Schizophrenia is a complex disorder affecting 1% of the population and is highly heritable, but the majority of contributing genetic factors has remained elusive. Current risk estimates for clinical practice are primarily determined by family history and associated empirical risk. Copy number variants (CNVs) may hold the key to explaining the missing heritability in schizophrenia research; schizophrenia risk estimates as high as 30% have been found for the most-studied CNV associated with schizophrenia, 22q11. Currently, there are methods to identify CNVs though previously collected data from SNP microarrays that would facilitate these types of studies. To determine if algorithms that call CNVs from microarray data are robust four genomic regions with putative CNVs called by the Wellcome Trust Consortium using Birdseye in Birdsuite with Affymetrix 6.0 array raw SNP intensities, primarily affecting genes CHD1L, COX5B, PAK7, ZFYVE20, were validated using Taqman real-time qPCR assays in 29 samples by research groups at VCU and Dublin. CNVs called from the algorithm were 100% validated at VCU though there were false negatives from the algorithm that were validated. Two samples at loci with putative duplications were not called by the Dublin group, which may be because of differing sensitivities of the Taqman assays to be able to detect a 50% difference in copy number between duplications and diploid controls, or because of another technical or analytical difference between the two sites. Deletion frequency of one common CNV found in the gene ERBB4, was assessed by qPCR in both Irish singleton (ICCSS) and Irish family (IHDSF) samples and compared with Irish control (Trinity Biobank) and North American control populations. The ERBB4 deletion frequency was not significantly different when comparing the Irish controls to the Irish singleton or the Irish family samples though the family samples were different when compared against the North American control population, which suggests population stratification, rather than a true association between ERBB4 and increased schizophrenia risk. Current clinical practice has been improved by knowledge and evaluation of CNV-related disorders that include risk for psychosis and additional phenotypes. Genotyping of individuals with known psychosis has led to improved patient care for non-psychosis-related phenotypes associated with CNVs. Individuals with suspected genomic disorders that are found to have CNVs can be counseled on potential psychosis risk and potential risk to their offspring. Recurrent CNVs may hold promise in future clinical practice in order to individualize risk estimates in the general patient population, and increase the number of individuals able to receive anticipatory treatment to minimize disease severity.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

High-value industrial oils are essential for many processes and have great economic and environmental impacts. The tung tree produces a high-value seed oil. Approximately 80% of tung oil is α-eleostearic acid, which has a high degree of unsaturation thus giving it properties as a drying oil. The identification of the biological components in tung is imperative to further the knowledge of its processes. Four unique tung acyl-CoA binding proteins, VfACBP3a, VfACBP3b, VfACBP4, and VfACBP6 were identified and the genes encoding them were cloned and analyzed to determine their biological roles. The VfACBPs were observed to be similar to other organisms' ACBPs, especially Arabidopsis thaliana. In addition, each gene was expressed in all tung tissues. They were shown to interact with VfDGAT1 and VfDGAT2, two known components of tung lipid metabolism. Finally, VfACBP3a and VfACBP6 were expressed in the seeds of transgenic plants to study the effects of VfACBP expression on seed lipid fatty acid content.

L'utilisation de molécules stimulatrices de défense des plantes (SDP), également appelées inducteurs de résistance, constitute une alternative possible aux traitements fongicides conventionnels pour contrôler les maladies dues aux chanpignons phytopathogènes. Dans cette étude, nous avons mis en évidence que trois produits à caractère SDP (FSOV2, FSOV7 et FSOV10) protègent le blé (Triticum aestivum L.) contre la septoriose (Mycosphaerella graminicola, anamorphe Zymoseptoria tritici) lorsqu'ils sont utilisés de façon préventive, mais cette protection dépend fortement du cultivar considéré. Les cultivars Alixan, Premio et Altigo testés ici présentaient au départ des niveaux de résistance distincts à la septoriose. Les protections obtenues ne sont pas liées à un effet direct sur la germination des spores du champignon, mais à l'induction des mécanismes de défense chez le blé qui réduisent la nécrose foliaire et la sporulation du champignon. Ainsi, l'observation des différents stades du processus infectieux de M. graminicola en microscopie et le dosage des activités enzymatiques fongiques de dégradation des parois (CWDE) in planta révèlent que le niveau de protection induite varie avec le SDP appliqué