Renato Rodrigues Ferreira

Effects of Cadmium on Antioxidant Enzyme Activities in Sugar Cane

Sugar cane (Saccharum officinarum L. cv. Copersucar SP80-3280) seedlings were grown in nutrient solution with varying concentrations (0, 2 and 5 mM) of cadmium chloride for 96 h. Leaves were analysed for catalase (CAT), glutathione reductase (GR) and superoxide dismutase (SOD) activities. Although a clear effect of CdCl2 on plant growth was observed, the activity of SOD was not altered significantly. However, the CAT activity decreased as the concentration of CdCl2 increased. GR exhibits a significant increase in activity at 2 and 5 mM CdCl2. CAT and SOD isoenzymes were further characterised by analysis in non-denaturing PAGE. Activity staining for SOD revealed up to seven isoenzymes in untreated control and 2 mM CdCl2 treated plants, corresponding to Cu/Zn-SOD isoenzymes. At 5 mM CdCl2, only six Cu/Zn-SOD isoenzymes were observed. No Fe-SOD and Mn-SOD isoenzymes were detected. For CAT, one band of activity was observed.

CHANGES IN ANTIOXIDANT ENZYME ACTIVITIES IN SOYBEAN UNDER CADMIUM STRESS

Soybean (Glycine max L.) seedlings were grown in a hydroponic system containing nutrient solution with varying concentrations (0, 0.01, 0.5 mM) of cadmium (Cd) for a 48 h period. Roots and leaves were analyzed for catalase, glutathione reductase, and superoxide dismutase activities. Although a clear effect of Cd on plant growth was observed, the activities of catalase and superoxide dismutase were not altered significantly in the roots or leaves at all concentrations tested. Glutathione reductase did not exhibit any variation in activity in leaves, however, in roots an increase in activity was observed at 0.5 mM Cd. Catalase and superoxide dismutase isoenzymes were further characterized by analysis in non-denaturing PAGE. Activity staining for superoxide dismutase (SOD) revealed seven isoenzymes in leaves and eight isoenzymes in roots, corresponding to Mn-SOD and Cu/Zn-SOD. No Fe-SOD isoenzymes were observed. For catalase, one band of activity was observed in leaves and roots. Although no significant variation was observed in leaf tissue, in roots the 0.5 mM Cd treatment exhibited a slight increase in catalase activity. The results suggest that in soybean, glutathione reductase is stimulated by Cd in roots, to produce reduced glutathione to be used in the synthesis of phytochelatins or possibly as a response to the generation of reactive oxygen species induced by Cd.

Cadmium stress in sugar cane callus cultures: Effect on antioxidant enzymes

Catalase (CAT) and superoxide dismutase (SOD) are antioxidant enzymes which are important in the metabolism of reactive oxygen species (ROS), and can be induced by environmental stresses including cadmium (Cd), a heavy metal toxic to living organisms. Sugar cane (Saccharum officinarumL.) in vitro callus cultures were exposed to CdCl2 and the activities of CAT and SOD were analysed. Lower concentrations of CdCl2, such as 0.01 and 0.1 mM caused a significant increase in callus growth, whereas 0.5 and 1 mM CdCl2 strongly inhibited growth of the callus cultures, but only after 9 days of CdCl2 treatment. Red-brown patches were also observed in calluses exposed to 0.5 and 1 mM CdCl2. Calluses grown in 0.01 and 0.1 mM CdCl2 did not exhibit any changes in CAT activity even after 15 days of growth in the presence of CdCl2. However, for calluses grown in higher concentrations of CdCl2 (0.5 and 1 mM), a rapid increase in CAT activity was detected, which was 14-fold after 15 days. Furthermore, up to five CAT isoforms were observed in callus tissue. Total SOD activity did not exhibit any major variation. One Mn-SOD and two Cu/Zn-SOD isoenzymes were observed in callus cultures and none exhibited any variation in response to the CdCl2 treatments. The results suggested that in sugar cane callus cultures, CAT may be the main antioxidant enzyme metabolizing H2O2.

