Ciências Biológicas e da Saúde
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/3
Navegar
59 resultados
Resultados da Pesquisa
Item Sequenciamento, caracterização e comparação evolutiva dos plastomas de Euterpe edulis e Euterpe Oleracea(Universidade Federal de Viçosa, 2017-07-25) Silva, Odyone Nascimento da; Rogalski, Marcelo; http://lattes.cnpq.br/3969533047091830As espécies E. edulis e E. oleracea pertencem à família Arecaceae e são as espécies mais importantes desse gênero, pela multiplicidade de usos e com destaque para comercialização de seus frutos e palmito. Neste sentido, reportamos a sequência completa e caracterização do genoma plastidial de ambas as espécies, que são as primeiras da tribo Euterpeae a terem seu plastoma sequenciado. Os plastomas das duas espécies apresentam uma estrutura quadripartida circular, que é típica na maioria das angiospermas. A estrutura do plastoma, a ordem dos genes e o conteúdo gênico são semelhantes às outras espécies da família Arecaceae. Exceções foram observadas nos genes ycfl e o rpsló que aparecem como pseudogenes em algumas espécies da família Arecaceae e nesta pesquisa aparecem na forma funcional em ambas as espécies. A análise de divergência de genes mostra que o gene ycfl é um dos genes mais divergentes na família Arecaceae. As espécies do gênero Euterpe mostraram uma alta conservação de sítios de edição de mRNA e a presença de 23 predições de sítios mRNA não observados em outras palmeiras. As duas espécies apresentam distribuição similar de SSRs com algumas regiões contendo um número mais elevado dos localizados principalmente nas regiões de cópia única. Nos plastomas das duas espécies foram localizados e caracterizados seis hotspots de divergência de nucleotídeos entre as espécies em estudo, todos localizados na região de cópia única. Baseadas no plastoma de 36 espécies pertencentes à família Arecaceae, as árvores filogenômicas obtidas por duas análises estatísticas mostraram um alto valor de suporte para as relações entre as tribos amostradas, incluindo o gênero Euterpe dentro da tribo Euterpeae. Por tanto, o sequenciamento permitiu caracterizar o genoma plastidial, identificar sequências repetidas e microssatélites, detectar pontos de divergência gênica, analisar divergência dos genes e previsão de edição de mRNA nas duas espécies do gênero Euterpe, que serão úteis para seleção de dados em futuros estudos filogenéticos e evolutivos da tribo e dentro da família Arecaceae. Palavras-Chave: Arecaceae. Filogenia. Açaí. Genética de cloroplastos. Diversidade genética.Item Importância fisiológica dos transportadores mitocondriais de adenilatos AACs em Arabidopsis thaliana(Universidade Federal de Viçosa, 2019-03-11) Batista, Amanda Lima; Nesi, Adriano Nunes; http://lattes.cnpq.br/5734266643442378A mitocôndria é a organela responsável pela maior parte do fornecimento do ATP necessário para os processos metabólicos de manutenção do crescimento e respostas a vários estresses. O transporte de adenilatos (AMP, ADP e ATP) através da membrana mitocondrial interna é mediado por proteínas carreadoras especializadas, dentre as quais se encontram os carreadores do tipo antiporte ADP/ATP (AAC), que exportam o ATP para o citosol e, simultaneamente, importam o ADP para a matriz mitocondrial. Em Arabidopsis thaliana, são encontradas as isoformas AAC1, AAC2 e AAC3, cujos papeis fisiológicos ainda permanecem desconhecidos. Neste trabalho, avaliou-se em Arabidopsis thaliana o papel dos transportadores mitocondriais de ADP/ATP, denominados AtAAC1, AtAAC2 e AtAAC3. Para tal, foram utilizadas linhagens mutantes homozigotas com baixa expressão obtidas por inserção do T-DNA. Estas plantas foram caracterizadas a nível fisiológico e bioquímico. A análise do padrão de expressão dos genes AACs em plantas selvagens em condições ideais de cultivo demonstrou que de fato eles provavelmente desempenham papeis fisiológicos distintos em função do tecido e estágio do desenvolvimento. O gene AAC1 se apresentou como a isoforma mais abundante, independente do tecido e estágio do desenvolvimento. O AAC2 e o AAC3 tiveram expressão mais relevante em tecidos relacionados à fase reprodutiva, tais como grãos de pólen, flores e síliquas. Análise da expressão demonstrou que, na ausência do gene AAC2, ocorre regulação positiva dos demais transportadores de adenilatos da célula. Os mutantes para os genes AAC1, AAC2 e AAC3 exibiram maiores taxas de respiração noturna em relação a plantas WT sem apresentarem alterações na assimilação líquida de