et avec le cultivar traité. L'expression de neuf gènes impliqués dans différentes voies de défense, suivi par RTqPCR, et les activités enzymatiques peroxydase et phénylalanine ammonia lyase ont été mesurée au cours du temps, depuis le traitement par les SDP jusqu'à 5 jours après infection. Les résultats obtenus montrent, que les mécanismes de défense sont induits différemment en fonction du cultivar et en fonction du SDP appliqué. Ces résultats suggèrent que la réussite au champ des SDP est conditionnée de façon déterminante par le choix du couple SDP-cultivar. / The use of resistance inducers (RI) is a potential alternative to conventional fungicide treatments against plant fungal diseases. In the present study, we revealed that preventive applications of three RI conferred protection efficacies against M. graminicola, with protection levels varying with the wheat cultivar. Alixan, Premio and Altigo cultivars were previously known to exhibit distinct resistance levels to M. graminicola. The observed protections did not result from a direct effect on spore germination, but were related to the induction of wheat defense mechanisms. The induced resistances reduced foliar necrosis, as well as the sporulation level of the fungus. Microscopic observations of the infection process of M. graminicola and cell wall degrading enzymes (CWDE) activities measured in planta showed that the applied RI as well as the considered treated wheat cultivar influences the impact on the infection process and the protection efficacy. We investigated from the time of treatment until 5 days after inoculation plant peroxidase and phenylalanine ammonia lyase activities and the expression of nine genes involved in distinct defense pathways. Our results indicated that defense mechanisms are differently induced according both to the wheat cultivar and the RI. Therefore, the successful use of RI at the field level strongly depends on the RI-cultivar combination.

Os sistemas de cultivo agrícola são essenciais à sociedade. A questão atual é saber como mantê-los produtivos sem afetar drasticamente os diferentes ecossistemas e ciclos biogeoquímicos. Sabe-se que a atividade biológica dos solos é de crucial importância à saúde dos mesmos e à produtividade. Deste modo, a implantação de técnicas ambientalmente corretas com monitoramentos eficientes, baseados na qualidade do solo, é fundamental para valorizar a sua conservação. Esta tem sido o foco de pesquisas nas últimas décadas, sendo que refletem ação antrópica, principalmente pela emissão dos gases do efeito estufa (GEEs). O uso de sistemas conservacionistas destaca-se pela viabilidade econômica e ambientalmente benéfica em relação ao manejo convencional. O sistema integração lavoura-pecuária tem sido utilizado para minimizar os impactos ambientais da exploração agrícola, a fim de preservar as características físicas, químicas e biológicas do solo, estendendo sua resiliência e aumentando a produtividade. Os microrganismos são responsáveis por diversos processos biológicos essenciais ao ambiente e algumas espécies participam produzindo ou oxidando o metano (CH4), um dos gases do efeito estufa. Estes são influenciados principalmente pelas mudanças de uso do solo, que quando relacionadas ao manejo inadequado podem alterar a qualidade do solo, a produtividade e a emissão de gases. Assim, a avaliação dos solos dos sistemas agrícolas, sob a interação rizosférica de diferentes culturas e a criação de um ambiente anóxico se faz necessário para entender o comportamento de tais comunidades. Os sistemas de integração lavoura-pecuária e a rotação de culturas foram investigados em relação a microbiota funcional do solo, em função de fatores como ao histórico da área e umidade. Foram avaliadas a abundância, por PCR em tempo real, e a estrutura das comunidades Archaea e Bacteria por TRFLP, e a potencialidade de atuação do solo como emissor e mitigador de CH4 através da quantificação dos microrganismos metanogênicos e metanotróficos de áreas agrícolas e reflorestamento do Alto Xingu, no município de Querência. Com elas foi possível observar que os microrganismos são estruturados, primariamente, em função do tipo de solo e consecutivo efeito rizosférico dos vegetais, de forma que os sistemas de integração lavoura-pecuária (ILP) apresentaram sutilmente maior estabilidade em relação ao sistema rotacionado de soja/milheto, devido ao sistema radicular da pastagem fornecer maior proteção e liberação de exsudatos. Pelas semelhanças existentes com os sistemas ILP, a área de reflorestamento se encontra em recuperação transitória, em uma média da similaridade entre as enzimas de restrição HhaI e MspI, de 85%; e 65% em relação à floresta, que se estruturou de maneira diferenciada das demais áreas. Outro fator de diferenciação das áreas agrícolas foi a forte influência da calagem o que eleva o pH e concomitantemente apresentou teores elevados de Ca e Mg. Já as comunidades de metanotróficas não apresentaram variação em função das metanogênicas, em que a saturação hídrica promoveu seu crescimento somente nos solos