Herbicide selectivity by differential metabolism: considerations for reducing crop damages

A seletividade dos herbicidas e uma tecnologia agricola que tem sido vastamente explorada nas estrategias de controle quimico de plantas daninhas. E resultado da acao conjunta de diversos mecanismos que protegem a cultura da fitotoxicidade dos tratamentos herbicidas, mantendo-a com niveis de injurias aceitaveis agronomicamente, ou mesmo na ausencia destas. O principal mecanismo de seletividade dos herbicidas e o metabolismo diferencial desses produtos entre plantas daninhas e cultivadas, em que, nas situacoes de recomendacao agronomica, as plantas daninhas sao menos habeis em realiza-lo. Neste caso, a fitotoxicidade pode ser entendida como a suplantacao da capacidade maxima de protecao oferecida pelos mecanismos de seletividade ou, considerando o metabolismo como o principal mecanismo, como a superacao da capacidade intrinseca da especie em detoxificar determinada molecula. Considerando-se que o metabolismo de herbicidas envolve gasto de energia, os sintomas de fitotoxicidade caracterizam um segundo gasto energetico que nao deve ser aceito como uma resposta fisiologica natural, portanto pode resultar em perdas de rendimento das culturas. Para evitar ou minimizar as perdas ou injurias as culturas, e necessario que as recomendacoes de herbicidas sejam baseadas em trabalhos de seletividade conduzidos com adequado rigor experimental; bem como e importante a conscientizacao dos agricultores quanto a melhor forma de utilizar cada produto.Herbicide selectivity is an agricultural technology largely exploited in chemical strategies of weed control. The joint action of several protection mechanisms avoids phytotoxicity from herbicide treatment, maintaining the level of agronomically accepted damage to a minimum, or even totally avoiding them. The major mechanism of herbicide selectivity derives from the differential metabolism between weed and crop plant species, with weeds presenting a limited ability to perform it under agronomically recommended conditions. In this case, phytotoxicity can be interpreted as an overcoming of the maximum protection capacity offered by the mechanisms of selectivity, or when considering metabolism as the main factor, the overcoming of the inherent plant ability to detoxify a particular molecule. Considering that herbicide metabolism requires energy disposal, symptoms of phytotoxicity characterize an additional waste of energy that should not be accepted as a natural physiologic response; therefore it might result in yield losses. To avoid or minimize crop losses or damages, it is required that herbicide application recommendations are based on results from rigorously conducted selectivity experiments, as well as that there is an increase in the awareness of growers about the best use of each product.

Are high-lysine cereal crops still a challenge?

The essential amino acids lysine and threonine are synthesized in higher plants via a pathway starting with aspartate that also leads to the formation of methionine and isoleucine. Lysine is one of most limiting amino acids in plants consumed by humans and livestock. Recent genetic, molecular, and biochemical evidence suggests that lysine synthesis and catabolism are regulated by complex mechanisms. Early kinetic studies utilizing mutants and transgenic plants that over-accumulate lysine have indicated that the major step for the regulation of lysine biosynthesis is at the enzyme dihydrodipicolinate synthase. Despite this tight regulation, recent strong evidence indicates that lysine catabolism is also subject to control, particularly in cereal seeds. The challenge of producing crops with a high-lysine concentration in the seeds appeared to be in sight a few years ago. However, apart from the quality protein maize lines currently commercially available, the release of high-lysine crops has not yet occurred. We are left with the question, is the production of high-lysine crops still a challenge?

Development of microsatellite primers for Jatropha curcas (Euphorbiaceae) and transferability to congeners

PREMISE OF THE STUDY Microsatellite primers were developed for Jatropha curcas (Euphorbiaceae), a tree species with large potential for biofuel production, to investigate its natural genetic diversity and mating system to facilitate the establishment of tree improvement and conservation programs. METHODS AND RESULTS Using a protocol for genomic library enrichment, 104 clones containing 195 repeat motifs were identified. Primer pairs were developed for 40 microsatellite loci and validated in 41 accessions of J. curcas from six provenances. Nine loci were polymorphic revealing from two to eight alleles per locus, and six primers were able to amplify alleles in the congeners J. podagrica, J. pohliana, and J. gossypifolia, but not in other Euphorbiaceae species, such as Hevea brasiliensis, Manihot esculenta, or Ricinus communis. CONCLUSIONS The primers developed here revealed polymorphic loci that are suitable for genetic diversity and structure, mating system, and gene flow studies in J. curcas, and some congeners.

