Ancín Rípodas, MaríaLarraya Reta, Luis MaríaFlorez-Sarasa, IgorBénard, CamilleFernández San Millán, AliciaVeramendi Charola, JonGibon, YvesFernie, Alisdair R.Aranjuelo Michelena, IkerFarrán Blanch, Inmaculada2021-12-302021-12-3020210022-095710.1093/jxb/erab193https://academica-e.unavarra.es/handle/2454/41656In plants, there is a complex interaction between carbon (C) and nitrogen (N) metabolism, and its coordination is fundamental for plant growth and development. Here, we studied the influence of thioredoxin (Trx) m on C and N partitioning using tobacco plants overexpressing Trx m from the chloroplast genome. The transgenic plants showed altered metabolism of C (lower leaf starch and soluble sugar accumulation) and N (with higher amounts of amino acids and soluble protein), which pointed to an activation of N metabolism at the expense of carbohydrates. To further delineate the effect of Trx m overexpression, metabolomic and enzymatic analyses were performed on these plants. These results showed an up-regulation of the glutamine synthetase-glutamate synthase pathway; specifically tobacco plants overexpressing Trx m displayed increased activity and stability of glutamine synthetase. Moreover, higher photorespiration and nitrate accumulation were observed in these plants relative to untransformed control plants, indicating that overexpression of Trx m favors the photorespiratory N cycle rather than primary nitrate assimilation. Taken together, our results reveal the importance of Trx m as a molecular mediator of N metabolism in plant chloroplasts.16 p.application/pdfeng© The Author(s) 2021. Creative Commons Attribution 4.0 InternationalCarbon metabolismChloroplastGlutamine synthetaseGS-GOGAT pathwayNitrogen metabolismPhotorespirationThioredoxininfo:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccess