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

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 quenching, 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. ]) accumulated to high levels in z2 mutants grown under short-day conditions (SD; alternate 10-h light/14-h dark; restrictive), but do not accumulate 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 1 O 2 levels generated during the light period, which consequently altered the expression of 1 O 2 -responsive 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 1 O 2 under natural day-night conditions.

The Exogenous Application of Abscisic Acid Induce Accumulation of Anthocyanins and Phenolic Compounds of the ‘Rubi’ Grape

“…According to Han et al [34], the carotenoids have been described for maintaining the cell wall integrity and the efficiency of this pigment as an antioxidant against injuries promoted by ROS depends on the synergistic interaction with flavonoids and with other carotenoids. In this way, the positive correlation found between carotenoids and flavonoids can be attributes to the synergic action and antioxidant of both phytochemicals.…”

Two NADPH: Protochlorophyllide Oxidoreductase (POR) Isoforms Play Distinct Roles in Environmental Adaptation in Rice

“…The excitation and emission wavelengths were 480 nm and 520 nm, respectively. Detection of hydrogen peroxide and superoxide by 3,3-diaminobendizine (DAB) and nitroblue tetrazolium chloride (NBT) staining, respectively, was performed as previously described (Han et al 2012). …”

“…Photosynthesis-related and OsPOR proteins were detected as previously described, with some modifications (Han et al 2012; Kwon et al 2015a). Leaf tissue (10 mg) was homogenized in 100 μl of SDS sample buffer (50 mM Tris, pH 6.8, 2 mM EDTA, 10% w/v glycerol, 2% SDS, and 6% β-mercaptoethanol), and the extracted proteins were denatured at 100 °C for 3 min, resolved by SDS-PAGE, and immunoblotted.…”

Cloning and functional analysis of pale-green leaf (PGL10) in rice (Oryza sativa L.)

“…abnormal phenotypes (e.g., yellow, pale green, spots, stripes, pale yellow, and albino; Gustafsson 1940). The resulting mutant genes often directly or indirectly influence chlorophyll synthesis and degradation in leaves (Han et al 2012), which negatively affect plant photosynthesis, leading to yield loss and even rice plant death (He et al 2006;Zhang et al 2010).…”