was carried out in a completely randomized design in 3 (trea tments considering nematodes) x 7 (genotypes a nd bea n cultivars) factorial arrangement, with 7 replicates. Data were measured at 5 0 da ys after pla nt inoculation. For da ma ge qu antification, the following variables were evalu ated: plant height (PHE), number of Palavras-chave adicionais: Redução do crescimento, resistência, feijoeiro, nematóides das galhas nodes (NNO), number of trifoliate leaves (NRT), fresh matter weight (FWE) and dry matter weight (DWE) of shoots, root weight (RWE), number of root nodules (NRO) and final population (FPO) of nematodes per root system. There were no significant differences between the effects caused by M. incognita and M. javanica, but both species showed inferior values of PHE, NNO, NRT, RWE, FWE and DWE compared to controls. Concerning the levels of resista nce of bean pla nts to M. incognita, the genotypes "FORT-10", "FORT-13", "Aporé" and "FORT-16" behaved as moderately resistant, the cultivars "Rico 23" and "Pérola" low resistant, and the genotype "FORT-19" as highly susceptible. When parasitized by M. javanica, the beans "FORT-19", "Rico-23", "FORT-16" and "FORT-13" were low resistant, "Pérola" and "Aporé" susceptible and "FORT-10" highly susceptible.Avaliaram-se danos e os níveis de resistência de cultivares e acessos de feijoeiro-comum resgatados nas regiões Sul e Serrana do Estado do Espírito Santo ao parasitismo de M. incognita raça 3 e M. javanica em casa de vegetação. Foram testados quatro genótipos resgatados de feijoeiro ("FORT-10", "FORT-13", "FORT-16" e "FORT-19"), e mais 2 cultivares comerciais: "Pérola" ; e "Aporé". O cultivar "Rico-23" foi incluído como padrão de suscetibilidade aos nematóides e plantas nã o inocu la da s constitu íra m a testemu nha . Desta forma , o experimento foi conduzido em delineamento inteiramente casualizado em esquema fatorial 3 (tratamentos considera ndo nematóides) x 7 (genótipos e cultiva res de feijoeiros), com 7 repetições. Os dados foram mensurados aos 50 dias após a inoculação das plantas. Para a qu antificação de danos foram avaliadas: altura das pla nta s (ALT ), número de nós (NOS), número de folhas trifolioladas (NFT), peso da Santos, L.N.S.; Alves, F.R.; Belan, L.L.; Cabral, P.D.S.; Matta, F.P.; Jesus Junior, W.C.; Moraes, W.B.Quantificação de danos e reção de genótipos de feijoeiro (Phaseolus vulgaris L.) à Meloidogyne incognita raça 3 e M. javanica. Summa Phytopathologica, v.38, n.1, p.24-29, ...

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