Le débourrement des bourgeons axillaires conditionne la ramification, donc l’établissement de l’architecture chez les végétaux. L’azote est impliqué dans la croissance des jeunes organes tels que les axes secondaires (axes II) issus du débourrement des bourgeons. Plusieurs études ont démontré que la concentration en acides aminés augmente dans la sève au cours de la reprise de croissance printanière, dont le débourrement des bourgeons est une étape importante. L’identité et l’origine des acides aminés impliqués dans le débourrement et les premières phases d’allongement des axes II n’ont pourtant pas encore été clairement établies. Ce travail a pour objectif de comprendre, chez Rosa hybrida, les phénomènes nutritionnels sous-jacents à l’apparition de différents phénotypes de ramification. Pour ce faire, nous avons fait varier la concentration et les périodes d’apport de nitrate dans la solution nutritive au cours de la croissance, avant et après l’initiation du débourrement par décapitation. Nous avons montré in planta que la concentration d’asparagine augmente dans la sève et dans l’ensemble des tissus pendant l’allongement des axes II et provient tout d’abord majoritairement des réserves puis, après la décapitation, en quantité de plus en plus importante de l’absorption courante. Cet acide aminé est le seul capable, en présence de sucres, d’initier une croissance efficace des axes II in vitro, notamment en contribuant à placer le statut des régulateurs de croissance dans un contexte favorable au débourrement. Une approche par RNAseq a mis en évidence 848 séquences potentiellement impliquées dans le débourrement en réponse au nitrate. Parmi elles, le couple Asparaginase / Asparagine synthétase s’exprime respectivement durant la phase de dormance ou le débourrement, ce qui renforce l’importante de l’asparagine dans ce phénomène. Ces deux échelles d’approche ont permis de compléter le modèle intégratif du débourrement en intégrant la nutrition des nouveaux organes. / Axillary bud outgrowth is an essential process of plant branching to set-up its architecture. Nitrogen is implicated in the development of young organs such as secondary axes (axes II) resulting from bud outgrowth. Several studies have previously shown that amino acid concentration increase in the xylem sap during spring regrowth whom bud outgrowth is an essential step. The exact nature of the amino acids implicated in the bud outgrowth and initial axe II elongation have not yet been determinated. The present work aims to understand in Rosa hybrida the nutrition processes implicated in the set-up of different branching phenotypes. To achieve this goal, we brought different nitrate concentrations to the plant before and after bud outgrowth initation by apex removing. We showed in planta that asparagine concentration increases in the sap and in the tissues during axes II growth, initialy originating from internal stores and, after decapitation, increasingly coming from current uptake. This amino acid is the sole able to evoke in vitro an efficient elongation of axes II in the presence of sugar throught the establishment of growth regulators metabolism status that is favorable to the outgrowth process. Transcriptome study using RNAseq features 848 sequences that are potentially implicated in bud outgrowth in response to nitrate. Among them, the expression of Asparaginase takes place during dormancy while, in contrast, Asparagine synthase gene is active during bud outgrowth, highlighting the importance of asparagine in this phenomenon. These approaches conducted at two different scales contribute to append with nitrogen nutrition the integrated model of bud outgrowth.

The role of sugars as regulatory signals has mainly focused on their effects on plant growth, development, gene expression, and metabolism. Little, however, is known about their role in controlling secondary metabolism. Previous work in our lab showed that sugars affect the production of the sesquiterpene antimalarial drug, artemisinin, in hairy roots of Artemisia annua. In this study, sugars alone or in combination with their analogues were used to investigate if sugars control artemisinin production in Artemisia annua seedlings. Compared to sucrose, a 200% increase in artemisinin by glucose was observed. When the glucose analog, 3-O-methylglucose, which is not phosphorylated effectively by hexokinase, was added with glucose, artemisinin production was dramatically decreased but hexokinase activity was significantly increased compared to glucose. In contrast, neither mannose, which can be phosphorylated by hexokinase, nor mannitol, which can not be transported into cells had any significant effect on artemisinin yield. When different ratios of fructose to glucose were added to seedlings, artemisinin yield was directly proportional to glucose concentration. Although addition of sucrose with glucose gave inconclusive results, sucrose analogues decreased artemisinin production compared to sucrose. These results suggested that both monosaccharide and disaccharide sugars may be acting as signal molecules thereby affecting the downstream production of artemisinin. Taken together, these experiments showed that sugars clearly affect terpenoid production, but that the mechanism of their effects appears to be complex.

