Regulatory preconditioning for the evolution of C4photosynthesis revealed by low CO2treatment of Arabidopsis thaliana

Abstract

AbstractLow CO2condition was considered a preconditioning or selection pressure for C4evolution. However, it remains elucidated how low CO2condition contribute to the evolutionary assembly of the C4pathway. We conducted a systematic transcriptomics and metabolomics analysis under short-term low CO2condition and found thatArabidopsisgrown under this condition showed increased expression of most genes encoding C4- related enzymes and transporters. Low CO2condition increased NH4+content in leaves; as expected, photorespiratory and ammonia refixing pathways were enhanced. Furthermore, we found that compared to low CO2condition, in vitro treatment with NH4+induced a similar pattern of changes in C4related genes and genes involved in ammonia refixation. This supports that increased expression of C4genes induced by low CO2condition can supply carbon skeleton for ammonia recycling. This study provides new insight into the regulatory preconditioning which may have facilitated the evolution of C4photosynthesis under low atmospheric CO2environments.