Verdun 1916 : mythes et réalités

Activités « Hors les murs

Sortie d’automne dans la Meuse: de Metz à Hattonchâtel par la Voie sacrée et la Route Ligier Richier

Activités « Hors les murs

Efecto del envejecimiento acelerado sobre la composición lipídica de semillas de dos variedades de trigo blando de Marruecos

The lipid composition of the seeds from two soft wheat varieties (Triticum aestivum, cv. Marchouche and Mahdia) were analyzed before and after accelerated aging. Eight days of accelerated aging resulted in a total inhibition of seed germinability as well as a decrease in their total and especially unsaturated fatty acid contents. Oleic and linoleic acid contents decreased particularly in the phosphatidylcholine of the seeds from both varieties. The proportion of polar lipids also decreased after aging as compared to neutral lipids: a 5.8% and 7.2% decrease in polar lipids was e observed in Mahdia and Marchouche cultivars, respectively. In the neutral lipids of the seeds from the Marchouche variety, the percentage of free fatty acids increased whereas the triacylglycerols decreased. After aging, the fatty acid compositions of all lipid classes were modified in the same manner as total fatty acid compositions. Among polar lipids, phospholipid proportions were particularly small, especially the phosphatidylcholine percentages with an 18.1% and 19.1% decrease in Mahdia and Marchouche varieties, respectively. In contrast, MGDG percentages increased, especially in the seeds from the Marchouche variety. A 15.5% increase was noticed when compared with seeds which were not aged. At the same time, the DGDG percentage showed a 16.6% decrease after accelerated aging of the seeds from the Marchouche variety. From these results we concluded that the lipid content decrease observed in seeds after accelerated aging could be linked to a loss in the germination and vigor of wheat seeds.La composición lipídica de semillas de dos variedades de trigo blando (Triticum aestivum, cv. Marchouche and Mahdia) fueron analizadas antes y después del envejecimiento acelerado. Ocho días de envejecimiento acelerado provoco una inhibición total de la geminabilidad, así como un descenso en el contenido total de ácidos grasos, en especial de los ácidos grasos insaturados. Los contenidos del ácido oleico y linoleico disminuyeron particularmente, en la fosfatidilcolina de las semillas de ambas variedades. La proporción de lípidos polares también decreció después del envejecimiento en comparación con los lípidos neutros: un descenso del 5.8% y 7.2% de los lípidos polares fueron observados en los cultivos de Mahdia y Marchouche, respectivamente. En los lípidos de las semillas de la variedad Marchouche, el porcentaje de ácidos grasos libres aumento, mientras que los triglicéridos decrecieron. Después del envejecimiento, la composición de los ácidos grasos de todas las clases de lípidos fue modificada de la misma manera que la composición de los ácidos grasos totales. Entre los lípidos polares, la proporción de fosfolípidos fue la que disminuyo principalmente, en especial el porcentaje de fosfatidilcolina: un 18.1% y 19.1% para las variedades Mahdia y Marchouche, respectivamente. Por otra parte, los porcentajes de MGDG aumentaron, en especial en las semillas de la variedad Marchouche: un 15.5% en comparación con las semillas no envejecidas. Al mismo tiempo, los porcentajes de DGDG mostraron un descenso del 16.6% después del envejecimiento acelerado de semillas de la variedad Marchouche. De todos estos resultados, se concluye que el descenso del contenido lipídico observado en semillas después del envejecimiento acelerado podría estar relacionado con una pérdida de germinación y de vigor de semillas de trigo

Phytosphingosine-phosphate is a signal for AtMPK6 activation and Arabidopsis response to chilling

Long-chain bases (LCBs) are pleiotropic sphingolipidic signals in eukaryotes. We investigated the source and function of phytosphingosine-1-phosphate (PHS-P), a phospho-LCB rapidly and transiently formed in Arabidopsis thaliana on chilling.PHS-P was analysed by thin-layer chromatography following in vivo metabolic radiolabelling. Pharmacological and genetic approaches were used to identify the sphingosine kinase isoforms involved in cold-responsive PHS-P synthesis. Gene expression, mitogen-activated protein kinase activation and growth phenotypes of three LCB kinase mutants (lcbk1, sphk1 and lcbk2) were studied following cold exposure. Chilling provoked the rapid and transient formation of PHS-P in Arabidopsis cultured cells and plantlets. Cold-evoked PHS-P synthesis was reduced by LCB kinase inhibitors and abolished in the LCB kinase lcbk2 mutant, but not in lcbk1 and sphk1 mutants. lcbk2 presented a constitutive AtMPK6 activation at 22°C. AtMPK6 activation was also triggered by PHS-P treatment independently of PHS/PHS-P balance. lcbk2 mutants grew comparably with wild-type plants at 22 and 4°C, but exhibited a higher root growth at 12°C, correlated with an altered expression of the cold-responsive DELLA gene RGL3. Together, our data indicate a function for LCBK2 in planta. Furthermore, they connect PHS-P formation with plant response to cold, expanding the field of LCB signalling in plants