de floresta, onde ocorre maior incorporação de matéria orgânica / Agricultural faming systems are essential to society. The current question is how to keep them productive without drastically affecting different ecosystems and biogeochemical cycles. It is known that the soil biological activity is crucial to the health and productivity. Thus, the implementation of environmentally correct techniques with efficient monitoring, based on soil quality is critical to enhance their conservation. This has been the focus of research in recent decades, and reflects human action, mainly by the emission of greenhouse gases (GHGs). The use of conservation tillage systems distinguished by economic viability and environmentally beneficial compared to conventional tillage systems. The crop-livestock system has been used to minimize the environmental impacts of farming, in order to preserve the physical, chemical and biological soil properties, extending its resilience and increasing productivity. Microorganisms are responsible for many essential biological processes to the environment and some species participate in production or oxidation of methane (CH4), a greenhouse gas. These are mainly influenced by land use changes, that when related to inadequate management may alter soil quality, productivity and gases emissions. Thus, the evaluation of soils for agricultural systems under the rhizospheric interaction of different cultures and creating an anoxic environment is needed to understand the behavior of such communities. Crop-livestock systems and crop rotation were investigated in relation to functional soil microbiota, depending on factors such as the area history and moisture. Genes abundance were assessed by real-time PCR, while Archaea and Bacteria community structure by TRFLP, and the potential role of soil as releaser and mitigator of CH4 through the quantification of methanogens and methanotrophs in agricultural areas and reforestation of the Upper Xingu, at Querência city. Through the techniques of qPCR and TRFLP was observed that microorganisms are structured primarily on the type of soil, followed by rhizosphere effect of plants. In this way, crop-livestock integration systems (CLI) are subtly stable then rotational system of soybean/millet due to pasture root system to provide greater protection and root exudation. Alike CLI systems, the reforestation area is in transient recovery on average between the restriction enzymes HhaI and MspI, 85%; and 65% in relation to forest, this structures itself in a differentiated manner from the other areas. The farming areas present strong influence of liming, which leads to grow pH and concomitantly high Ca and Mg contents. The methanotrophic community did not vary due to the methanogenic community, and the water saturation promotes the growth of methanogenic communities only in forest soils where occurs greater organic matter incorporation

O gênero Methylobacterium é composto por bactérias de coloração rósea, metilotróficas e que podem colonizar endofiticamente a planta. Algumas espécies deste gênero são capazes de promover o crescimento vegetal e reduzir o ataque de fitopatógenos. A linhagem de M. mesophilicum SR1.6/6 foi isolada de ramos de citros e devido a sua interação com a planta hospedeira e com patógenos associados a planta, tem sido foco vários trabalhos. Os sistemas de secreção e as bombas de efluxo podem estar envolvidos na modulação das interações de bactérias endofíticas com seus ambientes. Assim, neste estudo foi analisada a composição dos exsudatos produzidos pelas plantas de milho e citros na interação com a SR1.6/6 por GC-MS, foi realizada a reanotação de genes relacionados ao sistema de secreção e bombas de efluxo e foi avaliada a expressão de alguns genes destes sistemas na interação com Zea mays e Citrus sinensis por qPCR. Foram encontrados sistemas de secreção tipo I, II e V, vias SEC e TAT e bombas de efluxo, principalmente super-expressos durante a interação com a planta hospedeira. / Methylobacterium genus is composed by pink-pigmented facultative methylotrophic bacteria. Some species of this genus are able to promote plant growth and reduce the incidence of pathogens. The SR1.6/6 strain of Methylobacterium mesophilicum is a bacterium isolated from citrus and due to its interaction with the plant has been the focus of several studies. Multidrug efflux pumps and secretion system can be involved modulating the interactions of bacteria with their environments. In this work was analised the root exsudates composition from two host plants citrus and corn interacting with SR1.6/6 by GC-MS technique, additionally was searched and reannotated genes related to secretion system and some multidrug efflux pumps and finally evaluated the gene expression of some of this genes during the interaction with Zea mays and Citrus sinensis by qPCR. Type I, II and V secretion system, SEC and TAT pathway and some multidrug efllux pumps were found in this strain according gene expression. This systems were up-regulated mainly during interaction with host plant.

