The absorption of free carbohydrates produced by digestion of dietary fiber in monogastric animals was investigated. Previous studies have shown that dietary fiber is partially digested by monogastric animals in its passage through the alimentary canal. However, the ability of monogastric animals to absorb the products of digestion of dietary fiber is uncertain. Male rats of the Sprague-Dawley strain were fed a refined carbohydrate diet in which sucrose comprised 66.6 percent. The urine of rats fed this diet contained only sucrose and its component monosaccharides, glucose and fructose, indicating that the carbohydrate composition of urine reflects the carbohydrate composition of the diet. The rats were then fed diets containing 5 percent guar gum (a galactomannan), 10 percent xylan (a polymer of xylose), or 10 percent wheat bran. The appearance in the urine of the component carbohydrates of the ingested dietary fiber was used as an indication of the absorption of the carbohydrates derived from fiber digestion. The urine of rats fed guar gum contained galactose. Rats fed xylan excreted xylose in the urine. Xylose and arabinose were identified in the urine of rats fed wheat bran. It is postulated that the polysaccharides of dietary fiber are degraded to simple sugars by bacteria in the colon. The results of this study indicate that free carbohydrates produced by digestion of dietary fiber are absorbed in monogastric animals. The potential nutritional and toxicological effects of the absorption of the carbohydrate components of dietary fiber are discussed. / Master of Science

Plants are exposed to many adverse factors during their life cycles. Abiotic stresses are significantly limiting plant growth and development. Abiotic stress response mechanisms involve compatible solute synthesis (e.g. sugars, sugar alcohols and amino acids). The aim of this study was to characterise the responses of plants from Plantago genus to different abiotic stresses (drought, salinity, cold and stress combination). The complete plants grew under in vitro conditions. I compared morphological parameters, selected metabolic parameters (carbohydrates balance and proline accumulation) under optimal conditions and stress exposure. This study was focused on plants from genus Plantago, because they differ from each other in their tolerance to the salinity. Both, the glycophyte and the halophyte species are described within this genus. Plantains produce besides widespread soluble carbohydrates (sucrose, glucose, fructose) also sugar alcohol sorbitol, which has been reported as a significant component of the stress response. In addition, the reaction of plants to different carbon and energy sources was tested. More severe growth inhibition of the glycophyte Plantago lanceolata compared to the halophyte P. maritima was observed under salt treatment. Significant accumulation of sorbitol was observed...

A dose response relationship between carbohydrate (CHO) ingestion and exercise performance has not been consistently reported. Additionally the underlying metabolic and neuromuscular explanations for an improvement in performance with increasing doses of CHO have not been fully explained. In Chapter 2 of this thesis 20 male cyclists completed 2 h of submaximal exercise followed by a time trial task (531 ± 48KJ). Three CHO electrolyte beverages, plus a control (water), were administered during a 2 h ride providing 0, 20, 39 or 64 g CHO·h-1 at a fluid intake rate of 1 L·h-1. Performance was assessed by time to complete the time trial task, mean power output sustained, and pacing strategy used. Mean task completion time (min:sec ± SD) for 39 g·h-1 (34:19.5 ± 03:07.1, p=0.006) and 64 g·h-1 (34:11.3 ± 03:08.5 p=0.004) of CHO were significantly faster than control (37:01.9 ± 05:35.0). The mean percentage improvement from control was -6.1% (95% CI: -11.3 to -1.0) and -6.5% (95% CI: -11.7 to -1.4) in the 39 and 64 g·h-1 trials respectively. The 20 g·h-1 (35:17.6 ± 04:16.3) treatment did not reach statistical significance compared to control (p = 0.126) despite a mean improvement of -3.7% (95% CI -8.8 to 1.5%). These data demonstrate that consuming CHO at a rate between 39 to 64 g·h-1 is likely to be optimal for most individuals looking to utilise a single source CHO as an ergogenic aid during endurance performances lasting less than 3 hrs. Attempts have been made to try and