Photosynthetic characterization of Rubisco transplantomic lines reveals alterations on photochemistry and mesophyll conductance
2013
Galmés, Jeroni | Perdomo, Juan Alejandro | Flexas, Jaume | Whitney, Spencer M.
Improving Rubisco catalysis is considered a promising way to enhance C₃-photosynthesis and photosynthetic water use efficiency (WUE) provided the introduced changes have little or no impact on other processes affecting photosynthesis such as leaf photochemistry or leaf CO₂ diffusion conductances. However, the extent to which the factors affecting photosynthetic capacity are co-regulated is unclear. The aim of the present study was to characterize the photochemistry and CO₂ transport processes in the leaves of three transplantomic tobacco genotypes expressing hybrid Rubisco isoforms comprising different Flaveria L-subunits that show variations in catalysis and differing trade-offs between the amount of Rubisco and its activation state. Stomatal conductance (g ₛ) in each transplantomic tobacco line matched wild-type, while their photochemistry showed co-regulation with the variations in Rubisco catalysis. A tight co-regulation was observed between Rubisco activity and mesophyll conductance (g ₘ) that was independent of g ₛ thus producing plants with varying g ₘ/g ₛ ratios. Since the g ₘ/g ₛ ratio has been shown to positively correlate with intrinsic WUE, the present results suggest that altering photosynthesis by modifying Rubisco catalysis may also be useful for targeting WUE.
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