Genes homeobox, vitais para muitos aspectos relacionados com crescimento e diferenciação celular, têm sido descritos desregulados em alguns cânceres. Seu papel na carcinogênese, principalmente de carcinomas epidermóides de boca, permanence pouco claro e pobremente caracterizado. Desse modo, esse estudo objetivou avaliar, em cultura de células, o perfil de expressão de seis genes homeobox (ASH2L, HOXA7, HHEX, PKNOX1, PITX1, TGIF) selecionados dentre aqueles previamente identificados no Projeto Genoma Câncer de Cabeça e Pescoço (2001) sob estímulo de EGF e TGF-beta1. Para tal, linhagens celulares de carcinoma epidermóide de cabeça e pescoço primário (HN6) e metastático (HN31) e uma linhagem não-tumoral (HaCat) foram cultivadas sob condições-padrão. Após a confecção dos cDNAs de cada linhagem, por meio de RT-PCR, os transcritos foram amplificados e quantificados pela técnica de PCR em tempo real. Os dados foram normalizados com o gene HPRT e a quantificação relativa foi realizada seguindo o método do delta Ct. De acordo com os resultados foi possível verificar que o EGF produziu uma modulação variável da expressão dos genes avaliados em todas as linhagens celulares, enquanto que, em geral, o TGF-beta1 foi capaz de aumentar significantemente (ANOVA, p<0,05) a expressão dos transcritos de 5 genes homeobox (HOXA7, HHEX, PKNOX1, PITX1, TGIF). Particularmente transcritos dos genes PITX1 e TGIF foram signicantemente mais expressos nas linhagens tumorais (HN6 e HN31) frente à linhagem não-tumoral quando tratados com TGF-beta1. Desse modo, sugere-se que os genes homeobox estudados desempenhem diferentes funções na carcinoma epidermóide de boca, e que, especialmente PITX1 e TGIF atuem como oncogenes inibindo a resposta anti-proliferativa dependente de TGF-beta e levando a progressão tumoral. / Homeobox genes, vital to many aspects related with cellular growth and differentiation, had been described as deregulated in some cancers. Their role in carcinogenesis, mainly oral squamous cell carcinomas, remains unclear and poorly characterized. Thus, this study had the purpose to evaluate, in cell cultures, the expression profile of six homeobox genes (ASH2L, HOXA7, HHEX, PKNOX1, PITX1, TGIF) selected among genes previously identified in the Head and Neck Cancer Genoma Project (2001), under stimulation with EGF and TGF-beta1. Oral squamous cell carcinoma cell lines from primary tumour (HN6) and from methastasis (HN31), and a non-tumoral cell line (HaCat) were cultured under standard procedures. CDNAs were obtained by RT-PCR and the transcripts were amplified and quantified by real-time PCR. Data were normalized by HPRT gene and the relative quantification was made by the delta Ct method. According to the results, it was possible to observe that EGF produced a variable modulation of the analyzed genes, in all cell lines. Generally, TGF-beta1 was able to significantly increase (ANOVA, p<0,05) the expression of the transcripts of 5 homeobox genes (HOXA7, HHEX, PKNOX1, PITX1, TGIF). Transcripts of PITX1 and TGIF genes were particularly more expressed in the tumoral cell lines (HN6 e HN31), when compared to the non-tumoral cell line, when treated with TGF-beta1. It is suggested that the studied homeobox genes play different roles in oral squamous cell carcinoma and that, especially the PITX1 and TGIF act as oncogenes, inhibitting the TGF-dependent anti-proliferative response, leading to tumour progression.

Legionella pneumophila, the causative agent of Legionnaires' disease, is a water born pathogenic bacteria commonly found in natural and manmade water systems such as rivers, lakes, wet soil, hot and cold water storage systems (being able to survive at temperatures between 6-63 °C, and proliferating between 20-45 °C), showerheads, cooling towers and spa pools. The main pathway of exposure to Legionella is by inhaling the aerosols containing the microorganism. Legionnaires' disease can be fatal if not diagnosed and treated at the right time. Practical Legionella control starts with a risk assessment of the water system and followed by the regular monitoring and water sampling. UK Health and Safety Executive (HSE) have implemented strict legislations to protect the public from Legionnaires' disease. This research highlights and addresses three major data gaps identified in Legionella control and management strategy employed in the UK and worldwide; namely, (i) the underestimation of microbiological threat in current cold water storage sampling strategy, (ii) the inability of current qPCR diagnostic methods to detect live Legionella in water samples, and (iii) the lack of predictive 'risk management system' for Legionella control in domestic water systems. During my PhD, 15 relevant cold water storage tanks (selected from more than 6000 tanks surveyed at different sites located in different London Boroughs) were used to investigate the risk factors that contribute towards Legionella proliferation, and revealed serious shortcomings in the appropriateness of the water sample taken for regulatory testing. Secondly, molecular biology research was carried out to develop an accurate, reliable and rapid testing method for the detection and quantification of live Legionella using qPCR techniques. This was successfully achieved by extracting RNA from a Legionella lenticule, converting the RNA into cDNA and amplifying the cDNA using qPCR techniques. Finally, regular monitoring data from 120 London buildings (60 known to be Legionella positive and 60 known to be Legionella negative) was used to identify the possible risk factors contributing towards Legionella outbreaks. Data for these factors was then used to develop a predictive risk model for Legionella contamination using Principal Component Analysis (PCA). The model was validated with 66 new London buildings and 9 out of London buildings. The model showed 100% accuracy in predicting the risk of Legionella by distinguishing infected and non-infected sites in London as well as for the sites in out of London.

