Britta Förster et. al, Full list of authors in summary

LCIA (low CO₂-inducible protein A) is a chloroplast envelope protein associated with the CO₂-concentrating mechanism of the green alga Chlamydomonas reinhardtii. LCIA is postulated to be a HCO₃^– channel, but previous studies were unable to show that LCIA was actively transporting bicarbonate in planta. Therefore, LCIA activity was investigated more directly in two heterologous systems: an Escherichia coli mutant (DCAKO) lacking both native carbonic anhydrases and an Arabidopsis mutant (βca5) missing the plastid carbonic anhydrase βCA5. Neither DCAKO nor βca5 can grow in ambient CO₂ conditions, as they lack carbonic anhydrase-catalyzed production of the necessary HCO₃^– concentration for lipid and nucleic acid biosynthesis. Expression of LCIA restored growth in both systems in ambient CO₂ conditions, which strongly suggests that LCIA is facilitating HCO₃^– uptake in each system. To our knowledge, this is the first direct evidence that LCIA moves HCO₃^– across membranes in bacteria and plants. Furthermore, the βca5 plant bioassay used in this study is the first system for testing HCO₃^– transport activity in planta, an experimental breakthrough that will be valuable for future studies aimed at improving the photosynthetic efficiency of crop plants using components from algal CO₂-concentrating mechanisms.

 

Authors: Britta Förster, Loraine M Rourke, Hiruni N Weerasooriya, Isaiah C M Pabuayon, Vivien Rolland, Eng Kee Au, Soumi Bala, Joanna Bajsa-Hirschel, Sarah Kaines, Remmy W Kasili, Lillian M LaPlace, Marylou C Machingura, Baxter Massey, Viviana C Rosati, Hilary Stuart-Williams, Murray R Badger, G Dean Price, James V Moroney