Chlorophyllide-a Oxygenase 1 (OsCAO1) Over-Expression Affects Rice Photosynthetic Rate and Grain Yield

doi:10.1016/j.rsci.2022.05.006

Abstract

Abstract: Leaf color and photosynthesis are important factors for rice growth and development. Hence, improving the photosynthetic rate is an effective approach for increasing rice yield. We isolated a gene, chlorophyllide-a oxygenase 1 (OsCAO1), which characterized a rice near-isogenic line named fgl (faded green leaf). Compared with its recurrent parent, Zhefu 802 (ZF802, an early-season indica rice variety), fgl had a faded green leaf color and lower chlorophyll (Chl) content, especially Chl b content. Furthermore, genetic and physiological analysis confirmed that leaf color was affected by the novel allele OsCAO1, which had a two-base pair deletion in the ninth exon. Subsequently, we over-expressed the OsCAO1 gene in ZF802. Interestingly, while OsCAO1 over-expression (OX) increased Chl b synthesis, the OX plants had a higher photosynthetic rate and heavier 1000-grain weight than ZF802. In conclusion, the novel allele OsCAO1 was involved in the positive regulation of leaf color, photosynthetic rate and rice yield.

Hu Ping, Ma Jie, Kang Shujing, Li Sanfeng, Wu Xianmei, Zeng Longjun, Lu Caolin, He Rui, He Huiying, Shang Lianguang, Rao Yuchun, Zhu Xudong, Xiong Guosheng, Qian Qian, Guo Longbiao, Wang Yuexing. Chlorophyllide-a Oxygenase 1 (OsCAO1) Over-Expression Affects Rice Photosynthetic Rate and Grain Yield[J]. Rice Science, 2023, 30(2): 87-91.

Figures/Tables 1

Fig. 1. Characterizations of the recurrent parent Zhefu 802 (ZF802), near-isogenic line fgl and over-expression (OX) plants, and map-based cloning, identification and confirmation of the OsCAO1 gene in rice. A, Phenotypes of ZF802 and fgl at the seedling stage. Bars, 5 cm. B-H, Chlorophyll (Chl) content, including Chl a content (B1), Chl b content (B2), total Chl content (B3) and ratio of Chl a to Chl b (B4), plant height (C), tiller number (D), No. of grains per panicle (E), 1000-grain weight (F), grain weight per plant (G), and seed-setting rate (H) of ZF802 and fgl. I, Fine mapping of OsCAO1 locus. ORF, Open reading frame. J, Exon/intron structure and the mutation site of OsCAO1. Closed boxes indicate exons, and the lines between the exons indicate introns in OsCAO1. A red triangle indicates the mutation point. K, Phenotypes of ZF802 and OXs (OX-1 and OX-2) at the heading stage. Bar, 20 cm. L, OsCAO1 expression levels as detected by qRT-PCR (n = 4). M-Z, Total Chl content (M1), Chl b content (M2), ratio of Chl a to Chl b (M3), net photosynthetic rate (Pn) (N), stomatal conductance (Cond) (n = 3) (O), abscisic acid (ABA) content (P), H2O2 content (Q), catalase (CAT) activity (R), peroxidase (POD) activity (n = 3) (S), plant height (T), tiller number (U), panicle length (V), No. of grains per panicle (W), 1000-grain weight (X), grain weight per plant (Y), seed-setting rate (n = 8) (Z) of ZF802 and OX (OX-1 and OX-2) plants. Values in B-H and L-Z are Mean ± SD. * and ** indicate the significant differences at the 0.05 and 0.01 levels, respectively, by the Student’s t-test, while ns indicates no significance.

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