The new role of carbonic anhydrases and bicarbonate in acclimatization and hypoxia stress responses in Arabidopsis thaliana

Plant growth and stress responses largely depend on the chloroplast retrograde signaling. Stoichiometry of carbon dioxide assimilation and transpiration, efficiency of photosynthesis, and absorbed energy fate in photosystems between photochemistry, fluorescence and heat channels impact on the chloroplast retrograde signaling. Recent studies revealed that 22 kDa photosystem II protein (PsbS) and plant β carbonic anhydrases (βCAs), except their obvious functions, are also involved in regulation of plant stress responses. Obtained results suggest that simultaneous overexpression of βCA1 and/or βCA2 with PsbS genes leads to improved photoprotection, acclimation to variable light conditions, and water use efficiency. However, this was achieved on the costs of lower biomass gain in double and triple (oePsbSoeβCA1 and oePsbSoeβCA1βCA2, respectively) transgenic lines in comparison to Col-0, and npq4-1 mutant. After bicarbonate fertilization we observed significant increase in biomass production in triple transgenic lines compared to oePsbS and npq4-1 plants, but not to Col-0. Transcriptomic analysis revealed that bicarbonate treatment of double and triple transgenic lines specifically induced expression of genes and transcription factors related to hypoxia, freezing, drought, high light, and pathogen attack stress responses, contrary to other genotypes. Interestingly, expression of two of these transcription factors, DREB - CBF2 subfamily (A-1 of ERF/AP2), and BT2 were reduced in oe PsbS transgenic line. Our results suggest a novel regulatory role of βCAs and bicarbonate in the regulation of stress responses and plant productivity.