Key message

The altered rice leaf color based on the knockout of CAO1 gene generated using CRISPR/Cas9 technology plays important roles in chlorophyll degradation and ROS scavenging to regulate both natural and induced senescence in rice.

Abstract

Rice chlorophyllide a oxygenase (OsCAO1), identified 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 flag 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 identified 580 up-regulated and 206 downregulated genes in the edited lines. The differentially expressed genes (DEGs) involved in chlorophyll biosynthesis, magnesium chelatase subunit (CHLH), and glutamate-1-semialdehyde2, 1-aminomutase (GSA) metabolism decreased significantly. Meanwhile, the gel consistency (GC) levels of rice grains, chalkiness ratios and chalkiness degrees (CD) decreased in the edited lines. Thus, knockout of OsCAO1 influenced 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.

中文翻译：

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使用 CRISPR/Cas9 系统对水稻 OsCAO1 敲除系进行转录组学和生理学分析

关键信息

基于使用 CRISPR/Cas9 技术产生的 CAO1 基因敲除而改变的水稻叶色在叶绿素降解和 ROS 清除中发挥重要作用，从而调节水稻的自然衰老和诱导衰老。

抽象的

水稻叶绿素a加氧酶（OsCAO1）被鉴定为光照条件下的叶绿素b合成酶，在调控水稻植物光合作用中起关键作用。在这项研究中，报告了通过敲除OsCAO1基因（称为叶绿素合成过程）开发具有淡绿色叶子的编辑品系。_{181 T 0}中的 81 个基因编辑品系植物是通过 CRISPR/Cas9 系统生成的。与野生型'东津'植物（WT）相比，编辑的线条具有短而窄的旗叶和淡绿色的叶子。此外，经过编辑的品系在幼苗期和成熟期都具有较低的叶绿素 b 和类胡萝卜素含量。转录组分析确定了编辑品系中的 580 个上调基因和 206 个下调基因。参与叶绿素生物合成、镁螯合酶亚基 (CHLH) 和谷氨酸-1-半醛 2、1-氨基变位酶 (GSA) 代谢的差异表达基因 (DEG) 显着下降。同时，编辑品系中米粒的凝胶稠度（GC）水平、垩白比和垩白度（CD）降低。因此，敲除OsCAO1影响水稻生育期、叶片发育和籽粒品质性状。总体而言，结果表明OsCAO1在叶绿素降解和 ROS 清除中也发挥重要作用，从而调节水稻的自然衰老和诱导衰老。