Transgene Silencing and Transgene-Derived siRNA Production in Tobacco Plants Homozygous for an Introduced AtMYB90 Construct

Transgenic tobacco (Nicotiana tabacum) lines were engineered to ectopically over-express AtMYB90 (PAP2), an R2–R3 Myb gene associated with regulation of anthocyanin production in Arabidopsis thaliana. Independently transformed transgenic lines, Myb27 and Myb237, accumulated large quantities of anthocyanin, generating a dark purple phenotype in nearly all tissues. After self-fertilization, some progeny of the Myb27 line displayed an unexpected pigmentation pattern, with most leaves displaying large sectors of dramatically reduced anthocyanin production. The green-sectored 27Hmo plants were all found to be homozygous for the transgene and, despite a doubled transgene dosage, to have reduced levels of AtMYB90 mRNA. The observed reduction in anthocyanin pigmentation and AtMYB90 mRNA was phenotypically identical to the patterns seen in leaves systemically silenced for the AtMYB90 transgene, and was associated with the presence of AtMYB90-derived siRNA homologous to both strands of a portion of the AtMYB90 transcribed region. Activation of transgene silencing in the Myb27 line was triggered when the 35S::AtMYB90 transgene dosage was doubled, in both Myb27 homozygotes, and in plants containing one copy of each of the independently segregating Myb27 and Myb237 transgene loci. Mapping of sequenced siRNA molecules to the Myb27 TDNA (including flanking tobacco sequences) indicated that the 3′ half of the AtMYB90 transcript is the primary target for siRNA associated silencing in both homozygous Myb27 plants and in systemically silenced tissues. The transgene within the Myb27 line was found to consist of a single, fully intact, copy of the AtMYB90 construct. Silencing appears to initiate in response to elevated levels of transgene mRNA (or an aberrant product thereof) present within a subset of leaf cells, followed by spread of the resulting small RNA to adjacent leaf tissues and subsequent amplification of siRNA production

Parental transposable element loads influence their dynamics in young Nicotiana hybrids and allotetraploids.

This is the peer reviewed version of the following article: Mhiri, C., et al. (2018). "Parental transposable element loads influence their dynamics in young Nicotiana hybrids and allotetraploids." New Phytologist 0(0)., which has been published in final form at https://doi.org/10.1111/nph.15484. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsThe genomic shock hypothesis suggests that allopolyploidy is associated with genome changes driven by transposable elements, as a response to imbalances between parental insertion loads. To explore this hypothesis, we compared three allotetraploids, Nicotiana arentsii, N. rustica and N. tabacum, which arose over comparable time frames from hybridisation between increasingly divergent diploid species. We used sequence-specific amplification polymorphism (SSAP) to compare the dynamics of six transposable elements in these allopolyploids, their diploid progenitors and in corresponding synthetic hybrids. We show that element-specific dynamics in young Nicotiana allopolyploids reflect their dynamics in diploid progenitors. Transposable element mobilisation is not concomitant with immediate genome merger, but occurs within the first generations of allopolyploid formation. In natural allopolyploids, such mobilisations correlate with imbalances in the repeat profile of the parental species, which increases with their genetic divergence. Other restructuring leading to locus loss is immediate, nonrandom and targeted at specific subgenomes, independently of cross orientation. The correlation between transposable element mobilisation in allopolyploids and quantitative imbalances in parental transposable element loads supports the genome shock hypothesis proposed by McClintock.. The work was funded by the Association pour laRecherche sur les Nicotiane ́es (ARN; BTH01453 researchcontract), by the Agence Nationale de la Recherche (ANR-05-BDIV-015), by Campus France (PHC Barrande 09150SH,PHC Alliance 08782YM), by the Czech Science FoundationGA CR (501/12/G090 grant) and by Natural EnvironmentResearch Council. The IJPB benefits from the Agence Nationalede la Recherche through the Labex Saclay Plant Science-SPSproject (ANR-10-LABX-0040-SPS

Bronquiectasias : tratamento cirúrgico : análise de 437 casos

-Introdução: Este trabalho apresenta a experiência cirúrgica em 437 pacientes submetidos à ressecção pulmonar para tratamento de bronquiectasias, avaliando evolução pós-operatória e o impacto quanto à melhora dos sintomas. -Métodos: Foram analisados retrospectivamente os prontuários médicos de 437 pacientes submetidos à ressecção pulmonar para tratamento de bronquiectasias em uma única instituição, entre Janeiro de 1978 e Dezembro de 2010. Os pacientes tinham 16 ou mais anos de idade, e as bronquiectasias foram diagnosticadas pelas manifestações clínicas e por tomografia computadorizada do tórax. Pacientes portadores de fibrose cística e os submetidos a transplante pulmonar foram excluídos. -Resultados: A amostra incluiu 437 pacientes (249 do sexo feminino; 188 do masculino). A idade média dos pacientes na época da cirurgia era de 38,45 anos (variando de 16 a 80 anos). O sintoma mais comum na apresentação era tosse produtiva (79,4%). A causa identificada como mais comum das bronquiectasias foi infecção respiratória na infância (49,2%). Cirurgia unilateral foi realizada em 415 pacientes (95,0%), e em 344 toda a área com bronquiectasias foi ressecada. Dentre os procedimentos cirúrgicos utilizados, o principal foi lobectomia média em 147 pacientes (33,6%) e segmentectomia (32,3%). Após a cirurgia, 94,4% de 267 pacientes questionados referiram melhora de seus sintomas, 68,9% deles considerando-se assintomáticos. Ocorreu 1 (um) óbito no pós operatório. -Conclusões: O tratamento cirúrgico das bronquiectasias mostrou-se altamente eficiente, em termos de melhora dos sintomas dos indivíduos acometidos, sendo realizado com taxas de morbidade aceitáveis, mortalidade praticamente nula, e com excelentes resultados em termos de melhora dos sintomas.Background. This work presents the surgical experience of 437 patients undergoing to lung resection for the treatment of bronchiectasis, evaluating both the impact on postoperative clinical improvement and complications of the surgical procedure. Methods It was retrospectively analyzed the medical charts of 437 consecutive patients who underwent a surgical lung resection for treatment of bronchiectasis in a single institution, between January 1978 and December 2010. Patients were 16 years or older and bronchiectasis was diagnosed by symptoms and computed tomography. Patients with cystic fibrosis and bronchiectasis the ones that underwent to lung transplantation were excluded. Results The study sample included 437 patients (249 females; 188 males). Mean age at time of surgery was 38.45 years old (range: 16 to 80). The most common presenting symptoms were cough (79.4%). The most common etiology of bronchiectais was childhood infections (49.2%). Unilateral approach was performed in 415 (95.0%) and in 344 the total bronchiectasic site were resected. Several surgical procedures were used, the majority was medium lobectomy in 147 (33.6%) and segmentectomy (32.3%). After surgery, 94.4% of the patients improved their symptoms, 68,9% following practically assymptomatic. One postoperative death occurred. Conclusions Bronchiectasis may be treated by surgical management, particularly in developing countries where it is very prevalent. It can be performed with acceptable morbidity rates, practically without mortality, and with excelent results in terms of symptoms improvement