understand the acute metabolic regulation that occurs when ingesting increasing amounts of CHO. However, no one study has fully investigated the metabolic mechanisms underlying graded increments of CHO ingestion. In Chapter 3 we aimed to utilise stable isotopes and blood metabolite profiles to examine the integrated physiological responses to CHO ingestion when ingested at rates throughout the range where performance gains appear greatest. Twenty well-trained male cyclists completed 2 h constant load ride (95% lactate threshold, 185 ± 25W) where one of three CHO beverages, or a control (water), were administered every 15 min, providing participants with 0, 20, 39 or 64 g CHO·h-1 at a fixed fluid intake rate of 1L·h-1. Dual glucose tracer techniques (6,6,2H2 glucose and U13C labelled glucose) were used to determine glucose kinetics and exogenous carbohydrate oxidation (EXO) during exercise. Endogenous CHO contribution was suppressed in the second hour of exercise when consuming 39 and 64 g·h-1 in comparison to 0 g·h-1 (-7.3%, 95%CI: -13.1 to -1.6 and -11.2%, 95%CI: -16.9 to -5.5 respectively). Additionally, consuming 64 g·h-1 suppressed the endogenous CHO contribution by -7.2% (95%CI: -1.5 to -13.0) compared to the 20 g·h-1 treatment. Exogenous CHO oxidation rate increased by 0.13 g·min-1 (95%CI: 0.10 to 0.15) and 0.29 g·min-1 (95%CI: 0.27 to 0.31) when consuming 39 and 64 g·h-1 in comparison to 20 g·h-1 of CHO. Peak exogenous CHO oxidation rates were 0.34 (0.06), 0.54 (0.09) and 0.78 (0.19) g·min-1 for 20, 39 and 64 g·h-1 respectively. Plasma NEFA concentration was 0.10 (95%CI: 0.07 to 0.13), 0.12 (95%CI: 0.10 to 0.16) and 0.16 (95%CI: 0.13 to 0.19) mmol.L-1 higher when consuming 0 g·h-1 in comparison to 20, 39 and 64 g·h-1 respectively. Both 39 and 64 g·h-1 were effective at sparing endogenous CHO stores of which it is estimated that most of this is liver glycogen sparing, but the measured response was highly variable between individuals. Consuming 39 g·h-1 of CHO appears to be the minimum ingestion rate required to have a significant metabolic effect that results in an increase in performance. Recent research has indicated a key role of endogenous CHO sensing and oral glucose sensing in maintaining central drive and peripheral function during endurance exercise tasks. Consuming 39 and 64 g·h-1 of CHO elicits the greatest improvements in performance and also demonstrate a similar metabolic response. The improvement in subsequent time trial performance when consuming 39 and 64 g·h-1 coincided with significant alterations in whole body substrate usage that lead to endogenous CHO sparing at the same ingestion rates. In Chapter 4 we aimed to utilise gold standard neuromuscular function assessment techniques, alongside novel measures, to investigate the effect of consuming different rates of CHO on neuromuscular function during and following prolonged cycling exercise. In a double-blind, randomised cross-over design, well-trained male cyclists (n=20, mean±SD, age 34 ± 10 y, mass 75.8 ± 9 kg, peak power output 394 ± 36 W, V̇O2max 62 ± 9 ml·kg-1·min-1) completed 2 familiarisation trials then 4 experimental trials. Trials involved a 2 h submaximal ride followed by a high intensity time trial task lasting approx. 35 min with each of 0, 20, 39 and 64 g·h-1 CHO ingestion rates during submaximal exercise. Each trial involved pre and post exercise assessments (MVC, Mwave twitch potentiation and force, motor unit recruitment and firing rate assessment using high density EMG) and during exercise (gross EMG amplitude). MVC peak torque values were reduced post exercise by -20.4 nM (95%CI: -26.5 to -14.4) in comparison to pre value on all trials with no differences between trials. The firing rates of early recruited motor units significantly increased by 1.55 pps (95%CI: 0.51 to 2.59) following exercise in comparison to pre-exercise rates. Gross EMG during the 2 h cycling bout revealed a main effect of treatment (p<0.01) but post hoc comparisons provided no clarity and likely reflect methodological issues. Consuming CHO at ingestion rates between 20 and 64 g·h-1 had little to no impact on the neuromuscular function of well-trained cyclists when comparing pre and post fatiguing exercise values. Despite differences in time trial completion time between trials, following exercise to fatigue in an endurance task, no post exercise differences were detected.

