Transcriptomic and physiological analysis of OsCAO1 knockout lines using the CRISPR/Cas9 system in rice

Abstract

Rice chlorophyllide a oxygenase (OsCAO1), identifed as the chlorophyll b synthesis under light condition, plays a critical role in regulating rice plant photosynthesis. In this study, the development of edited lines with pale green leaves by knockout of OsCAO1 gene known as a chlorophyll synthesis process is reported. Eighty-one genetically edited lines out of 181 T0 plants were generated through CRISPR/Cas9 system. The edited lines have short narrow fag leaves and pale green leaves compared with wild-type ‘Dongjin’ plants (WT). Additionally, edited lines have lower chlorophyll b and carotenoid contents both at seedling and mature stages. A transcriptome analysis identifed 580 up-regulated and 206 downregulated genes in the edited lines. The diferentially expressed genes (DEGs) involved in chlorophyll biosynthesis, magnesium chelatase subunit (CHLH), and glutamate-1-semialdehyde2, 1-aminomutase (GSA) metabolism decreased signifcantly. Meanwhile, the gel consistency (GC) levels of rice grains, chalkiness ratios and chalkiness degrees (CD) decreased in the edited lines. Thus, knockout of OsCAO1 infuenced growth period, leaf development and grain quality characters of rice. Overall, the result suggests that OsCAO1 also plays important roles in chlorophyll degradation and ROS scavenging to regulate both natural and induced rice senescence.