Effect of CAX1a TILLING mutations on photosynthesis performance in salt-stressed Brassica rapa plants

Abstract

Salinity is an important environmental factor that reduces plant productivity in many world regions. It affects negatively photosynthesis causing a growth reduction. Likewise, calcium (Ca2+) is crucial in plant stress response. Therefore, the modification of Ca2+ cation exchangers (CAX) transporters could be a potential strategy to increase plant tolerance to salinity. Using Targeting Induced Local Lesions in Genomes (TILLING), researchers generated three mutants of Brassica rapa CAX1a transporter. The aim of this study was to test the effect of those mutations on salt tolerance focusing on the response to the photosynthesis process. Thus, BraA.cax1a and R-o-18 plants were grown under salinity conditions, and parameters related to biomass, photosynthesis performance, glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49), and soluble carbohydrates were measured. The results showed that BraA.cax1a-4 mutation provided higher biomass and a better photosynthetic performance manifested by a higher water use efficiency (WUE), higher Fv/Fm, electron fluxes, and a higher Rubisco (EC 4.1.1.39) accumulation. In addition, BraA.cax1a-4 presented increased osmotic protection through myo-inositol accumulation. On the other hand, BraA.cax1a-7 produced some negative effects on photosynthesis performance and lower G6PDH and Rubisco accumulations. Therefore, this study points out BraA.cax1a-4 as a useful mutation to improve photosynthetic performance in plants grown under saline conditions.