Functional redundancy and divergence of ß-carbonic anhydrases in Physcomitrella patens.

ABSTRACT

MAIN CONCLUSION: ß-carbonic anhydrases, which function in regulating plant growth, C/N status, and stomata number, showed functional redundancy and divergence in Physcomitrella patens. Carbonic anhydrases (CAs) catalyze the interconversion of CO2 and HCO3-. Plants have three evolutionarily unrelated CA families α-, ß-, and γ-CAs. ßCAs are abundant in plants and are involved in CO2 assimilation, stress responses, and stomata formation. Recent studies of ßCAs have mainly examined C3 or C4 plants, whereas their functions in non-vascular plants are mostly unknown. In this study, phylogenetic analysis revealed that the evolution of ßCAs were conserved between subaerial green algae and bryophytes after terrestrialization event, and ßCAs from some cyanobacteria might begin evolving for the adaptation of terrestrial environment/habitat. In addition, we investigated the physiological roles of ßCAs in the basal land plant Physcomitrella patens. High PpßCA expression levels in different tissues suggest that PpßCAs play important roles in development in P. patens. Plants treated with 1-10 mM NaHCO3 had higher fresh and dry weight, PpßCA expression, total CA activity, and photosynthetic yield (Fv/Fm) compared with water-treated plants. However, treatment with 10 mM NaHCO3 influenced the C/N status. Further study of six Ppßca single-gene mutants revealed that PpßCAs have functional redundancy and divergence in regulating the C/N ratio of plants and stomatal formation. This study provides new insight into the physiological roles of ßCAs in basal land plants.