Accurate smoltification and disease management in Atlantic salmon (Salmo salar) are key issues for the aquaculture industry. Due to their anadromous lifecycle the transfer of salmon from fresh water (FW) to seawater (SW) is crucial to their survival; too early can cause mortality, too late can cause desmoltification and long-term health problems. Both scenarios can increase susceptibility to four viral diseases: Salmon alphavirus (SAV), Infectious salmon anemia virus (ISAV), orthoreovirus (PRV), and Piscine myocarditis virus (PMCV). They all show similar clinical and histopathological symptoms and can easily spread throughout farms. Understanding the initial innate immune response to these viruses may provide biomarkers that could help identify and monitor infections. An in house and onsite Na+/K+ ATPase (NKA) qRT-PCR assay was developed for the salmon biomarker ATPase to test smoltification readiness in salmon smolts. Tested against NKA enzymatic assays it showed a similar success rate over 3 years: NKA qRT-PCR (57%), NKA activity assay (60%). Onsite tests confirmed that the ATPase mRNA transcript is a useful biomarker for smoltification detection. An in-lab and mobile multiplex qRT-PCR assay was developed for detection of SAV, PRV and PMCV. The analytical sensitivity of the SAV (86.5% SE 0.11), PRV (90.94%, SE 0.09) and PMCV (100.46%, SE 0.19) assays was 102 copies for PMCV and 103 for SAV and PRV. Initial results suggest individual assays could be run on site at farms. Addition of an internal control, probit analysis and viral positive tests are still required for multiplex assay integration. Salmon erythrocytes were infected with ISAV, SAV and Poly I:C to investigate whether they induce and up-regulate innate immune response genes. All genes were expressed at low levels in all parameters investigated including non-infected control erythrocytes. These findings suggest erythrocytes act as an initial buffer to viral infections and may help stimulate the innate immune response.

O trigo (Triticum aestivum L.) é uma importante cultura no Brasil. Poucas cultivares são recomendadas para produção do tipo sequeiro no Bioma Cerrado onde a escassez de água limita o rendimento de grãos. Aqui reportamos uma análise de transcriptoma do MGS1 Aliança (cultivar de trigo adaptada ao Cerrado) sob estresse de seca. Um grupo de 4.422 transcritos diferencialmente expressos foi encontrado em raízes e folhas. O número de transcritos reprimidos em raiz (1.102) foi menor que os transcritos induzidos (1.706), enquanto o oposto ocorreu em folhas (1,017 induzidos e 647 reprimidos). O número de transcritos comuns entre ambos órgaõs foi 1.249, enquanto 2.124 foram específicos para raíz e 1.049 específicos para folhas. Análises de RT-qPCR de 35 transcritos selecionados ao acaso revelou uma correlação de 0,78 com os dados de transcriptoma. Os transcritos diferencialmente expressos foram distribuídos por todos os cromossomos e componentes do genoma. O número de transcritos no genoma B foi maior do que nos genomas A e D. Ainda, um grande número de transcritos relacionados à seca foi mapeado nos cromossomos 3B, 5B e 2B. Quando consideramos ambos órgãos, 116 diferentes rotas metabólicas foram alteradas. Uma rota em comum, entre as três mais alteradas em ambos órgãos, foi o metabolismo do amido e da sacarose. A comparação de transcritos derivados de raiz e de folha permite a identificação de transcritos importantes relacionados à respota ao estresse de seca em cada um destes órgãos. Os dados obtidos, também, abrem caminho para o desenvolvimento de futuros marcadores e seleção de genes candidatos ligados à característica. Estes resultados são úteis para o entendimento de rotas metabólicas envolvidas na tolerância à seca em trigo. A informação gerada será usada, a mais longo prazo, para propósitos de transgenia. Para isto, a metodologia de duplo-haploides é desejável e uma primeira investigação sobre a eficiência de protocolo se mostrou necessária. Micrósporos são células gaméticas com capacidade de dar origem a uma nova planta via embriogênese in vitro. Plantas duplo-haploides geradas pela cultura de micrósporos isolados são completamente homozigotas e representam uma importante ferramenta para estudos genéticos e melhoramento de plantas O processo androgenético é desencadeado por diferentes pré-tratamentos de estresse, os