Characterisation of selected Arabidopsis aldehyde dehydrogenase genes: role in plant stress physiology and regulation of gene expression

The importance of aldehyde dehydrogenase (ALDH) proteins in plant stress responses was investigated in this study by functionally analysing transgenic Arabidospsis thaliana ALDH knock-out and over-expressing plants. From the nine ALDH gene families present in Arabidopsis, four gene members of the families 10, 3 and 7 have been analysed in this work. Both ALDH10A8 (AT1G74920) and ALDH10A9 (AT3G48170) belong to the family 10 of the superfamily of ALDH proteins and, based on sequence similarity, they putatively code for betaine aldehyde dehydrogenases (BADHs), enzymes that catalyse the last step of glycine betaine biosynthesis. But, Arabidopsis is known not to be able to produce glycine betaine. The function of these two genes was therefore investigated. ALDH10A8 was found to be localized in leucoplasts whereas ALDH10A9 is targeted to peroxisomes. The ALDH10A8 and ALDH10A9 transcripts were detected in the plant and were slightly induced by stress treatments. Plants lacking ALDH10A8 transcripts were found to be drought and salt sensitive, indicating that ALDH10A8 may be involved in other pathways than the biosynthesis of glycine betaine in Arabidopsis. Using betaine aldehyde, 4-aminobutyraldehyde (ABAL) and 3-aminopropionaldehyde (APAL) as substrates, the recombinant ALDH10A9 protein showed both betaine aldehyde and aminoaldehyde dehydrogenase activities, although the affinity to the substrates was low compared to data from the literature. No enzymatic data was obtained for ALDH10A8 as it was not possible to purify sufficient amounts of the enzyme in its active form. Considering the high amino acid sequence similarity between ALDH10A8 and ALDH10A9, I propose that ALDH10A8 may be also active in vivo and likely both proteins function as aminoaldehyde dehydrogenases by detoxifying cells from metabolism-derived cytotoxic aminoaldehydes. The Arabidopsis ALDH3H1 (AT1G44170) gene belongs to the family 3 of the ALDH superfamily. Previous findings showed that ALDH3H1 transcripts mostly accumulate in roots of 4 week-old plants upon ABA, dehydration and NaCl treatments. Here, the expression analysis was extended to the protein level and in adult plants. Together with the previous observations it is found that the up-regulation of ALDH3H1 protein by salt stress mainly occurs in leaves of plants older than 4 weeks. To understand the function of ALDH3H1 in the stress response of Arabidopsis, transgenic plants over-expressing the ALDH3H1 protein were generated and analysed. It appeared that the constitutive expression of ALDH3H1 did not confer stress tolerance to the transgenic plants. However, the results indicate that the ALDH3H1 protein can help the plant to cope with stress injuries by alleviating damages from lipid peroxidation. Besides, the results from this study gives for the first time the experimental evidence that the ALDH3H1 short transcript variant (AT1G44170.3 (T3)) is expressed in Arabidopsis. It is nearly absent or expressed at a very low level in the wild type but accumulates in the 3h1-A mutant, which carries a T-DNA insertion in the first exon of the ALDH3H1 locus. The expression of the transcript T3 is shown to be directed by an alternative promoter comprised within the first intron of this gene. T3 and other ALDH3H1 transcript variants (AT1G44170.1 (T1) and AT1G44170.2 (T2)) are found to be differentially expressed in roots and shoots. Sub-cellular localisation experiments indicated that the protein T3 is targeted to the cytosol but its presence could be revealed neither in the 3h1-A mutant nor the wild type by using ALDH3H1 antibodies. Comparative analysis of the wild type and different T-DNA insertion mutants showed that the transcript T3 does not functionally compensate the lack of T1 and T2 under salt stress. The possible origin and functions of the transcript T3 are discussed. It is hypothesized that aldehydes may function as signal molecules and trigger aldehyde dehydrogenase gene expression. To test this hypothesis, transgenic plants expressing the β-glucuronidase (GUS) reporter gene driven by the ALDH7B4 (AT1G54100) gene promoter were generated (7B4-GUS). The ALDH7B4 promoter was found to be constitutively active in naturally desiccation-tolerant organs like seeds and pollen. In addition, both pentanal and trans-2-hexenal activated the promoter. The comparison of the GUS activities revealed that dehydration and NaCl induce the promoter stronger than trans-2-hexenal. To further understand the mechanism of the promoter activation by aldehydes the enzymatic activity of the GUS protein in plant extracts was compared to the accumulation pattern of malondialdehyde (MDA). Except for the methyl viologen treatment, no correlation was found between the GUS activity and the plant MDA content for the other treatments. Moreover, the in silico analysis of the ALDH7B4 promoter region revealed the presence of several stress-related cis-elements including one putative dehydration-responsive element/C-repeat – low temperature-responsive element (DRE/CRT-box) and three ACGT-boxes. The functional analysis of these elements suggested that the two proximal ACGT2 and ACGT3 boxes are the most influential ACGT-boxes involved in the salt response of the promoter. To identify factors involved in the aldehyde-induced expression of ALDH genes, a genome-wide mutagenesis approach has been chosen. Seeds from a homozygous transgenic 7B4-GUS plant were treated by the mutagen ethyl methanesulphonate (EMS). A second generation seed population has been generated