Tolerância diferencial de variedades de cana-de-açúcar a estresse por herbicidas

This work was carried out with the objective of screening for tolerance response of SP and CTC sugarcane varieties to application of ten herbicides commonly recommended to weed management in this crop. Two trials were evaluated with factorial design between the sugarcane varieties and eleven herbicide treatments. In the first experiment, seven SP varieties were used (factorial 7 x 11): SP80-1842, SP80-3280, SP83-2847, SP87-344, SP87-396, SP89-1115 and SP90-3414. In the second experiment, six CTC varieties were evaluated (factorial 6 x 11): CTC1, CTC2, CTC3, CTC4, CTC5 and CTC6. The post-emergence-applied herbicide treatments were: ametryn, ametryn + trifloxysulfuron-sodium, clomazone, diuron + hexazinone, isoxaflutole, imazapic, 2,4-D, tebuthiuron, sulfentrazone, MSMA and check without application. The variables evaluated were: fresh mass, height, SPAD index and tillering: Valves here considered as relative percentage to the untreated control. Differential tolerance of sugarcane varieties was observed regarding to application of the tested herbicides. SP80-3280 and CTC2 were the most tolerant varieties to herbicide application, and might have this characteristic exploited by sugarcane breeding programs.

Nutritional Quality of Sorghum Seeds: Storage Proteins and Amino Acids

One sorghum commercial genotype (MASSA 03) and nine ICRISAT high-lysine genotypes from India were analyzed for storage protein content, distribution profile, and soluble amino acid concentrations. Storage proteins fraction were extracted and separated by SDS-PAGE. Soluble amino acids contents were determined by HPLC. Variations in intensity and appearance and disappearance of protein bands were observed among the sorghum genotypes suggesting genetic variability. Amino acid profile also indicated large variations in the amino acid concentrations. The high lysine and threonine soluble concentrations observed in the seeds of the sorghum genotypes encouraged the use of these genotypes as potential food source due to the better balanced amino acids profile.

Lysine catabolism: flow, metabolic role and regulation

Lysine is an essential amino acid, synthesized in plants in the aspartic acid pathway. The lysine catabolism is performed by the action of two consecutive enzymes, lysine 2-oxoglutarate reductase (LOR) and saccharopine dehydrogenase (SDH). The steady state of lysine is controlled by both, synthesis and catabolism rates, with the final soluble lysine concentration in cereal seeds a direct result of these processes. In the last 40 years, the enzymes involved in lysine biosynthesis have been purified and characterized from some plant species such as carrot, maize, barley, rice, and coix. Recent reports have revealed that lysine degradation might be related to various physiological processes, for instance growth, development and response to environmental changes and stress. The understanding of the regulatory aspects of the lysine biosynthetic and catabolic pathways and manipulation of related enzymes is important for the production of high-lysine plants.

Diallelic analysis for lysine and oil contents in maize grains.

Seis linhagens S5 de milho, com diferencas para conteudos de oleo e de lisina nos graos, foram usadas para realizar uma serie completa de cruzamentos dialelicos. Os 15 hibridos resultantes foram cultivados em campo com dois niveis de nitrogenio (10 e 130 kg N ha-1). A capacidade geral de combinacao (CGC) e a capacidade especifica de combinacao (CEC) foram obtidas com o metodo 4, modelo I de Griffing para produtividade de graos e concentracao de lisina e oleo nos graos. Interacao significativa (p < 0.001) foi observada entre CGC e niveis de N para produtividade de graos, indicando selecao de diferentes linhagens para cada nivel de N. Esta interacao nao foi significativa para conteudo de lisina, mas existiu efeito significativo (p < 0.1) da CGC nos dois niveis de N para esta variavel. Os efeitos de CGC e CEC foram nao significativos para conteudo de oleo, contudo, foi observada correlacao positiva entre conteudos de lisina e oleo nos hibridos, nas linhagens e mesmo nas cultivares utilizadas como controle. Os resultados indicam a efetividade da selecao para conteudo de lisina nas linhagens nao opaco de milho estudadas, independente dos niveis de N, e a possibilidade de atingir concomitantemente maiores niveis de oleo e lisina nos graos.