No description available.

No description available.

Arrhythmias are often caused by aberrant ion channel activity, resulting in remodeling of the cardiac action potential. Two K + currents, IKs and IKr, contribute to phase III repolarization of the human cardiac action potential. Human ether-a-go-go-related gene 1 (hERG1), a voltage-gated potassium channel, underlies IKr. Alterations in the repolarization phase of the action potential, and in particular IKr, can lead to arrhythmias, long or short QT syndrome, heart disease, and sudden cardiac death. HERG1A has two putative N-glycosylation sites located in the S5-S6 linker region, one of which is N-glycosylated. The aim of the first study was to determine whether and how N-linked glycosylation modifies hERG1A channel function. Voltage-dependent gating and kinetics of hERG1A were evaluated under conditions of full glycosylation, no sialylation, in the absence of complex N-glycans, and following the removal of the full N-glycosylation structure. The hERG1A steady state activation relationship was shifted linearly along the voltage axis by a depolarizing ~9 mV under each condition of reduced glycosylation. Steady state channel availability curves were shifted by a much greater depolarizing 20–30 mV under conditions of reduced glycosylation. There was no significant difference in steady state gating parameters among the less glycosylated channels, suggesting that channel sialic acids are responsible for most of the effect of N-glycans on hERG1A gating. A large rightward shift in hERG1A window current for the less glycosylated channels was caused by the observed depolarizing shifts in steady state activation and inactivation. The much larger shift in inactivation compared to activation leads to an increase in hERG1A window current. Together, these data suggest that there is an increase in the persistent hERG current that occurs at more depolarized potentials under conditions of reduced glycosylation. This would lead to increased hERG1A activity during the AP, effectively increasing the rate of repolarization, and reducing AP duration, as observed through in silico modeling of the ventricular AP. The data describe a novel mechanism by which hERG1A activity is modulated by physiological and pathological changes in hERG1A glycosylation, with increased channel sialylation causing a loss of hERG1A activity that would likely cause an extension of the ventricular AP. The second study was to evaluate possible changes in antibiotic drug block as a result of alterations to N-glycosylation. We determined that N-glycans play a protective role on the hERG1A channel. SMX, Erythromycin, and Penicillin G were assessed individually at three concentrations. The data showed increases in antibiotic block with decreases in N-glycans. In addition, alterations in the voltage-dependence of block with changes in N-glycans were observed. SMX block was voltage-independent at each drug concentration under conditions of reduced sialylation only. Overall, these data indicate a functional role for N-glycosylation in the modulation of hERG1A antibiotic block, suggesting that even small changes in channel N-glycosylation modulate hERG1A block, and thereby likely impact the rate of action potential repolarization. The data from these studies enhances our understanding of the role of N-glycosylation on hERG1A function and drug block, and how that role will impact the cardiac action potential and overall cardiac excitability.

A mid-infrared chalcogenide fiber optic probe was employed to develop a Fourier transform infrared spectroscopy-based partial-least-squares (PLS) calibration model for the quantitative analysis of sucrose, glucose, fructose, maltose, total sugar and water content in chocolate syrup. Based on the comparison of the pure component and correlation spectra extracted from chocolate syrup and aqueous sugar solutions based models, it was determined that the tightness of the concentration ranges and the ratios of the sugars in the chocolate syrup samples did not allow to draw adequate information to build a robust PLS calibration model. PLS regression models developed using infrared spectra of chocolate syrup calibration standards prepared by addition of sugar solutions to increase the concentration range did not yield conclusive results. A different approach used for standard preparation consisted of diluting chocolate syrup samples to different degrees. This new method provided an increased concentration range for the sugars but maintained an almost constant sugar to sugar ratios. The PLS models based on these new calibration standards yielded high calibration correlation coefficients and low errors on the external validation. Accuracy, repeatability, long-term stability and ruggedness were tested and the results demonstrated that the calibration models were robust and had a better repeatability than the reference high-performance liquid chromatography method. The fact that the calibration model was developed using standards having very similar sugar profiles precluded its use for the analysis of chocolate syrup samples of different formulations. The resulting formulation-specific PLS regression model required a preclassification step to ensure that the model is applied to the appropriate sample type. A probabilistic neural network (PNN) model was developed to fulfill the preclassification requirement. PNN yielded excellent classification results. The modeling uncovered

No description available.

