第1247回生物科学セミナー
The role of cytosolic carbonic anhydrase activity for C3 photosynthesis
Dr. Bernard Genty（Commissariat à l'Energie Atomique et aux Energies Alternatives, Cadarache, France）
2018年11月01日(木) 16:50-18:00 理学部2号館 講堂
C3 mesophyll cells have a relatively high abundance of carbonic anhydrase
(CA) in the cytosol. The role of this cytosolic CA is puzzling considering that C3
plants in contrast to C4 plants do not sustain high phosphoenolpyruvate
carboxylase activity in the mesophyll. By using combined genetic and
functional approaches complemented with modelling, we addressed the
quantitative role of cytosolic CA activity for C3 photosynthesis. Using
18O-labelled CO2 and mass spectrometry for monitoring the rate of oxygen
atoms exchange between CO2 and mesophyll water, the kinetic properties of
CO2 diffusion and hydration into the leaf in vivo were investigated. Using
various CA knock-out mutants, we estimated CA activity in folio, particularly, in
the cytosol compartment, as well as the CO2 transfer conductance between the
atmosphere and the location of the different CA isoforms in the leaf. The
comparison between this CA-based assay and a classic assay of mesophyll
conductance (Rubisco-based) allowed us to describe the components of CO2
transfer in the liquid phase. Analysing the relationships between growth,
assimilation, mesophyll and stomatal conductances and their CO2 responses in
the light of the cellular localisation and activities of CAs, we evaluated the role
of cytosolic CAs in CO2 transport and in optimising efficiency of photosynthetic
carbon gain.
