Analyse fonctionnelle des enzymes de branchement de l'amidon de la feuille d'Arabidopsis thaliana

Trois gènes qui codent potentiellement des enzymes de branchement sont retrouvés dans le génome d'Arabidopsis thaliana: AtBE1, AtBE2 et AtBE3. Bien qu'aucun impact sur la structure de l'amidon ne fut observé dans les mutants Atbe1, des modifications sur la structure de l'amylopectine analogues à celles rencontrés chez d'autres mutants d'enzyme de branchement de type II furent détectées dans les mutants Atbe2 et Atbe3. Aucune modification du contenu en amidon ne fut repérée dans les lignées simple mutantes. Par ailleurs, nous avons produit les trois combinaisons de double mutant (Atbe1 /Atbe2, Atbe1/Atbe3, Atbe2/Atbe3) et avons analysé l'impact des mutations sur le contenu et la structure de l'amidon. Nos résultats montrent que AtBE1 ne possède apparemment aucune fonction dans la synthèse d'amidon dans les feuilles puisque les deux double mutants Atbe1/Atbe2 et Atbe1/Atbe3 affichent les mêmes phénotypes que les mutants Atbe2 et Atbe3. Toutefois, la synthèse d'amidon est supprimée dans le double mutant Atbe2/Atbe3 alors que de fortes quantités de a-maltose sont localisées dans le cytosol. Ce résultat indique que les fonctions des deux enzymes de branchement de type II AtBE2 et AtBE3 sont fortement redondantes chez Arabidopsis. De plus, nous avons démontré d'une part que l'accumulation de ce maltose dépend de la présence d'une forme active d'ADP-Glucose Pyrophosphorylase et d'autre part que la transglucosidase cytosolique (DPE2), impliquée dans la métabolisation du maltose, était spécifique du b-maltose.LILLE1-BU (590092102) / SudocSudocFranceF

Identification of suitable qPCR reference genes in leaves of Brassica oleracea under abiotic stresses

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Mutants of Arabidopsis Lacking Starch Branching Enzyme II Substitute Plastidial Starch Synthesis by Cytoplasmic Maltose Accumulation

Three genes, BE1, BE2, and BE3, which potentially encode isoforms of starch branching enzymes, have been found in the genome of Arabidopsis thaliana. Although no impact on starch structure was observed in null be1 mutants, modifications in amylopectin structure analogous to those of other branching enzyme II mutants were detected in be2 and be3. No impact on starch content was found in any of the single mutant lines. Moreover, three double mutant combinations were produced (be1 be2, be1 be3, and be2 be3), and the impact of the mutations on starch content and structure was analyzed. Our results suggest that BE1 has no apparent function for the synthesis of starch in the leaves, as both be1 be2 and be1 be3 double mutants display the same phenotype as be2 and be3 separately. However, starch synthesis was abolished in be2 be3, while high levels of α-maltose were assayed in the cytosol. This result indicates that the functions of both BE2 and BE3, which belong to class II starch branching enzymes, are largely redundant in Arabidopsis. Moreover, we demonstrate that maltose accumulation depends on the presence of an active ADP-glucose pyrophosphorylase and that the cytosolic transglucosidase DISPROPORTIONATING ENZYME2, required for maltose metabolization, is specific for β-maltose

The genus Resinicium in French Guiana and the West Indies: a morphological and molecular survey, revealing <em>Resinicium grandisporum sp nov.</em>

International audienceA revision of Resinicium collections (Basidiomycota, Hymenochaetales) from French Guiana and French West Indies is provided, and a new species, Resinicium grandisporum sp. nov., supported by morphological as well as phylogenetic analyses based on ITS rDNA sequences, is described and illustrated. An updated key of the genus Resinicium is also provided, which includes species previously described from outside of the studied area

Impact of cadmium on forage kale (Brassica oleracea var. viridis cv \textquotedblleftProver\textquotedblright) after 3-,10- and 56-day exposure to a Cd-spiked field soil

ACLCadmium (Cd) is a highly toxic element for living organisms and is widespread in metal-contaminated soils. As organisms which can grow up on these polluted areas, plants have some protection mechanisms against Cd issues. Among the plant kingdom, the Brassicaceae family includes species which are known to be able to tolerate and accumulate Cd in their tissues. In this study, Brassica oleracea var. viridis cv “Prover” was exposed to a range of artificially Cd-contaminated soils (from 2.5 up to 20 mg kg−1) during 3, 10, and 56 days and the effects on life traits, photosynthesis activity, antioxidant enzymatic activities were studied. Metal accumulation was quantified, as well as DNA damage, by means of the comet assay and immunodetection of 8-OHdG levels. Globally, B. oleracea was relatively tolerant to those Cd exposures. However, comet assay and detection of 8-OHdG revealed some DNA damage but which are not significant. According to metal accumulation analysis, B. oleracea var. viridis cv Prover could be a good candidate for alternative growing in contaminated areas

Antioxidant responses of Annelids, Brassicaceae and Fabaceae to pollutants: A review

International audienc

Cellulariella warnieri (Basidiomycota, Polyporales) and its doubles

International audienc

Antioxidant defense gene analysis in Brassica oleracea and Trifolium repens exposed to Cd and/or Pb

International audienc

Mutants of Arabidopsis Lacking a Chloroplastic Isoamylase Accumulate Phytoglycogen and an Abnormal Form of Amylopectin

Mutant lines defective for each of the four starch debranching enzyme (DBE) genes (AtISA1, AtISA2, AtISA3, and AtPU1) detected in the nuclear genome of Arabidopsis (Arabidopsis thaliana) were produced and analyzed. Our results indicate that both AtISA1 and AtISA2 are required for the production of a functional isoamylase-type of DBE named Iso1, the major isoamylase activity found in leaves. The absence of Iso1 leads to an 80% decrease in the starch content in both lines and to the accumulation of water-soluble polysaccharides whose structure is similar to glycogen. In addition, the residual amylopectin structure in the corresponding mutant lines displays a strong modification when compared to the wild type, suggesting a direct, rather than an indirect, function of Iso1 during the synthesis of amylopectin. Mutant lines carrying a defect in AtISA3 display a strong starch-excess phenotype at the end of both the light and the dark phases accompanied by a small modification of the amylopectin structure. This result suggests that this isoamylase-type of DBE plays a major role during starch mobilization. The analysis of the Atpu1 single-mutant lines did not lead to a distinctive phenotype. However, Atisa2/Atpu1 double-mutant lines display a 92% decrease in starch content. This suggests that the function of pullulanase partly overlaps that of Iso1, although its implication remains negligible when Iso1 is present within the cell