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Mutations of genes in synthesis of the carotenoid precursors of ABA lead to pre-harvest sprouting and photo-oxidation in rice.

Fang J, Chai C, Qian Q, Li C, Tang J, Sun L, Huang Z, Guo X, Sun C, Liu M, Zhang Y, Lu Q, Wang Y, Lu C, Han B, Chen F, Cheng Z, Chu C - Plant J. (2008)

Bottom Line: Pre-harvest sprouting (PHS) or vivipary in cereals is an important agronomic trait that results in significant economic loss.As expected, the amount of ABA was reduced in all four phs mutants compared with that in the wild type.These results suggest that the impairment of carotenoid biosynthesis causes photo-oxidation and ABA-deficiency phenotypes, of which the latter is a major factor controlling the PHS trait in rice.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research, Beijing 100101, China.

ABSTRACT
Pre-harvest sprouting (PHS) or vivipary in cereals is an important agronomic trait that results in significant economic loss. A considerable number of mutations that cause PHS have been identified in several species. However, relatively few viviparous mutants in rice (Oryza sativa L.) have been reported. To explore the mechanism of PHS in rice, we carried out an extensive genetic screening and identified 12 PHS mutants (phs). Based on their phenotypes, these phs mutants were classified into three groups. Here we characterize in detail one of these groups, which contains mutations in genes encoding major enzymes of the carotenoid biosynthesis pathway, including phytoene desaturase (OsPDS), zeta-carotene desaturase (OsZDS), carotenoid isomerase (OsCRTISO) and lycopene beta-cyclase (beta-OsLCY), which are essential for the biosynthesis of carotenoid precursors of ABA. As expected, the amount of ABA was reduced in all four phs mutants compared with that in the wild type. Chlorophyll fluorescence analysis revealed the occurrence of photoinhibition in the photosystem and decreased capacity for eliminating excess energy by thermal dissipation. The greatly increased activities of reactive oxygen species (ROS) scavenging enzymes, and reduced photosystem (PS) II core proteins CP43, CP47 and D1 in leaves of the Oscrtiso/phs3-1mutant and OsLCY RNAi transgenic rice indicated that photo-oxidative damage occurred in PS II, consistent with the accumulation of ROS in these plants. These results suggest that the impairment of carotenoid biosynthesis causes photo-oxidation and ABA-deficiency phenotypes, of which the latter is a major factor controlling the PHS trait in rice.

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Photobleaching phenotype (a, b) and the detection of ROS (c, d) of Oscrtiso and β-LCY-RNAi plants and the corresponding wild types.
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fig06: Photobleaching phenotype (a, b) and the detection of ROS (c, d) of Oscrtiso and β-LCY-RNAi plants and the corresponding wild types.

Mentions: Due to the photoprotective function of carotenoids, plants deprived of these pigments suffered from photobleaching damage, especially under high light conditions (Niyogi, 1999; Sagar et al., 1988). Since the homozygous mutant seedlings from three genes (OsPDS, OsZDS, and β-OsLCY) are nonviable, we generated transgenic rice plants harboring the β-OsLCY- RNAi construct. It was demonstrated that β-OsLCY- RNAi plants and Oscrtiso mutants showed a distinctly photobleached phenotype on leaves (Figure 6a,b), which was in accordance with the accumulation of ROS as revealed by nitro blue tetrazolium (NBT) staining (Figure 6c,d). Furthermore, compared with that in the wild type, higher activities of ROS-scavenging enzymes were found in both β-OsLCY-RNAi plant and phs3-1 mutant (Figure S3), suggesting that these two plants were under oxidative stress.


Mutations of genes in synthesis of the carotenoid precursors of ABA lead to pre-harvest sprouting and photo-oxidation in rice.

Fang J, Chai C, Qian Q, Li C, Tang J, Sun L, Huang Z, Guo X, Sun C, Liu M, Zhang Y, Lu Q, Wang Y, Lu C, Han B, Chen F, Cheng Z, Chu C - Plant J. (2008)

Photobleaching phenotype (a, b) and the detection of ROS (c, d) of Oscrtiso and β-LCY-RNAi plants and the corresponding wild types.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2327239&req=5

fig06: Photobleaching phenotype (a, b) and the detection of ROS (c, d) of Oscrtiso and β-LCY-RNAi plants and the corresponding wild types.
Mentions: Due to the photoprotective function of carotenoids, plants deprived of these pigments suffered from photobleaching damage, especially under high light conditions (Niyogi, 1999; Sagar et al., 1988). Since the homozygous mutant seedlings from three genes (OsPDS, OsZDS, and β-OsLCY) are nonviable, we generated transgenic rice plants harboring the β-OsLCY- RNAi construct. It was demonstrated that β-OsLCY- RNAi plants and Oscrtiso mutants showed a distinctly photobleached phenotype on leaves (Figure 6a,b), which was in accordance with the accumulation of ROS as revealed by nitro blue tetrazolium (NBT) staining (Figure 6c,d). Furthermore, compared with that in the wild type, higher activities of ROS-scavenging enzymes were found in both β-OsLCY-RNAi plant and phs3-1 mutant (Figure S3), suggesting that these two plants were under oxidative stress.

Bottom Line: Pre-harvest sprouting (PHS) or vivipary in cereals is an important agronomic trait that results in significant economic loss.As expected, the amount of ABA was reduced in all four phs mutants compared with that in the wild type.These results suggest that the impairment of carotenoid biosynthesis causes photo-oxidation and ABA-deficiency phenotypes, of which the latter is a major factor controlling the PHS trait in rice.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research, Beijing 100101, China.

ABSTRACT
Pre-harvest sprouting (PHS) or vivipary in cereals is an important agronomic trait that results in significant economic loss. A considerable number of mutations that cause PHS have been identified in several species. However, relatively few viviparous mutants in rice (Oryza sativa L.) have been reported. To explore the mechanism of PHS in rice, we carried out an extensive genetic screening and identified 12 PHS mutants (phs). Based on their phenotypes, these phs mutants were classified into three groups. Here we characterize in detail one of these groups, which contains mutations in genes encoding major enzymes of the carotenoid biosynthesis pathway, including phytoene desaturase (OsPDS), zeta-carotene desaturase (OsZDS), carotenoid isomerase (OsCRTISO) and lycopene beta-cyclase (beta-OsLCY), which are essential for the biosynthesis of carotenoid precursors of ABA. As expected, the amount of ABA was reduced in all four phs mutants compared with that in the wild type. Chlorophyll fluorescence analysis revealed the occurrence of photoinhibition in the photosystem and decreased capacity for eliminating excess energy by thermal dissipation. The greatly increased activities of reactive oxygen species (ROS) scavenging enzymes, and reduced photosystem (PS) II core proteins CP43, CP47 and D1 in leaves of the Oscrtiso/phs3-1mutant and OsLCY RNAi transgenic rice indicated that photo-oxidative damage occurred in PS II, consistent with the accumulation of ROS in these plants. These results suggest that the impairment of carotenoid biosynthesis causes photo-oxidation and ABA-deficiency phenotypes, of which the latter is a major factor controlling the PHS trait in rice.

Show MeSH
Related in: MedlinePlus