carbono e no crescimento. Adicionalmente, a quantificação metabólica nas plantas mutantes das três isoformas apontou tendência de maior acúmulo nos teores de aminoácidos, proteínas, glicose, frutose, sacarose e amido ao longo do período luminoso e alto consumo dos mesmos durante o período noturno. Também foram observadas maiores razões de poder redutor [NAD(P)H/NAD(P) + ] em mutantes para o gene AAC1, AAC2 e AAC3 comparado ao WT. Tomados em conjunto, os resultados sugerem que, esses transportadores ADP/ATP estão envolvidos principalmente no metabolismo do processo respiratório, balanço redox e concentrações de metabólitos nitrogenados e carbonados. Assim, pode-se sugerir que a dinâmica distribuição das moléculas de adenilato, promovida por estes transportadores, tenha vipapeis relevantes na sincronia entre o metabolismo diurno e noturno em plantas, contribuindo assim para a manutenção do steady-state celular, por mecanismos que precisam ser investigados. Para tal, é necessário, aprofundar a compressão do papel destes transportadores nos tecidos vegetais e condições adversas bem como o papel de enzimas chave que atuam no processo.Item Bixin biosynthesis in annatto (Bixa orellana L.) leaves cultured in vitro: influence of irradiance, spectral light quality and the methyltransferase inhibitor 5-azacytidine(Universidade Federal de Viçosa, 2019-02-25) Faria, Daniele Vidal; Otoni, Wagner Campos; http://lattes.cnpq.br/5350053305517459Annatto (Bixa orellana L.) is an important functional food and the unique exploited source for the production of natural dye bixin and norbixin, widely used in the food, pharmaceutical, cosmetic textile and othes industries. The bixin are produced in all plant tissues and accumulated in secretory structures, enabling use the in vitro tissue culture for micropropagation and study of the bixin pathway in the other tissues. However, its biosynthesis pathway and regulation are still not well understood. The genes carotene cleavage dioxygenase (CCD4), aldehyde dehydrogenase (ALDH) and SABATH family methyltransferase (SABATH) are involved with the bixin biosynthesis, since they are overexpressed in immature seeds and are related to carotenoids and apocarotenoids accumulation. Treatments with demethylating agents, such as 5-azacytidine (5-AZA) were previously related to an increased production of secondary compounds and used to study secondary metabolism pathways in plants. The light are characterized by irradiance, wavelength or quality and direction, all these factor can influence in development, growth and in several physiological processes such as in the production of plant secondary metabolites in vitro. Aiming to study the influence of DNA demethylating compound on the bixin pathway in B. orellana cv. Piave Vermelha leaves, we evaluated for the first time the effect of 5-AZA in the global methylation, the expression of some bixin pathway candidate genes, as well as the bixin content, chlorophylls and total carotenoids in the leaves of B. orellana in vitro grown plants. The temporary exposure of shoots apexes cultured in vitro to the demethylating compound 5-AZA did not affect the genome global methylation, chlorophylls and total carotenoid content in leaves of B. orellana. However, plants submitted to 5-AZA showed downregulation of SABBATH family genes and increased the bixin content in the leaves, suggesting that this methyltransferase inhibitor can direct regulate the biosynthesis pathway and the production of bixin in B. orellana. In addition, aiming to study the influence of different light conditions in the in vitro culture of B. orellana, we analysed for the first time the effect of irradiance and light quality on shoot apexes cultured in vitro. The number of leaves per plant, stomatal density, leaf area and leaf expansion, chlorophylls, total carotenoids, malondialdehyde (MDA) and bixin content were analysed in the leaves of B. orellana ‘Piave Vermelha’ and ‘UESB74’ cultured in vitro. The fist produces 1.6-fold more bixin in leaves than the latter and visibly higher bixin content in the seeds. The stomata cells in the leaves of both cultivars were in paracytic arrangement, whit peltate trichomes predominant along the adaxial and abaxial surfaces of the leaf. For in vitro culture of ‘Piave Vermelha’ the blue/red LED light was the best, on the other hand for ‘UESB74’, the culture in fluorescent light is indicared, if the use fluorescent light is chosen for both varieties, are indicated the irradiance of 50 μmol m -2 s -1 is