O gene TrSNF1, homólogo aos membros da subfamília das proteínas serina-treonina quinases ativadas por AMP (AMPK) e relacionadas a SNF1, foi isolado do fungo filamentoso trichoderma reesei. A seqüência de aminoácidos putativa possui um domínio de quinase com 42% de identidade e 59% de similaridade com outras proteínas quinases da mesma subfamília. Em S. cerevisiae a SNFl é essencial para a expressão de genes reprimidos por glicose, em resposta a privação de glicose do meio de cultura. A expressão de TrSNFl em levedura mutante para SNF1, restaura a função de SNF1. A expressão de um antisense de TrSNFl em T. reesei causa um atraso na expressão do gene regulado por glicose, CBHI. Além disso, em experimento utilizando matrizes de DNA foi possível observar uma alteração da tendência global da expressão gênica entre a cepa selvagem e a cepa antisense. A observação da homologia estrutural com proteínas quinase da mesma subfamília, a similaridade funcional com SNFl de S. cerevisiae, e a alteração no padrão da expressão gênica in vivo, sugerem que TrSNFl pode estar envolvido na regulação do metabolismo de carboidratos em T. reesei. / A gene homologue to the members of the AMP-activated/SNFl protein kinase subfamily, TrSNF1, was isolated from the filamentous fungus Trichoderma reesei. The predicted protein of 692 amino acids has a kinase domain, that share 42 % identity and 59 % similarity to that of serine/threonine protein kinase of this family. In Saccharomyces cerevisiae, the SNFl protein kinase is required for expression of glucose repressed genes in response to withdrawal of glucose from the medium. Expression of the Trichoderma reesei SNF1-related sequence in yeast SNFl mutant restores SNFl function. The TrSNFl antisense expression in T. reesei causes a control alteration in the glucose-regulated gene CBHI. The observed structural identity with the AMP-activated/SNFl protein kinase subfamily, and the functional similarity to the yeast SNFl suggest that the TrSNFl may be involved in the regulation of sugar metabolism in Trichoderma reesei.

A banana é um fruto climatérico que apresenta alta taxa respiratória e alta produção de etileno após a colheita, o que a torna altamente perecível. Acredita-se que o 1-MCP é capaz de ligar-se ao receptor do hormônio etileno, bloqueando sua ação e, consequentemente, retardando o amadurecimento do fruto. Bananas (Musa acuminata AAA cv. Nanicão) com aproximadamente 110 dias pós-antese foram armazenadas em condições controladas de umidade e temperatura. Parte da amostra foi tratada com 1-MCP (100 nl/L), outra parte foi tratada com etileno (100 ppm - 7L/min), e, uma terceira parte, foi mantida como controle. Os frutos foram caracterizados, durante o período de amadurecimento, em relação à produção de etileno e CO2 (por cromatografia à gás), à concentração de amido (pelo método enzimático descrito por Cordenunsi e Lajolo 1995) e açúcares (glicose, frutose, sacarose e maltose - por HPLC-PAD). Também foram analisados os comportamentos das enzimas &#945; e &#946;- amilases, fosforilase, DPE 1 e DPE 2 por atividade enzimática in vitro ou por P.A.G.E. nativo e, quando possível, foram avaliados os comportamentos destas enzimas frente a tradução (Western blotting) e transcrição proteica (Northern blotting). A degradação de amido, assim como a respiração, a produção de etileno e síntese de açúcares foram retardadas nos frutos tratados com o 1-MCP. Como consequência destas mudanças, também houve uma alteração nos perfis das atividades enzimáticas. Os resultados indicaram que o 1-MCP, além de atrasar o climatério respiratório, foi capaz de provocar descompasso no padrão de degradação de amido e síntese de açúcares sugerindo também que outros fatores temporais, necessários ao processo, foram prejudicados. Dentre as enzimas envolvidas no metabolismo de carboidratos de bananas, as &#945;-amilases não demonstraram ser etileno-dependentes (?) as &#946;-amilases mostraram ser enzimas bastante dependentes do etileno e parecem ter importância especial quando se trata do metabolismo da maltose, em conjunto com a DPE 2; atividade fosforolítica foi induzida ao longo do amadurecimento, mas parece ter resposta mais significativa a alterações basais do hormônio etileno