Early topping: an alternative to standard topping increases yield in cannabis production

In commercial settings, cannabis is generally propagated through cuttings, a process referred in the industry as cloning. Some producers perform either topping or fimming to trigger the production of axillary shoots, which will enhance the number of flowers per plants and thus increase the yield of the cannabis plants. Topping or fimming is generally performed after the cuttings have been transferred to rooting media for two weeks. We have tested a new method to increase the shoot number per plant. The modification of the standard topping method consist of performing the topping on mother plants, prior to taking the cuttings for cloning, and the cuttings are taken one week after the topping is performed. The resulting plantlets develop axillary shoots much faster and the time of production from cuttings to harvesting is decreased by 7-10 days. The method proposed herein requires minimal adjustment to the existing workflow and the plants produce as much as when standard topping is performed. Moreover, this method cuts backs on the production time and nearly two weeks are saved compared to the standard topping procedure since the plantlets do not need to recover after topping. Application of this new procedure results in faster production time and ultimately enhanced productivity

Historicizing and fictionalizing yoruba deities as narrative strategies in Changó, el gran putas by Zapata Olivella

This study of Changó by Zapata Olivella shows a worldview, an ideology that is neither strictly Western nor strictly rational. Thus my interest in this work rests on the author's creative ability to devote Changó to changing conventions. In attempting to valuate négritude, the author re-appropriates this literary movement, purges it of the Manichaeism it adopted from the dialectic of European ideologies of hierarchy of thoughts which assert that European is analytical and Black pre-logical. Zapata Olivella thereby establishes a more nuanced and complex set of relationships in négritude. Set in this ideological framework, Changó is a model of négritude discourse which harmoniously blends indigénisme and negrismo in a historiographic metafictional intertextuality where orality, writing, history, politics, and anthropology come together in defiance of linear writing. As such, Changó is a discourse with social visions which does not overlook the dynamism of black political ideologies but takes into consideration the recombinant qualities of black Atlantic's affirmative, sociopolitical cultures

Gestion traditionnelle et statut des ressources génétiques du sorgho (Sorghum bicolor L. Moench) au Nord-Ouest du Bénin

Le sorgho, Sorghum bicolor (L.) Moench, est une importante ressource alimentaire au Bénin. Sa culture est essentiellement pratiquée au centre et au nord du pays. Afin de mieux comprendre le niveau de diversité et les systèmes traditionnels de gestion et de conservation des variétés locales cultivées au Nord-Ouest du pays, une enquête basée sur une approche participative de recherche a été conduite dans 13 villages régulièrement distribués dans la zone. Au total, 45 variétés locales (61 noms vernaculaires) ont été inventoriées, présageant d’une grande diversité génétique du sorgho dans le milieu. Le nombre moyen de variétés locales inventoriées est de cinq par village et de deux par ménage. La distribution des variétés à travers la zone d’étude a été déterminée et les principaux facteurs y afférant étudiés. La couleur des grains, la durée du cycle végétatif ou la valeur marchande sont les plus importants critères utilisés par les producteurs pour la dénomination, l’identification, la classification et la sélection des variétés. Les systèmes traditionnels de sélection et de gestion des semences varient substantiellement d’un village à un autre et d’une ethnie à l’autre. Aussi, l’étudea-t-elle révélé l’existence dans certains villages d’une menace de disparition des variétés à cycle végétatif long et à grains blancs. Des efforts concertés devraient donc être déployés pour la valorisation et la préservation des ressources génétiques de cette céréale afin d’accroître sa production pour une meilleure sécurité alimentaire au Bénin.Mots clés: Bénin, diversité variétale, conservation, Sorghum bicolo

