Sixteen cytosolic glutamine synthetasegenesidentified in theBrassica napusL. genome are differentially regulated depending on nitrogen regimes and leaf senescence

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A total of 16BnaGLN1genes coding for cytosolic glutamine synthetase isoforms (EC were found in theBrassica napusgenome. The total number ofBnaGLN1genes, their phylogenetic relationships, and genetic locations are in agreement with the evolutionary history ofBrassicaspecies. TwoBnaGLN1.1, twoBnaGLN1.2, sixBnaGLN1.3, fourBnaGLN1.4, and twoBnaGLN1.5 genes were found and named according to the standardized nomenclature for theBrassicagenus. Gene expression showed conserved responses to nitrogen availability and leaf senescence among the Brassiceae tribe. TheBnaGLN1.1andBnaGLN1.4families are overexpressed during leaf senescence and in response to nitrogen limitation. TheBnaGLN1.2family is up-regulated under high nitrogen regimes. The members of theBnaGLN1.3family are not affected by nitrogen availability and are more expressed in stems than in leaves. Expression of the twoBnaGLN1.5genes is almost undetectable in vegetative tissues. Regulations arising from plant interactions with their environment (such as nitrogen resources), final architecture, and therefore sink-source relationsin planta, seem to be globally conserved betweenArabidopsisandB. napus. Similarities of the coding sequence (CDS) and protein sequences, expression profiles, response to nitrogen availability, and ageing suggest that the roles of the differentGLN1families have been conserved among the Brassiceae tribe. These findings are encouraging the transfer of knowledge from theArabidopsismodel plant to theB. napuscrop plant. They are of special interest when considering the role of glutamine synthetase in crop yield and grain quality in maize and wheat.

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