Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
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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 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.Item Manipulation of source-to-sink ratios in girdled coffee branches evidences lack of photosynthetic down-regulation: the interplay of photosynthesis with respiration and photorespiration pathways and amino acid metabolism(Universidade Federal de Viçosa, 2016-02-25) Avila, Rodrigo Teixeira; Matta, Fábio Murilo da; http://lattes.cnpq.br/6404622647636394We aimed to gain a better understanding on how the regulation of photosynthesis in coffee depends on sink activity or carbohydrate build-up in source leaves and how the coffee tree adjusts its photosynthetic performance and primary metabolism to varying source-to-sink ratios. For these purposes, we use integrative approaches combining gas- exchange and chlorophyll a fluorescence measurements, analyses of carbohydrates and major metabolites, activities of a range of enzymes and the expression of some genes encoding for key enzymes of the carbon metabolism to achieve a holistic view of the whole leaf metabolism in response to long-term source-to-sink manipulation. We designed a field experiment by girdling coffee branches that were further manipulated by controlled defoliation and/or defruiting so that three highly varying source-to-sink ratios were created. We found that under remarkably high source-to-sink ratios photosynthesis rates were chiefly limited by diffusive factors (that were apparently unrelated to whole-leaf abscisic acid) with no apparent signs of feedback down- regulation. Lack of down-regulation was associated with an enormous capacity for starch accumulation coupled with maintenance of low levels of soluble sugars. Chronic Chronic photoinhibition and photodamage could be avoided through adjustments in leaf photochemistry, photorespiration and respiration amongst other processes. No major metabolic reprograming was found at the level of key enzymes associated with carbon metabolism. Metabolic adjustments in source leaves were more evident under high-sink demand conditions and centered more on nitrogen metabolism than on carbon metabolism. In conclusion, our results offer novel insights on the high coordination between the source supply and sink demand in coffee trees, with no evident signs of photosynthetic down-regulation even under dramatically low-sink conditions.Item Differential response of sweet potato cultivars to cold storage(Universidade Federal de Viçosa, 2019-07-18) Araújo, Nícolas Oliveira de; Finger, Fernando Luiz; http://lattes.cnpq.br/2380449284919979Cold-induced sweetening (CIS) and chilling injury symptoms are the main physiological disorders that compromise the quality of sweet potato roots stored at suboptimal temperatures. The manifestation of chilling-induced physiological disorders depends on the temperature, time of exposure to the stress condition and chilling sensitivity level of the genotype. Therefore, the objective of this work was to describe differences in chilling sensitivity among sweet potato cultivar roots; evaluate the involvement of invertases and sucrose synthase in CIS; describe the impact of CIS on non-enzymatic darkening of sweet potato chips; and to evaluate the importance of the enzymatic and non-enzymatic antioxidant system in the presence or not of chilling injury symptoms in sweet potato roots. Sweet potato roots of the cultivars BRS Rubissol, BRS Cuia and Beauregard were stored at 6 or 13 °C for up to 60 days. The roots of the cultivar Beauregard showed higher chilling injury tolerance when compared to the cultivars BRS Rubissol and BRS Cuia. The CIS was shown at 6 °C due to the accumulation of non- reducing sugars, and the low invertase activity in the cultivars BRS Rubissol and BRS Cuia. On the other hand, the CIS in the Beauregard cultivar was characterized by the high invertase activity and the relatively equivalent accumulation amidst reducing and non-reducing sugars. Sucrose synthase activity was induced only in the cold-sensitive cultivars BRS Rubissol and BRS Cuia when stored at 6 °C, probably as an energy conservation mechanism. Non-enzymatic darkening of sweet potato chips was more influenced by the non-reducing sugar content when compared to reducing sugars. In contrast to the cultivars BRS Rubissol and BRS Cuia, the roots of the Beauregard cultivar did not exhibit symptoms of chilling injury by reducing oxidative stress at 6 °C through increased catalase and ascorbate peroxidase activities, as well as by increasing the content of carotenoids. Keywords: Ipomoea batatas. Invertases. Sucrose synthase. Sweetening. Chilling injury.