the must recommented. This work opens perspectives about the regulation of the pathway and the heterogeneity of the biosynthesis pathway of bixin.Item Salt stress and UV-B radiation modulate growth, physiology and 20-hydroxyecdysone contents in Brazilian-ginseng [Pfaffia glomerata (Spreng.) Pedersen](Universidade Federal de Viçosa, 2019-02-26) Felipe, Sérgio Heitor Sousa; Otoni, Wagner Campos; http://lattes.cnpq.br/8684935070546979The phytoecdysteroid 20-hydroxyecdysone (20E) is a secondary metabolite with high agrochemical, biotechnological and pharmacological potential, produced only by certain plant species. However, in relation to 20E, it is emphasized that: (i) the biosynthetic pathway is not fully elucidated in plants; (ii) it is not clear its real function in plants; (iii) there are few morphophysiological and molecular studies in plants that produce this metabolite; and (iv) there is a need to investigate the induction, biosynthesis, regulation and translocation of this metabolite in plants. In this sense, two experiments were performed aiming to evaluate the impact of salt stress and UV-B radiation on growth, physiology, expression of key genes involved in the biosynthesis and the 20E content in Pfaffia glomerata. In the first experiment, accession 43 (A43) plants with 40-day-old grown in greenhouse were exposed to 0-, 120-, 240-, 360- and 480-mM sodium chloride (NaCl) for 11 consecutive days. In the second experiment, two accessions (A22 and A43) plants with 20-day-old grown in in vitro were exposed to 0-, 2- and 4-h UV-B radiation for 20 consecutive days. Mild salt stress (i.e., 120 mM NaCl) increased 20E concentrations in the leaves (47%) relative to the control, with no significant effect on photosynthesis and biomass accumulation. In contrast, plants under severe salt stress (i.e., 240 to 480 mM NaCl) did not increase 20E concentrations compared to the control. Additionally, severe salt stress caused marked damage in biomass accumulation and photosynthetic performance in parallel with the nutritional imbalance. To combat severe salt stress, P. glomerata plants displayed an increase in salicylic acid levels, antioxidant enzyme activities and osmoregulatory status (e.g., glucose, fructose, total amino acids, and proline). UV-B radiation differentially impacted the accessions A22 and A43. In A22, 4 h of exposure reduced biomass accumulation and electron transport rate, on the other hand, increased antioxidant activity (e.g., peroxidases), while A43 did not vary for these characteristics. Besides, only A22 increased the 20E concentration under 2 and 4 h of UV-B in leaves (28 and 21%, respectively) and roots (16 and 13%, respectively). This contrasting performance between A22 and A43 to UV-B radiation can be explained by A43 displayed 56% more anthocyanin to the former, a possible defense against UV-B. In both experiments, the production of 20E was accompanied by an upregulation of Spook and Phantom genes. The results of this work bring an unprecedented better understanding of the 20E regulation under conditions of abiotic stresses (salt stress and UV-B radiation). Finally, we provide findings that can be applied to increase 20E levels and contribute to the development of biotechnology, pharmacology and ex vitro and in vitro culture of the species.Item The role of 2-oxoglutarate dehydrogenase during water deficit and recovery in Arabidopsis thaliana(Universidade Federal de Viçosa, 2018-02-18) Vargas, Jonas Rafael; Nesi, Adriano Nunes; http://lattes.cnpq.br/9028236058582130To deal with periods of water limitation, plants use different mechanisms. Among them, stomatal closure and proline accumulation are the major ones during stress exposure. After stress, proline is degraded releasing glutamate in the mitochondrial matrix. The glutamate is metabolized by different metabolic pathways and may: (i) participate in nitrogen metabolism, being used for ammonia assimilation under the action of enzymes like Glutamine synthetase (GS) and Glutamine 2-oxoglutarate aminotransferase (GOGAT), (ii) being reintroduced in the tricarboxylic acid cycle (TCA cycle) as succinate via GABA shunt activity or (iii) enter the TCA cycle as 2-oxoglutarate (2-OG) when undergoing the action of the enzyme glutamate dehydrogenase. 