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Mol. Cells 2012; 33(1): 87-97

Published online November 29, 2011

https://doi.org/10.1007/s10059-012-2218-0

© The Korean Society for Molecular and Cellular Biology

Leaf Variegation in the Rice zebra2 Mutant Is Caused by Photoperiodic Accumulation of Tetra-Cis-Lycopene and Singlet Oxygen

Su-Hyun Han, Yasuhito Sakuraba, Hee-Jong Koh, and Nam-Chon Paek*

Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea

Correspondence to : *Correspondences: eycii@snu.ac.kr (EYC); hwyoun@snu.ac.kr (HY)

Received: October 18, 2011; Revised: November 10, 2011; Accepted: November 11, 2011

Abstract

In field conditions, the zebra2 (z2) mutant in rice (Oryza sativa) produces leaves with transverse pale-green/yellow stripes. It was recently reported that ZEBRA2 encodes carotenoid isomerase (CRTISO) and that low levels of lutein, an essential carotenoid for non-photochemical quen-ching, cause leaf variegation in z2 mutants. However, we found that the z2 mutant phenotype was completely suppressed by growth under continuous light (CL; permissive) conditions, with concentrations of chlorophyll, carotenoids and chloroplast proteins at normal levels in z2 mutants under CL. In addition, three types of reactive oxygen species (ROS; superoxide [O2-], hydrogen peroxide [H2O2], and singlet oxygen [1O2]) accumulated to high levels in z2 mutants grown under short-day conditions (SD; alternate 10-h light/14-h dark; restrictive), but do not ac-cumulate under CL conditions. However, the levels of lutein and zeaxanthin in z2 leaves were much lower than normal in both permissive CL and restrictive SD growth conditions, indicating that deficiency of these two carotenoids is not responsible for the leaf variegation phenotype. We found that the CRTISO substrate tetra-cis-lycopene accumulated during the dark periods under SD, but not under CL conditions. Its accumulation was also positively correlated with 1O2 levels generated during the light period, which consequently altered the expression of 1O2-res-ponsive and cell death-related genes in the variegated z2 leaves. Taking these results together, we propose that the z2 leaf variegation can be largely attributed to photoperiodic accumulation of tetra-cis-lycopene and generation of excessive 1O2 under natural day-night conditions.

Keywords carotenoid isomerase, rice, singlet oxygen, tetra-cis-lycopene, zebra2

Article

Research Article

Mol. Cells 2012; 33(1): 87-97

Published online January 31, 2012 https://doi.org/10.1007/s10059-012-2218-0

Copyright © The Korean Society for Molecular and Cellular Biology.

Leaf Variegation in the Rice zebra2 Mutant Is Caused by Photoperiodic Accumulation of Tetra-Cis-Lycopene and Singlet Oxygen

Su-Hyun Han, Yasuhito Sakuraba, Hee-Jong Koh, and Nam-Chon Paek*

Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea

Correspondence to:*Correspondences: eycii@snu.ac.kr (EYC); hwyoun@snu.ac.kr (HY)

Received: October 18, 2011; Revised: November 10, 2011; Accepted: November 11, 2011

Abstract

In field conditions, the zebra2 (z2) mutant in rice (Oryza sativa) produces leaves with transverse pale-green/yellow stripes. It was recently reported that ZEBRA2 encodes carotenoid isomerase (CRTISO) and that low levels of lutein, an essential carotenoid for non-photochemical quen-ching, cause leaf variegation in z2 mutants. However, we found that the z2 mutant phenotype was completely suppressed by growth under continuous light (CL; permissive) conditions, with concentrations of chlorophyll, carotenoids and chloroplast proteins at normal levels in z2 mutants under CL. In addition, three types of reactive oxygen species (ROS; superoxide [O2-], hydrogen peroxide [H2O2], and singlet oxygen [1O2]) accumulated to high levels in z2 mutants grown under short-day conditions (SD; alternate 10-h light/14-h dark; restrictive), but do not ac-cumulate under CL conditions. However, the levels of lutein and zeaxanthin in z2 leaves were much lower than normal in both permissive CL and restrictive SD growth conditions, indicating that deficiency of these two carotenoids is not responsible for the leaf variegation phenotype. We found that the CRTISO substrate tetra-cis-lycopene accumulated during the dark periods under SD, but not under CL conditions. Its accumulation was also positively correlated with 1O2 levels generated during the light period, which consequently altered the expression of 1O2-res-ponsive and cell death-related genes in the variegated z2 leaves. Taking these results together, we propose that the z2 leaf variegation can be largely attributed to photoperiodic accumulation of tetra-cis-lycopene and generation of excessive 1O2 under natural day-night conditions.

Keywords: carotenoid isomerase, rice, singlet oxygen, tetra-cis-lycopene, zebra2

Mol. Cells
Mar 31, 2023 Vol.46 No.3, pp. 131~189
COVER PICTURE
The physiologically important cytoprotective signaling in normal cells (background area in turquoise) mediated by NRF2 (blue chain) is often hijacked by cancer cells (red ball) in the tumor microenvironment (yellow area). However, the differential roles of NRF2 throughout the multistage carcinogenesis remains largely unresolved (white-colored overlapping misty areas).

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