OsαCA1 Affects Photosynthesis, Yield Potential, and Water Use Efficiency in Rice

Plant growth and crop yield are essentially determined by photosynthesis when considering carbon dioxide (CO2) availability. CO2 diffusion inside a leaf is one of the factors that dictate the CO2 concentrations in chloroplasts. Carbonic anhydrases (CAs) are zinc-containing enzymes that interconvert CO2 and bicarbonate ions (HCO3-), which, consequently, affect CO2 diffusion and thus play a fundamental role in all photosynthetic organisms. Recently, the great progress in the research in this field has immensely contributed to our understanding of the function of the beta-type CAs; however, the analysis of alpha-type CAs in plants is still in its infancy. In this study, we identified and characterized the Os alpha CA1 gene in rice via the analysis of Os alpha CAs expression in flag leaves and the subcellular localization of its encoding protein. Os alpha CA1 encodes an alpha-type CA, whose protein is located in chloroplasts with a high abundance in photosynthetic tissues, including flag leaves, mature leaves, and panicles. Os alpha CA1 deficiency caused a significant reduction in assimilation rate, biomass accumulation, and grain yield. The growth and photosynthetic defects of the Os alpha CA1 mutant were attributable to the restricted CO2 supply at the chloroplast carboxylation sites, which could be partially rescued by the application of an elevated concentration of CO2 but not that of HCO3-. Furthermore, we have provided evidence that Os alpha CA1 positively regulates water use efficiency (WUE) in rice. In summary, our results reveal that the function of Os alpha CA1 is integral to rice photosynthesis and yield potential, underscoring the importance of alpha-type CAs in determining plant physiology and crop yield and providing genetic resources and new ideas for breeding high-yielding rice varieties.

Automated summary

This study reveals the integral role of Os alpha CA1 in photosynthesis and yield potential in rice, highlighting the importance of alpha-type CAs in plant physiology and crop yield. It also provides genetic resources and new ideas for breeding high-yielding rice varieties.