2-OG is converted into succinyl-CoA by the action of the enzyme 2-oxoglutarate dehydrogenase (2-OGDH). In order to understand the importance of 2-OGDH during water deficit and stress release, two T-DNA insertion lines with low expression of the E1 subunit of 2-OGDH encoding gene, e1-ogdh1.1 and 1.2 were submitted to drought conditions for 22 days and then, after rewatering, three days of recovery period. This work revealed that the TCA cycle goes through downregulation in such a way that allows plants to cope with water deficit and that following recovery period its activity is reestablished. Furthermore, it was observed that the reduction in the activity of 2-OGDH did not demonstrate great impact in the metabolism during the implementation and recovery of water deficit. Keywords: abiotic stress; metabolism; proline; TCA cycle; 2-OGDH.Item Morpho-physiological evaluation of Pfaffia glomerata (Spreng.) Pedersen accessions grown under photoautotrophy and water stress conditions(Universidade Federal de Viçosa, 2019-02-28) Chagas, Kristhiano; Otoni, Wagner Campos; http://lattes.cnpq.br/2247931839982225This study aimed to evaluate the morpho-physiological aspects of Pfaffia glomerata (Spreng.) Pedersen accessions grown under photoautotrophy and water stress conditions. In order to address that three experiments were conducted. In the first experiment, diploid (Ac 04, 22 and 43) and synthetic polyploid (Poly 28, 60, 68 and 74) accessions of P. glomerata were grown in vitro under photoautotrophy on a sugar-free MS-based medium, using cellulose and vermiculite (1:2 ratio) as supporting material, and maintained in a growth room at 25 ± 2°C and 60 μmol m -2 s -1 irradiation, provided by red/blue led lamps for 30 days. In the second experiment, two P. glomerata accessions (Ac 22 and 43) propagated in vitro were acclimatized in a greenhouse and submitted to moderate and severe water deficit for 15 days, after 7 days were rehydrated and performed analysis in conditions stressed and recovery. In the third experiment, the effects water deficit elicited in vitro by supplementing a MS-based medium withof polyethyleneglycol (PEG 6000) at 0, 0.1, 0.2, 0.3%) evaluated by comparing plants grown for 20 days under stress and after 7 days rehydration. Here, a versatile light chamber formed by 8 high brightness white LEDs disposed on the inside wall of an expanded polystyrene (EPS) box and used with source photosynthetic photon flux (600 μmol m -2 s -1 ) in measurements of photosynthesis in vitro. Under photoautotrophic conditions, the polyploids exhibited lower leaf number, and thicker and more expanded leaves, increased stomata size and reduced stomata density compared to the diploid counterparts. Even with the morphological differences, all assayed accessions showed average in vitro photosynthetic rate of 7.31 μmol m -2 s -1 and Fv/Fm 0.79. The Ac 04 presented and 20-hydroxyecdysone (20E) contents. The drought stress led to a marked decrease in biomass, height, leaf expansion, epidermis and mesophyll, and increased stomatal density, for both accessions (Ac 22 and Ac 43) raised in vitro and ex vitro. The photosynthetic rate and dark respiration increased in stressed plants in greenhouse, whereas the addition of PEG in vitro decreased photosynthesis. On topo of that, the water deficit led to increased contents of abscisic and salicylic acid, stimulated antioxidant enzyme activities, and osmoregulatory status, but to a decreased zeatin levels. The Ac 43 maintained under full irrigation exhibit higher content and field yield of 20E than Ac 22, both accessions the water deficit in greenhouse and in vitro increased 20E levels and decrease in production total of metabolite. This work proposes an innovative, practical and efficient LED-based apparatus to efficiently evaluate the photosynthetic rates of vitroplants, thus providing foundations to expand the understanding of the acquisition of photosynthetic competence during plant development under photoautotrophic in vitro environment. These findings also provide a better understanding of the different morpho-physiological responses of synthetic polyploids P. glomerata under photoautotrophy, and acclimation strategies adopted by the species that enable drought tolerance and pave the way for further studies that can lead to improved 20E production, a bioactive compound with high economic value and biochemical interest. Keywords: Light source; gas exchange; synthetic polyploidy; Brazilian ginseng; 20- hydroxyecdysone; endogenous hormone levels; water stressItem Functional analysis of the thioredoxin system during seed germination in Arabidopsis thaliana(Universidade Federal de Viçosa, 2019-03-29) Nascimento, Carolina Pereira; Nesi, Adriano Nunes; http://lattes.cnpq.br/3331610618877369A