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 104-124). Also available on the World Wide Web.

AN ABSTRACT OF THE THESIS OF Thara G. Siddaramu, for the Master of Science degree in Civil and Environmental Engineering, presented on February 5, 2011, at Southern Illinois University Carbondale. TITLE: EVALUATION OF DIFFERENT PRETREATMENT APPROACHES FOR DISRUPTING LIGNOCELLULOSIC STRUCTURES MAJOR PROFESSOR: Dr. Yanna Liang There are two major steps in biofuel production- pretreatment of lignocellulosic materials and enzymatic hydrolysis. The present study investigated the ability of two pretreatment methods, namely traditional oven and microwave oven treatments for disrupting lignocellulosic structures. The substrates tested were Jatropha seed cake and sweet sorghum bagasse. In recent years, Jatropha curcas also known as physic nut or purging nut has attracted extensive attention due to its several unique characteristics. Similarly, sweet sorghum has the potential to provide great value to energy sectors and food industries being that the entire plant is rich in various sugars and nutrients. Both crops can adapt to various climates, and can withstand extended drought conditions compared to other crops. Additionally, both Jatropha seed cakes and sweet sorghum bagasse are good sources of lignin and carbohydrates, which could be used for production of biofuels only if the sugars can be unlocked. Several treatment methods such as mechanical, physical, chemical and biological treatments have been reported to breakdown the cellulosic structure of biomass. However, other low cost and quicker methods, such as ovenpretreatment and microwave irradiation have not been evaluated for Jatropha seed cake and Sweet Sorghum Bagasse (SSB), respectively. Composition change of Jatropha seed cake samples was evaluated upon lime pretreatment at 100 oC with different parameters. With a lime dose of 0.2 g and a water content of 10 ml per gram of cake and a treatment period of 1 h, 38.2 ± 0.6% of lignin was removed. However, 65 ± 16% of hemicellulose was also lost under this condition. For all the treatments tested, cellulose content was not affected by lime supplementation. Through further examining total reducing sugar (TRS) release by enzymatic hydrolysis after lime pretreatment, results indicated that 0.1 g of lime and 9 ml of water per gram of cake and 3 h pretreatment produced the maximal 68.9% conversion of cellulose. Without lime pretreatment, the highest cellulose conversion was 33.3%. Finally, this study shows that Jatropha seed cake samples could be hydrolyzed by enzymes. Even though the cellulose content was not high for this Jatropha cake sample, the fractionation by lime presented in this study opened the door for other applications, such as removal of lignin and toxicity for use as animal feed and fertilizer. The microwave radiation pretreatment of SSB was evaluated with or without lime (0.1 g/g bagasse) at 10 ml water/g bagasse for 4 min. TRS release over 72-h enzymatic hydrolysis was different for samples treated differently and at different solid loadings. The TRS concentration was increased by 2 and 5-fold from 0 to 24 hours in non lime-pretreated and lime-pretreated samples, respectively. Further incubation of samples for 48 and 72 h did not result in increased TRS. Comparing different solid loadings of samples treated with or without lime, 1% solid content resulted in 1.4 times higher TRS increase than that of 5% solid concentration. Therefore, lime was effective in disintegrating lignocellulosic structures and making cellulose more accessible for saccharification. Higher solid loadings which can lead to higher sugar concentrations are desired for downstream biofuel production. But, as shown in this study, higher concentration of bagasse samples decreased rate of cellulose hydrolysis due to poorer mixing efficiency and hindrance to interactions between enzymes and solid materials. Thus, an optimal solid content needs to be determined for maximal cellulose hydrolysis and for preparing the hydrolysates for downstream processes, either bioethanol or lipid production.