e, portanto, sugere-se que esta enzima esteja envolvida com mais de uma forma de regulação; a DPE 1 apresentou maior atividade ao início da degradação do amido, indicando sua atuação sobre glicanos liberados pelas &#945;-amilases. A presença de DPEs na banana torna o seu metabolismo de carboidratos mais próximo daquele presente em folhas. / Banana is a climateric fruit that has a high respiration rate and a high ethylene production after harvest, what makes this fruit very perishable. It is believe that 1- MCP is capable to interact with the hormone ethylene receptors, blocking its action and, as result, delaying the fruit ripening. Bananas (Musa acuminata AAA cv. Nanicão) with 110 days after anthesis were stored in controlled conditions of umidity and temperature. Part of the sample was treated with 1-MCP (100 nl/L), another part was treated with ethylene (100 ppm - 7L1min), and, a third part, was kept as control.The fruits were characterized, along the ripening process, based on the ethylene and CO2 production (by gas chromatography), the starch amount (enzymatic method described by Cordenunsi and Lajolo, 1995) and sugars content (glucose, fructose, sucrose and maltose - by HPLC-PAD). Enzymes behaviors were also followed &#945; and &#946;-amylases, phosphorylase, DPE 1 and DPE 2 by enzymatic activity (in vitro ar native P.A.G .E.) and, when it was possible, the translation (Western blotting) and protein transcription (Northern blotting) were also analyzed. The starch degradation, as well as the CO2 and ethylene production and sugars synthesis were delayed in the fruits treated with the 1-MCP. As consequence of these changes, we also had an alteration in the enzymatic activity profiles. The results indicated that the 1-MCP, besides delaying the respiratory climateric, was capable to change the standard profile of starch degradation and synthesis of sugars, suggesting that other factors, necessary to the process, were damaged. Considering the involved enzymes in the carbohydrates metabolism of bananas, the &#945;-amylases did not demonstrated to be ethylene-dependents (?) &#946;-amylases seem to be ethylene-dependent and seem to have special importance in the maltose metabolism, working on it with the DPE 2; phosphorolytic activity was induced along the ripening, but it seems to have more significant relation to the basal alterations of the hormone ethylene, therefore, it suggests that this enzyme is involved with more than one type of regulation; DPE 1 presented greater activity in the beginning of the starch degradation, indicating its performance on glucans released by the &#945;-amylases activity. The presence of DPEs in bananas approximates its metabolism of carbohydrates to the leaves metabolism.

Lok Cheuk-ming, Andy. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 62-73). / Text in English; abstracts in English and Chinese. / Lok Cheuk-ming, Andy. / Acknowledgments --- p.i / Abstract --- p.iii / Table of Contents --- p.vi / List of Tables --- p.viii / List of Figures --- p.ix / Chapter CHAPTER1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Purpose --- p.4 / Chapter 1.3 --- Significance of Study --- p.4 / Chapter CHAPTER2 --- Review of Literature --- p.5 / Chapter 2.1 --- "Energy Metabolism During Prolonged, Submaximal Exercise" --- p.5 / Chapter 2.1.1 --- Energy Metabolism in Humans / Chapter 2.1.2 --- Amount of Energy Stores in Body / Chapter 2.1.3 --- Substrates Utilization during Prolonged Exercise / Chapter 2.2 --- Importance of Pre-exercise Nutrition on Exercise Performance --- p.9 / Chapter 2.2.1 --- Pre-exercise CHO Supplementation / Chapter 2.2.2 --- Timing of CHO and Transient Hypoglycemia / Chapter 2.2.3 --- Type of CHO / Chapter 2.2.4 --- Other Nutrients / Chapter 2.3 --- Application of the Glycemic Index to Pre-exercise Nutrition --- p.14 / Chapter 2.3.1 --- Definition of Glycemic Index (GI) / Chapter 2.3.2 --- Ingestion of GI Foods Before Exercise / Chapter 2.3.3 --- Summary of the Previous Findings / Chapter CHAPTER3 --- Methodology --- p.23 / Chapter 3.1 --- General Methods --- p.23 / Chapter 3.2 --- Participants --- p.34 / Chapter 3.3 --- Experimental Design --- p.34 / Chapter 3.4 --- Procedures --- p.37 / Chapter 3.5 --- Prescribed Glycemic Index Meals --- p.39 / Chapter 3.6 --- Analysis --- p.40 / Chapter 3.7 --- Statistical Analysis --- p.41 / Chapter CHAPTER4 --- Results --- p.42 / Chapter 4.1 --- Running Performance --- p.42 / Chapter 4.2 --- Dietary Analysis --- p.43 / Chapter 4.3 --- Physiological Changes At Rest and During Exercise --- p.44 / Chapter 4.5 --- Changes in Perceptual Variables and Heart Rates At Rest and During Exercise --- p.54 / Chapter CHAPTER5 --- Discussion --- p.56 / Recommendation and Applications --- p.61 / References --- p.62 / Appendices --- p.74