series of processes occurs during seed formation, including remarkable changes from early development to the end of germination. The changes associated with processes initiated mainly after seed imbibition are usually characterized by extensive changes in redox state of seed reserve proteins and of pivotal enzymes for protein mobilization and usage. Such changes in redox state are often mediated by Thioredoxins (Trxs), which are protein oxiredutases capable of catalyzing the reduction of disulfide bonds in target proteins, thereby regulating their structure and function. Here, we analyzed the previously characterized mutants of NADPH-dependent Trx reductase A and B (ntra ntrb), two independent mutant lines of mitochondrial thioredoxin o1 (trxo1) and two mutant thioredoxin h2 (trxh2) mutant lines. Our results indicate that plants deficient for the NADPH-dependent thioredoxin system are able to mobilize their reserves, but at least partially fail to use these reserves during germination, thereby leading to lower availability of energy substrates than wild type seeds. Trx mutants also show decreased activity of regulatory systems needed to maintain cellular homeostasis. Moreover, we observed reduced respiration in mutant seeds and seedlings, which in parallel with an impaired energy metabolism, disrupts core biological processes responsible for proper germination and early development of Trx mutants. In conclusion, the results suggest that the lack of thioredoxin induces a substantial adaptation in seeds and seedlings, which undergo a metabolic reprogramming to adapt to a new redox state.Item In vitro neoformation of organs in Bixa orellana L.: morphoanatomy, cloning and characterization of pluripotency-associated putative transcription factors(Universidade Federal de Viçosa, 2016-07-28) Correia, Ludmila Nayara de Freitas; Otoni, Wagner Campos; http://lattes.cnpq.br/0302170800368756Pluripotency is the characteristic of plant cells that allows a single cell to originate the tissues that will compose the plant body. Organogenesis is a regeneration pathway with basis of these principles to induce organ neoformation. The plant growth hormones associated with molecular events are essential to the success of these morphogenic pathways. Thus, the objectives of this study were: to evaluate the morphogenic response in vitro from different explants of Bixa orellana submitted to organogenic induction; to characterize the cytological changes that occur during shoot and root formation, as well as to follow the mobilization of reserves, and to isolate and characterize genes expressed during the organogenic events. To assess the shoot formation, hypocotyls, injured hypocotyls, rooted hypocotyls with reversed polarity, and petiolate leaves were inoculated in JADS medium, supplemented with B5 vitamins, sucrose (3% w/v), myo- inositol (0.01% w/v), agar (0.6% w/v) and 4.56 μM zeatin, or 2.07 μM meta-topolin, or 4.14 μM meta-topolin. Samples with 0, 3, 6, 9, 18, 21, 24 and 30 days were collected for light microscopy, scanning electron microscopy, and histochemical tests following specific protocols. In order to assess the root formation, plantlets were inoculated in JADS medium in similar conditions as cited above, but with 0 or 2.46 μM indolilbutyric acid (IBA). After 0, 2, 4, 6, 8, 10, 18 and 20 days, samples were collected to perform the same analyses mentioned before. Total RNA was extracted from the organogenic material, from which the cDNA was obtained and used as a template for the amplification of coding sequences using degenerate primers for BABY BOOM (BBM) and SHOOT MERISTEMLESS (STM). It was observed that in Bixa orellana zeatin and meta-topolin induced shoot formation, but the injured hypocotyls as well as rooted hypocotyls with reversed polarity optimized the process when compared with hypocotyl and petiolate leaves. The first cell divisions were observed in the first weeks of culture in induction medium, especially in explants cultured in medium supplemented with zeatin. After 30 days of cultivation, zeatin and meta-topolin induced the formation of leaf primordia in the evaluated explants. Proteins were evidenced mainly in rooted hypocotyls and petiolate leaves. Starch grains were found in all types of explant evaluated, and a gradual increase in the concentration of this reserve compound was observed during the induction period. The neutral red test did not indicate the presence of lipids during the organogenic process. Plantlets inoculated