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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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The phenotypes of pre-harvest sprouting (phs) mutants in category I.The albino phenotype of phs seedlings.The pink-embryo seeds of phs4-1 and phs4-2 lines.Phenotypes of the wild type (left) and phs3-1 mutant (right) at the early tillering stage. The inset shows the magnified leaves of the wild type and phs3-1 mutant, respectively.The phs3-1 plant shows pale green over the whole leaves at the mature stage in the field.
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fig01: The phenotypes of pre-harvest sprouting (phs) mutants in category I.The albino phenotype of phs seedlings.The pink-embryo seeds of phs4-1 and phs4-2 lines.Phenotypes of the wild type (left) and phs3-1 mutant (right) at the early tillering stage. The inset shows the magnified leaves of the wild type and phs3-1 mutant, respectively.The phs3-1 plant shows pale green over the whole leaves at the mature stage in the field.

Mentions: To further characterize these mutants the viviparous seedlings were rescued, and five viviparous mutant lines showed albino seedlings (Figure 1a), these homozygous plants eventually died at about 4 weeks after germination. Interestingly, the homozygous seeds of two mutant lines among them had pink embryos (Figure 1b). Moreover, one of the viviparous mutant lines, T09, developed alternating green and yellow crossbands on the leaf blades at the tillering stage (Figure 1c), like rice zebra mutants previously described (Kusumi et al., 2000), and finally showed pale green on entire plants when mature (Figure 1d).


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)

The phenotypes of pre-harvest sprouting (phs) mutants in category I.The albino phenotype of phs seedlings.The pink-embryo seeds of phs4-1 and phs4-2 lines.Phenotypes of the wild type (left) and phs3-1 mutant (right) at the early tillering stage. The inset shows the magnified leaves of the wild type and phs3-1 mutant, respectively.The phs3-1 plant shows pale green over the whole leaves at the mature stage in the field.
© Copyright Policy
Related In: Results  -  Collection

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

fig01: The phenotypes of pre-harvest sprouting (phs) mutants in category I.The albino phenotype of phs seedlings.The pink-embryo seeds of phs4-1 and phs4-2 lines.Phenotypes of the wild type (left) and phs3-1 mutant (right) at the early tillering stage. The inset shows the magnified leaves of the wild type and phs3-1 mutant, respectively.The phs3-1 plant shows pale green over the whole leaves at the mature stage in the field.
Mentions: To further characterize these mutants the viviparous seedlings were rescued, and five viviparous mutant lines showed albino seedlings (Figure 1a), these homozygous plants eventually died at about 4 weeks after germination. Interestingly, the homozygous seeds of two mutant lines among them had pink embryos (Figure 1b). Moreover, one of the viviparous mutant lines, T09, developed alternating green and yellow crossbands on the leaf blades at the tillering stage (Figure 1c), like rice zebra mutants previously described (Kusumi et al., 2000), and finally showed pale green on entire plants when mature (Figure 1d).

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