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Empresa Brasileira de Pesquisa AgropecuÃria / Os efeitos dos regimes irrigado e de sequeiro foram avaliados em folhas sombreadas e a pleno sol nos clones de cajueiro anÃo precoce (Anacardium occidentale L) CCP 76 e BRS 189. Os experimentos foram conduzidos na EstaÃÃo Experimental da Embrapa AgroindÃstria Tropical, em Paraipaba, CearÃ, entre setembro de 2006 e agosto de 2007. Mensalmente, foram investigados a condutÃncia estomÃtica, a taxa transpiratÃria, a taxa fotossintÃtica, a relaÃÃo entre a concentraÃÃo interna e externa de CO2, o potencial osmÃtico. O teor de Ãgua, de proteÃnas solÃveis, de prolina, de N-aminossolÃveis, de carboidratos (aÃÃcares totais, redutores e nÃo redutores e de amido), a atividade das enzimas do metabolismo do carbono, sintase da sacarose fostato (SPS), sintase da sacarose (SuSy), pirofosforilase do ADP glicose (AGPase) e das amilases (alfa, beta e total) foram determinados nas folhas das plantas bi-mensalmente.AlÃm disso, foram analisadas a qualidade pÃs-colheita dos pedÃnculos dos clones em ambos os tratamentos. Em geral, nÃo foram encontradas diferenÃas significativas entre os dois tipos de cultivos para os dois clones e tipos de folha em relaÃÃo aos parÃmetros fisiolÃgicos, tais como, fotossÃntese, transpiraÃÃo e condutÃncia estomÃtica. Essas variÃveis foram afetadas apenas em funÃÃo da Ãpoca do ano. Carboidratos, tais como amido e aÃÃcares redutores, tiveram uma tendÃncia de acÃmulo nas folhas de sol e de sombra no mÃs de maio, exibindo teores menores no mÃs de setembro, Ãpoca em que os teores de aÃÃcares nÃo-redutores (sacarose) aumentaram para suprir a formaÃÃo de frutos. Sob o regime nÃo irrigado, as enzimas SPS, SuSy e AGPase tiveram suas atividades justificadas parcialmente quando relacionadas com as variaÃÃes nos teores de aÃÃcares totais e amido. A atividade amilÃsica total variou para os regimes de irrigaÃÃo, clone e folhas em relaÃÃo ao perÃodo do ano. A supressÃo da irrigaÃÃo para os clones CCP 76 e BRS 189 durante o experimento nÃo foi capaz de modificar a qualidade pÃs-colheita dos pedÃnculos de caju. As variaÃÃes ao longo do experimento comprovam o efeito da forÃa dos drenos nas diversas fases fenolÃgicas e para os ÃrgÃos reprodutivos das plantas de cajueiro. As plantas de cajueiro anÃo precoce possuem, portanto, uma plasticidade, quando cultivadas em condiÃÃes de sequeiro, conseguindo manter suas atividades metabÃlica e fisiolÃgica vitais sem maiores danos à planta como um todo. / Effects of irrigation and drought regimen were evaluated on shaded and sunny leaves in clones of early dwarf cashew trees (Anacardium occidentale L) CCP 76 and BRS 189. The experiments were conducted at the Embrapa Agro indÃstria Tropical experimental station in Paraipaba, CearÃ, between Setember of 2006 and August of 2007. The means for the obtained data were statistically analysed at a 5% level of significance. Stomatal conductance(gs), respiratory rate(E), photosynthetic rate (A), relation between inner and outer concentration of CO2 (Ci/Car), osmotic potential (&#936;s) and water usage efficiency were accessed monthly. The relative water cont ent, of soluble proteins, prolin, N-amino soluble, of sugars (soluble, reductants, non- reductants, starch) and activity of carbon metabolism enzymes, sucrose-phosphate synt hase (SPS), sucrose synthase (SuSy), ADP phosphorylase, glucose and amylases (alfa, beta and total) were determined on leaves each two months. Beyond that, the postharvest qual ity of pseudofruits of the clones on both treatments was accessed. In general, no significant differences were found among cultivations for both clones in relation to physiological parameters, like