in JADS with IBA have cell divisions after four days of culture, originating lateral root primordia. The maintenance in the induction medium supplemented with IBA for 20 days led to the formation of lateral roots. In the same period, lateral root primordia were observed in the control. The histochemical tests evidenced the presence of protein, which were consumed during the organogenic event, in addition to starch grains and lipids present in all evaluated days. Consensus sequence obtained from BBM and STM degenerate primers were cloned and sequenced. The consensus sequences obtained were compared to non-redundant protein databases NCBI, Phytozomee TAIR, using the BLAST algorithm. The analysis and alignment of sequences yielded three contigs similar to members of APETALA2-like family, especially BBM, WRINKLED (WRI) and AINTEGUMENTA (ANT), and three contigs with high similarity to transcription factors of Class I KNOX, especially STM. These results demonstrate the morphogenetic responses of different types of explants subjected to induction medium, and the possible members of the AP2-like and Class I KNOX families cloned from the analyzed sequences, which are associated with the acquisition of competence for in vitro organogenesis in Bixa orellana.Item Physiological, hormonal and metabolic alterations caused by selenium in rice seedlings(Universidade Federal de Viçosa, 2019-07-30) Malheiros, Rafael Soares Pozzi; Ribeiro, Dimas Mendes; http://lattes.cnpq.br/0869713643496189Selenium (Se) can alter the growth of some plant species and causes changes in levels of plant hormones, such as auxin and ethylene. However, the impact of Se supply on relationships between hormones biosynthesis and primary metabolism during growth of rice (Oryza sativa L.) seedlings is poorly understood. Thus, the hypothesis that Se induces changes in the interactions between auxin and ethylene to modulate primary metabolism and growth of rice seedlings was investigated. The application of selenite did not affect the of growth shoot of seedlings, but promoted the elongation of the primary root with reduction in the number and length of the lateral roots. There was a decrease in the concentrations of ethylene, 1- aminocyclopropane-1-carboxylic acid (ACC) and indole-3-acetic acid (IAA) in roots of rice seedlings treated with selenite as compared with the control. Selenite led to decreased expression of genes associated with the biosynthesis of auxin and ethylene, concomitantly with reduced production of these hormones by the roots. Moreover, selenite decreased the abundance of transcripts encoding auxin transport proteins. Treatment with IAA overrode the repressive effect of selenite on lateral root growth. The ethylene synthesis inhibitor L-α-(2- aminoethoxyvinyl)-glycine (AVG) increased elongation of primary root, whereas the ethylene precursor ACC resulted in the opposite effect. Moreover, soluble sugars accumulate in roots under selenite treatment. Together, these findings suggest that selenite affects primary and lateral root development by blocking ethylene and auxin biosynthesis, respectively. Experiments with organic Se showed that seleno-L-methionine (SeMet) at low concentration increased concentrations of hydrogen peroxide and superoxide anion production, inhibiting auxin biosynthesis and increasing ethylene production in both shoot and root. The effect of SeMet on seedlings was mediated by the inhibition of the abundance of transcripts encoding auxin transport and cell expansion proteins. Moreover, SeMet led to increased respiration, which was positively correlated with organic acids consumption, but negatively with sugars consumption, thereby decreasing seedling growth. In contrast with SeMet treatment, L- methionine did not affect reactive oxygen species production, hormone biosynthesis and growth of seedlings, indicating an exclusive Se effect. Treatment with 1,4-diazabicyclooctane (DABCO), a singlet oxygen scavenger, overrode the repressive effect of SeMet in seedling growth. It is concluded that Se regulates physiological and metabolic processes in rice seedlings are dependent on the form of Se supplied. Keywords: Cell expansion. Primary metabolism. Hormonal regulation. Oryza sativa L.Item Caracterização morfoanatômica, transcriptômica e estudo da aquisição de competência para a organogênese in vitro de espécies do gênero Melocactus (Cactaceae)(Universidade Federal de Viçosa, 2019-02-20) Silva, Gabriela Torres da; Otoni, Wagner Campos; http://lattes.cnpq.br/2974906293894879O