Mise en place d'un Système d'Information Géographique pour l'amélioration de la desserte du réseau des transports urbains valentinois

Face à la complexification et à la multitude de données à la portée des acteurs du domaine des transports, la mise en œuvre d'un Système d'Information Géographique se révèle l'un des meilleurs moyens de maîtrise de l'information et d'aide à la décision. Ce mémoire aborde la mise en place du SIG du réseau des transports urbains valentinois, initié pour affiner la connaissance du marché et pour améliorer l'offre de desserte de l'agglomération. Il expose la démarche, la conception, le montage, l'architecture et l'organisation de l'interface, ainsi que les différentes étapes que requiert la mise en œuvre d'un SIG auprès d'un exploitant de transports. Quelles utilisations concrètes peut offrir cet outil ? Et pour quels coûts ? Après une évaluation des coûts de sa mise en œuvre, ce mémoire expose, à travers l'analyse de l'accessibilité du réseau, quelques exemples des nombreuses applications des SIG. À partir d'isochrones, le travail montre alors différents apports de ce type d'outil, par des analyses spatiales qui permettent des lectures de la couverture et de la performance du réseau. Comment se présente aujourd'hui le réseau valentinois par rapport à la localisation des différentes catégories de la population de l'agglomération ? Il évoque aussi les difficultés rencontrées, les échecs et les possibilités d'extension du SIG. Enfin, il tente de suggérer des solutions et une amélioration du réseau et de sa structure actuelle.SIG, données, desserte, îlots, couverture, accessibilité, hiérarchisation

Aldehyde Dehydrogenases in Arabidopsis thaliana: Biochemical Requirements, Metabolic Pathways, and Functional Analysis

Aldehyde dehydrogenases (ALDHs) are a family of enzymes which catalyze the oxidation of reactive aldehydes to their corresponding carboxylic acids. Here we summarize molecular genetic and biochemical analyses of selected Arabidopsis ALDH genes. Aldehyde molecules are very reactive and are involved in many metabolic processes but when they accumulate in excess they become toxic. Thus activity of aldehyde dehydrogenases is important in regulating the homeostasis of aldehydes. Overexpression of some ALDH genes demonstrated an improved abiotic stress tolerance. Despite the fact that several reports are available describing a role for specific ALDHs, their precise physiological roles are often still unclear. Therefore a number of genetic and biochemical tools have been generated to address the function with an emphasis on stress-related ALDHs. ALDHs exert their functions in different cellular compartments and often in a developmental and tissue specific manner. To investigate substrate specificity, catalytic efficiencies have been determined using a range of substrates varying in carbon chain length and degree of carbon oxidation. Mutational approaches identified amino acid residues critical for coenzyme usage and enzyme activities

Morphological diversities and associated preference traits in Peanut (Arachis hypogaea L.) landraces from central and southern Benin

Peanut (Arachis hypogaea L.) production in Benin is limited by several biotic and abiotic stresses. The objectives of this study were to document varietal trait preferences and peanut genetic diversity for breeding programs. A survey in the South and Center of Benin and an agro-morphological characterization was carried out. Results showed that farmers used five criteria, namely yield (seeds and pods), size of seeds, number of seeds per pod, oil content, and quality of the paste for selecting a variety. The clustering based on ten qualitative traits showed a variability structure in three groups based on the leaflets shape, plant habit, and branching pattern. The principal component analysis carried out on the quantitative traits indicated six groups of accessions. The group 3 of the latest analysis is composed of Azii alorga and Kamalo with interesting characteristics and showing a good criteria as seeds size (SDL= 14.62 ± 0.48 mm), and pods size (average pod length and width respectively PoL = 33.70 ± 1.14 mm, Pow = 14.87 ± 0.29 mm). The results should be prioritized for breeding programs to improve the good criteria found in other peanut varieties. It will be helpful for farmers in selecting performant varieties