photosynthesis, transpiration and stomatal conductance. These variants were affected only in function of the time of year. Independently of irrigation regimen, wate r usage efficiency was lower during the drought (from June to December) in relation to the months with higher pluviometric precipitation (from January to May). Carbohydr ates such as starch and reductant sugars tend to accumulate on both sunny and shaded leaves on May, while their contents are smaller on September, a time when non-reductant sugars (sucrose) increase in order to supply fruit formation. Under a drought regimen, enzymes SPS, SuSy and ADP correlate partially with the variations of contents of soluble sugars and starch. Total amylasic activity varied for irrigation regimens, clones and kind of leaves in relation to the period of the year. The supression of the hydric regimen for the clones CCP 76 and BRS 189 during the experiment wasn't able to chan ge the postharvest quality of the cashew pseudofruits. The variations shown during the experiment confirm the effect of drainage strength on several phenological phases and for the reprodutive or gans of the cashew trees. The trees of early dwarf cashew have, therefore, some plasticity when exposed to drought conditions, being able to maintain metaboli cal and physiological activity without major damage to the individual as a whole.

There is increasing interest in special heptose carbohydrates, their multifunctional roles from a plant physiological view point in fruit growth and development as well as in the whole plant in general due to their potential in mitigating photo-oxidative injury to the whole plant system and the image of avocado as ‘health fruit’. Studies have been carried out to investigate the role of avocado heptoses, rare carbohydrates predominantly produced in avocado. Several authors have documented various research findings and speculated on multifunctional roles of avocado special sugars. However, few reports have made an attempt to elucidate the multifunctional roles of avocado heptose carbohydrates as: ‘sources of energy’, storage and phloem-mobile transport sugars, and precursors for formation of antioxidants. Assessing the avocado carbohydrates over the plant growth and development during ontogeny may, therefore, offer clues to better understand whole plant behaviour. Plant sampling was carried out over different developmental stages. Using plants grown in the light versus etiolated seedlings; sugar determinations were also done to determine what sugar is produced from which storage organs. The sugars were extracted and analysed by isocratic HPLC/RID. The embryo had 47.11 % hexose and 52.96 % heptose sugars. The seed, however, also released significant amounts of D-mannoheptulose (7.09 ± 1.44 mg g-1 d. wt) and perseitol (5.36 ± 0.61 mg g-1 d. wt). Similarly fruit and leaf tissues had significant amounts of heptoses relative to hexoses at specific phenological stages. In postharvest ‘readyto-eat’ fruit the following carbohydrate concentrations were as follows:exocarp heptoses 13 ± 0.8; hexoses 4.37 ± 1.6 mg g-1 d. wt, mesocarp heptoses 8 ± 0.2; hexoses 3.55 ± 0.12 mg g-1 d. wt), seed heptoses (only perseitol) 13 ± 1.1; hexoses 5.79 ± 0.53 mg g-1 d. wt. The results of this experiment was the first to demonstrate that the heptoses D-mannoheptulose, and its polyol form, perseitol, are found in all tissues/organs at various phenological stages of avocado growth and development. Secondly, heptoses, as well as starch are carbohydrate reserves that are found in avocado. The heptoses, beyond being abundantly produced in the avocado plant, are also found in phloem and xylem saps as mobile sugars. The study also presents data on the interconversion of the C7 sugars Dmannoheptulose and perseitol. It is deduced that D-mannoheptulose can be reduced to perseitol, and perseitol can also be oxidized to D-mannoheptulose by enzymes present in a protein extract of the mesocarp. The potential catalyzing enzyme is proposed to be an aldolase, as electrophoretic determinations prove the presence of such an enzyme during various stages of development in various plant organs. Avocado heptoses play an important role in plant growth and development and in