quais são empregados para mudar os micrósporos da rota gametofítica para a rota esporofítica. Embora a cultura de micrósporos isolados tenha inúmeras vantagens, importantes limitações tem impedido sua apliação em larga escala. Diferenças genotípicas na resposta androgenética e na formação de plantas albinas ainda constituem desafios. Embora o albinismo seja principalmente uma característica genética, pré-tratamentos e meios de cultura apropriados podem evitar este fenômeno até certo ponto. A resposta androgenética de cinco genótipos de trigo brasileiro foi avaliada no presente estudo. Dois pré-tratamentos foram testados: frio (4°C) e ácido 2-hidroxinicotinico (100 mg/L). O frio foi melhor que o pré-tratamento químico, produzindo mais plantas verdes em quatro de cinco genótipos. Somente dois genótipos brasileiros tratados com ácido 2-hidroxinicotinico produziram plantas, e um deles apenas uma única planta albina. Nossos reultados mostram, também, que o meio semilíquido (contendo 10% de Ficoll) promoveu uma maior resposta androgenética que o meio líquido, aumentando o número de embriões e plantas regeneradas. / Wheat (Triticum aestivum L.) is an important crop cultivated in Brazil. Few cultivars are recommended for rainfed production in the Cerrado Biome where water scarcity limits grain yield. Here we report a transcriptome analysis of MGS1 Aliança (a wheat cultivar adapted to the Cerrado) under drought stress. A set of 4,422 differentially expressed transcripts was found in roots and leaves. The number of down-regulated transcripts in roots (1,102) was lower than the up-regulated transcripts (1,706), while the opposite occurred in leaves (1,017 induced and 647 repressed). The number of common transcripts between the two tissues was 1,249, while 2,124 were specific to roots and 1,049 specific to leaves. Quantitative RT-PCR analysis of 35 randomly selected transcripts revealed a 0.78 correlation with the transcriptome data. The differentially expressed transcripts were distributed across all chromosomes and component genomes. The number of transcripts on the B genome was greater than on the A and D genomes. Additionally, a greater number of drought related transcripts was mapped on chromosomes 3B, 5B and 5D. When considering both tissues, 116 different metabolic pathways were changed. One common pathway, among the top three changed pathways in both tissues, was starch and sucrose metabolism. The comparison of root- and leaf-derived transcripts allows the identification of important transcripts related to water stress response in each of these tissues. It also paves the way for future marker development and selection of candidate genes linked to that trait. These results are useful for understanding the metabolic pathways involved in wheat drought response. The information generated will be used for transgenic wheat purposes. For this the doubled-haploid method is desirable and an investigation about the protocol eficiency is needed. Microspores are gametic cells with capacity to give rise to a new plant via in vitro embryogenesis. Doubled haploid plants generated by isolated microspore culture are completely homozygous and represent an important tool for plant genetics and breeding research. This process is triggered by different stress pretreatments, which are employed to switch microspores from gametophytic to a sporophytic pathway. Although isolated microspore culture has innumerous advantages, important limitations have prevented its application on a large scale. Genotypic differences in androgenic response and the formation of albino plants remain great challenges. Although albinism is a major genetic characteristic, appropriated pretreatments and culture medium can avoid this phenomenon to some extent. The androgenic response of five Brazilian wheat genotypes was evaluated in the present study. Two pretreatments were tested: cold (4°C) and 2-hydroxynicotinic acid (100 mg/L). Cold was better than chemical pretreatment, producing more green plants in four out of five genotypes. Only two Brazilian genotypes treated with 2-hydroxynicotinic acid produced plants, and one of them produced a single albino plant. Our results also show that semi-liquid medium (containing 10% Ficoll) promoted a higher androgenic response than did liquid medium, increasing the number of embryos and regenerated plants.