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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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ABA content and water loss assay of phs mutants and wild types. (a) ABA content in wild-type and mutant seedlings. (b) Water loss assays for the leaves of the wild type and Oscrtiso mutant (T09/phs3-1) were performed within 120 min. Standard deviations were obtained from five measurements.
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fig09: ABA content and water loss assay of phs mutants and wild types. (a) ABA content in wild-type and mutant seedlings. (b) Water loss assays for the leaves of the wild type and Oscrtiso mutant (T09/phs3-1) were performed within 120 min. Standard deviations were obtained from five measurements.

Mentions: To investigate whether the reduced level of carotenoids in phs mutants causes a decreased level of ABA we measured the ABA content in the respective phs mutants by immunoassay. As shown in Figure 9a, the amount of ABA was reduced in all four mutants, but much more significantly in Ospds, Oszds, and Oslcy mutants compared with that in the wild type. Since ABA is also directly involved in the regulation of stomatal aperture, we examined the water loss characteristics of phs3-1/Oscrtiso plants. Wild-type and mutant plants were grown in the soil under a normal irrigation regime. The water loss analysis was carried out at the tillering stage, and the results revealed a water loss of about 53% of fresh weight within 120 min in phs mutants, whereas wild-type leaves showed only a 38% loss, indicating that the rate of water loss in phs mutants was faster than in wild-type plants (Figure 9b).


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)

ABA content and water loss assay of phs mutants and wild types. (a) ABA content in wild-type and mutant seedlings. (b) Water loss assays for the leaves of the wild type and Oscrtiso mutant (T09/phs3-1) were performed within 120 min. Standard deviations were obtained from five measurements.
© Copyright Policy
Related In: Results  -  Collection

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

fig09: ABA content and water loss assay of phs mutants and wild types. (a) ABA content in wild-type and mutant seedlings. (b) Water loss assays for the leaves of the wild type and Oscrtiso mutant (T09/phs3-1) were performed within 120 min. Standard deviations were obtained from five measurements.
Mentions: To investigate whether the reduced level of carotenoids in phs mutants causes a decreased level of ABA we measured the ABA content in the respective phs mutants by immunoassay. As shown in Figure 9a, the amount of ABA was reduced in all four mutants, but much more significantly in Ospds, Oszds, and Oslcy mutants compared with that in the wild type. Since ABA is also directly involved in the regulation of stomatal aperture, we examined the water loss characteristics of phs3-1/Oscrtiso plants. Wild-type and mutant plants were grown in the soil under a normal irrigation regime. The water loss analysis was carried out at the tillering stage, and the results revealed a water loss of about 53% of fresh weight within 120 min in phs mutants, whereas wild-type leaves showed only a 38% loss, indicating that the rate of water loss in phs mutants was faster than in wild-type plants (Figure 9b).

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