fruit in particular. Moreover, they are reported as sources of anti-oxidants, and contribute significantly to fruit physiology if they function in coordination with other anti-oxidants in fruit tissues. To evaluate the presence of anti-oxidant systems throughout avocado fruit development, various tissues were analysed for their total and specific anti-oxidant compositions. Total anti-oxidant levels were found to be higher in the exocarp and in seed tissue than in the mesocarp. While seed tissues contained predominantly ascorbic acid (AsA) and total phenolics (TP), the anti-oxidant composition of the mesocarp was characterised by the C7 sugar, D-mannoheptulose. Among the anti-oxidant enzymes assayed, peroxidase (POX) and catalase (CAT) were present in higher concentrations than superoxide dismutase (SOD) in mesocarp tissue. Different anti-oxidant systems seem to be dominant within the various fruit tissues. Carbohydrates are the universal source of carbon for cell metabolism and provide the precursors for the biosynthesis of secondary metabolites, for example via the shikimic acid pathway for phenols. The preharvest free and membrane-bound phenols, catechin and epicatechin, are distributed differently in the various fruit tissues. Membrane-bound and free phenols also play a role as anti-oxidants, with free ones being more important. KSil (potassium silicate) application to fruit as postharvest treatment was used to facilitate the release of conjugates to free phenols via lysis. This treatment improved fruit shelf life. Western blotting also revealed that postharvest Si treatment affects the expression of enzymatic anti-oxidant-catalase (CAT). Overall the thesis results revealed that C7 sugars have anti-oxidant properties and that D-mannoheptulose is the important anti-oxidant in the edible portion of the avocado fruit. Dmannoheptulose is furthermore of paramount importance as a transport sugar. Perseitol on the other hand acts as the storage product of D-mannoheptulose, which can be easily converted into D-mannoheptulose. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Despite numerous attempts involving a variety of target genes, the successful transgenic manipulation of sucrose accumulation in sugarcane remains elusive. It is becoming increasingly apparent that enhancing sucrose storage in the culm by molecular means may depend on the modification of the activity of a novel gene target. One possible approach to identify target genes playing crucial coarse regulatory roles in sucrose accumulation is to assess gene expression during the developmental transition of the culm from active growth to maturation. This study has resulted in the successful optimisation of a mRNA hybridisation technique to characterise the expression of 90 carbohydrate metabolism-related genes in three developmentally distinct regions of sugarcane culm. A further goal of this work was to extend the limited knowledge of the regulation of sucrose metabolism in sugarcane, as well as to complement existing data from physiological and biochemical studies. Three mRNA populations derived from the different culm regions were assayed and their hybridisation intensities to the immobilised gene sequences statistically evaluated. The relative mRNA transcript abundance of 74 genes from three differing regions of culm maturity was documented. Genes exhibiting high relative expression in the culm included aldolase, hexokinase, cellulase, alcohol dehydrogenase and soluble acid invertase. Several genes (15) were demonstrated to have significantly different expression levels in the culm regions assessed. These included UDP-glucose pyrophosphorylase and UDP-glucose dehydrogenase, which were down-regulated between immature and mature internodes. Conversely, sucrose phosphate synthase, sucrose synthase and neutral invertase exhibited up-regulation in maturing internodal tissue. A variety of sugar transporters were also found to be up-regulated in mature culm, indicating a possible control point of flux into mature stem sink tissues. Combined with knowledge of the levels of key metabolites and metabolic intermediates this gene expression data will contribute to identifying key control points of sucrose accumulation in sugarcane