Brasil é área prioritária na conservação da família Cactaceae por possuir grande número de espécies endêmicas. No entanto, fatores como degradação do habitat e coleta ilegal para comercialização como ornamental tem levado algumas espécies dessa família ao perigo de extinção, dentre estas espécies estão Melocactus paucispinus e M. glaucescens. Neste contexto, as técnicas de cultura de tecidos são uma importante ferramenta, pois permitem a propagação in vitro de material vegetal em larga escala, fornecendo uma alternativa à retirada dos indivíduos do seu habitat para a comercialização como ornamental. Contudo, a propagação in vitro de Melocactus apresenta alguns desafios, como o baixo número de brotos por explante, de brotos com variação morfológica e a ocorrência de variação somaclonal. Apesar do crescente interesse dos Melocactus como ornamental e da sua forma de propagação in vitro ser via cladódio, pouco se sabe sobre os aspectos morfofisiológicos relacionados à aquisição de competência para a organogênese in vitro dos membros deste gênero. Com o objetivo de aumentar o conhecimento sobre os processos da organogênese em espécies do gênero Melocactus, foi realizada a caracterização anatômica do cladódio de M. glaucescens e M. paucispinus, assim como a análise da ploidia das regiões do cladódio e a microtomografia de raio-X. As duas espécies de Melocactus estudadas apresentaram o mesmo padrão de organização dos tecidos e picos de ploidia, onde a periferia do cladódio e a medula apresentaram quatro picos de ploidia (2C, 4C, 8C e ~16C), as raízes são diploides e o córtex do cladódio apresentou um pico a mais de ploidia (~32C). A mixoploidia do cladódio foi atribuída ao programa de formação dos diferentes tecidos que compõem este órgão, o qual possui como uma das principais funções o armazenamento de água. As células com alta ploidia passaram por endociclos que aumentaram seus conteúdos de DNA, o que permite que o volume de armazenamento de água nos vacúolos seja maior para que assim possam desempenhar sua função de parênquima aquífero. A análise de microtomografia de raio-X mostrou que o diâmetro das células da região do córtex é maior do que na periferia e na medula do cladódio, corroborando com os dados de ploidia. Para compreender as modificações anatômicas durante a organogênese de M. glaucescens, foi realizada a caracterização anatômica de explantes cultivados na ausência de regulador de crescimento e explantes cultivados na presença de 1,34 μM de ácido naftaleno acético (ANA), 17,76 μM de 6- benzilaminopurina (BA) e com as aréolas feridas. Além disso, foi realizada a análise de expressão do gene SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (MgSERK-like) nos mesmos tratamentos. Foi observada a formação de brotações derivadas da ativação da região meristemática das aréolas, assim como de regiões mais internas do cladódio, sendo que mais meristemoides foram observados no córtex dos explantes que foram submetidos à ação de reguladores de crescimento e ferimento. Este tratamento também mostrou elevado número de brotações, ocorrência de variação morfológica e expressão do gene MgSERK-like em todos os períodos analisados da organogênese. Alterações no padrão de expressão durante a organogênese in vitro também foram observadas nas análises de expressão diferencial (ED) de explantes antes e após a indução de organogênese na presença de 1,34 μM de ANA, 17,76 μM de BA e com as aréolas feridas. A análise do transcriptoma mostrou que os explantes antes da indução da organogênese apresentavam o metabolismo mais comprometido com o metabolismo primário, principalmente com a fotossíntese, além da alta expressão do fator de transcrição TCP, o qual é responsável pela forte dominância apical nessa espécie que não apresenta ramificações laterais naturalmente. As análises no Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, BiNGO e Plant Transcription Factor Database demonstram que o metabolismo nos explantes submetidos à organogênese é modificado e concentrado em genes relacionados com mitocôndria, parede celular, retículo endoplasmático, organização celular e biogênese, o que tem relação com o aumento da síntese de proteínas para dar suporte na divisão celular e formação de parede durante a regeneração. As análises de ED também indicam que os tecidos submetidos à organogênese apresentaram grande potencial na produção de compostos do metabolismo secundário, o que amplia as possibilidades de aplicação das culturas in vitro de M. glaucescens.