科研之友
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摘要
Thioredoxins f (Trxf) are chloroplastic proteins that have been shown to be essential for the redox-based regulation of several steps of carbon assimilation, such as the Calvin-Benson-Bassham cycle. However, the effective impact of Trx f activity on photosynthetic performance and carbon primary metabolism, including under varying CO2 mole fraction, is not well documented. In this study, we provide a physiological and metabolomic characterization of leaves in transplastomic Trxf over-expressing tobacco (Nicotiana tabacum L., cv. Petit Havana SRI) grown under either ambient or elevated CO2 (400 or 800 mu mol mol(-1)). Trx f overexpression strongly increased starch synthesis under both ambient and elevated CO2 but was not accompanied by a stimulation of net photosynthetic CO2 fixation. Rather, Trx f-overexpressing plants had a lower photorespiration rate due to an increase in internal (mesophyll) conductance for CO2 (with the consequent increase in CO2 mole fraction at the carboxylation site, cc), and a higher decrease (compared with the wild-type) in total photosynthetic electron flux upon acclimation to elevated CO2. There were also changes in a number of metabolites, such as enrichment in sugar phosphates and free phosphate, and depletion in alanine, threonine and free sugars. Our results suggest that over-expressing Trx f has an influence on chloroplastic metabolism by simultaneously stimulating the carboxylation-to-oxygenation ratio and starch synthesis, with side effects on amino acid metabolism. The potential mechanisms involved are discussed.
- 出版日期2015-10
