Overexpression of thioredoxin m in chloroplasts alters carbon and nitrogen partitioning in tobacco

• Published in: Journal of experimental botany Vol. 72; no. 13; pp. 4949 - 4964
• Main Authors: Ancín, María, Larraya, Luis, Florez-Sarasa, Igor, Bénard, Camille, Fernández-San Millán, Alicia, Veramendi, Jon, Gibon, Yves, Fernie, Alisdair R, Aranjuelo, Iker, Farran, Inmaculada
• Format: Journal Article
• Language: English
• Published: UK Oxford University Press 22.06.2021
• Subjects: Carbon - metabolism; Chloroplast Thioredoxins - metabolism; Chloroplasts - metabolism; Gene Expression Regulation, Plant; Nicotiana - genetics; Nicotiana - metabolism; Nitrogen - metabolism; Plants, Genetically Modified - genetics; Plants, Genetically Modified - metabolism; Research Papers; photorespiration; chloroplast; glutamine synthetase; GS-GOGAT pathway; thioredoxin; nitrogen metabolism; Carbon metabolism
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jxb/erab193

Abstract In 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. Thioredoxin m overexpression modulates carbon and nitrogen partitioning in plants by regulating the photorespiratory nitrogen cycle, where an increase of activity and stability of glutamine synthetase was shown.