and assist in the identification of gene targets for future manipulation by transgenic approaches. / AFRIKAANSE OPSOMMING: Ondanks verskeie pogings, waartydens verskeie gene geteiken is, is daar nog weinig sukses behaal om sukrose-akkumulering te verhoog. Toenemend wil dit voorkom asof suksesvolle genetiese manipulering van sukroseberging in die stingel van die verandering van ‘n nuwe geen afhanklik sal wees. Een van die moontlike benaderings wat gevolg kan word om potensiële teiken gene wat ‘n belangrike rol in die beheer van sukrose-opberging speel te identifiseer, is om geen uitdrukkingspatrone in die stingel tydens die omskakeling van aktiewe groei tot volwassenheid te karakteriseer. In hierdie studie is ‘n metode gebaseer op die hibridisering van mRNA geoptimiseer en suksesvol aangewend om die uitdrukkingspatrone van 90 verskillende geselekteerde gene, wat vir sleutelensieme in die beheer van koolhidraatmetabolisme kodeer, te bestudeer. Die doel met die ondersoek was om die beperkte kennis oor die regulering van koolhidraatmetabolisme uit te brei en om die bestaande inligting afgelei van fisiologiese en biochemiese-studies aan te vul. Drie verskillende mRNApopulasies, verkry uit verskillende dele van die stingel, is ontleed deur verskillende peilers te gebruik. Die gegewens is statisties ontleed en dit het afleidings oor die verandering in uitdrukking van hierdie gene moontlik gemaak. Die relatiewe konsentrasies van 74 verskillende gene is gedokumenteer. Gene wat sterk uitgedruk word het aldolase, heksokinase, sellulase, alkoholdehidrogenase en ongebonde suurinvertase ingesluit. Die uitdrukkingspatrone van 15 gene het tussen die verkillende weefsels gevarieer. Gene waarvan die uitdrukking tydens die oorgang na volwassenheid verlaag sluit in UDP-glukose pirofosforilase en UDP-glukose dehidrogenase en waarvan die uitdrukking verhoog sukrosefosfaatsintase, sukrosesintase en neutrale invertase in. Die uitdrukking van verskeie suikertransporter gene verhoog tydens volwassewording. Hierdie inligting te same met die huidige kennis oor heersende metabolietvlakke sal bydrae tot die identifisering van geenteikens vir toekomstige genetiese manupulering.

O gene TrSNF1, homólogo aos membros da subfamília das proteínas serina-treonina quinases ativadas por AMP (AMPK) e relacionadas a SNF1, foi isolado do fungo filamentoso trichoderma reesei. A seqüência de aminoácidos putativa possui um domínio de quinase com 42% de identidade e 59% de similaridade com outras proteínas quinases da mesma subfamília. Em S. cerevisiae a SNFl é essencial para a expressão de genes reprimidos por glicose, em resposta a privação de glicose do meio de cultura. A expressão de TrSNFl em levedura mutante para SNF1, restaura a função de SNF1. A expressão de um antisense de TrSNFl em T. reesei causa um atraso na expressão do gene regulado por glicose, CBHI. Além disso, em experimento utilizando matrizes de DNA foi possível observar uma alteração da tendência global da expressão gênica entre a cepa selvagem e a cepa antisense. A observação da homologia estrutural com proteínas quinase da mesma subfamília, a similaridade funcional com SNFl de S. cerevisiae, e a alteração no padrão da expressão gênica in vivo, sugerem que TrSNFl pode estar envolvido na regulação do metabolismo de carboidratos em T. reesei. / A gene homologue to the members of the AMP-activated/SNFl protein kinase subfamily, TrSNF1, was isolated from the filamentous fungus Trichoderma reesei. The predicted protein of 692 amino acids has a kinase domain, that share 42 % identity and 59 % similarity to that of serine/threonine protein kinase of this family. In Saccharomyces cerevisiae, the SNFl protein kinase is required for expression of glucose repressed genes in response to withdrawal of glucose from the medium. Expression of the Trichoderma reesei SNF1-related sequence in yeast SNFl mutant restores SNFl function. The TrSNFl antisense expression in T. reesei causes a control alteration in the glucose-regulated gene CBHI. The observed structural identity with the AMP-activated/SNFl protein kinase subfamily, and the functional similarity to the yeast SNFl suggest that the TrSNFl may be involved in the regulation of sugar metabolism in Trichoderma reesei.