Journal
PLANTA
Volume 236, Issue 5, Pages 1639-1652Publisher
SPRINGER
DOI: 10.1007/s00425-012-1710-2
Keywords
BnCBF17-over-expression; Brassica; Cold acclimation; Energy conversion efficiency; Long-term elevated CO2; Photosynthesis
Categories
Funding
- Natural Sciences and Engineering Research Council (NSERC)
- Green Crop Research Network (GCN)
- NSERC Discovery Grant
- Canada Research Chair program
- Canada Foundation for Innovation
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The effects of cold acclimation and long-term elevated CO2 on photosynthetic performance of wild-type (WT) and BnCBF17-over-expressing line of Brassica napus cv. Westar (BnCBF17-OE) grown at either 20/16 A degrees C (non-acclimated) or 5/5 A degrees C (cold acclimated) and at either ambient (380 mu mol C mol(-1)) or elevated (700 mu mol C mol(-1)) CO2 were studied. Compared with non-acclimated WT, the BnCBF17-OE grown at 20 A degrees C mimicked the effects of cold acclimation on WT B. napus with respect to compact dwarf phenotype and increased rates of light-saturated CO2 assimilation and photosynthetic electron transport. This was associated with enhanced energy conversion efficiency into biomass as assessed by decreased excitation pressure coupled to decreased dependence on non-photochemical energy dissipation for a given irradiance. Growth at elevated CO2 decreased the light and CO2-saturated rates of photosynthesis by 30 % for non-acclimated WT relative to growth at ambient CO2. This was associated with inhibition in electron transport rates (20 %), decrease in amount of rbcL (35 %) and cytosolic FBPase (70 %) and increased excitation pressure and non-photochemical quenching in elevated versus ambient CO2-grown non-acclimated WT. In contrast, light and CO2-saturated rates of photosynthesis, electron transport, excitation pressure, non-photochemical quenching and levels of rbcL, cytosolic FBPase and Lhcb1 were insensitive to growth under elevated CO2 in BnCBF17-OE and cold-acclimated WT. Thus, BnCBF17-over-expression and cold acclimation maintain enhanced energy conversion efficiency and reduced sensitivity to feedback-limited photosynthesis during long-term growth of B. napus under elevated CO2. Our results indicated that CBFs transcription factors regulate not only freezing tolerance but also has major whole plant effects.
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