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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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Hormone contents and expression of hormone-regulated genes. (a) ABA and GA content in wild-type and β-Oslcy seeds at 30 days after pollination (DAP). (b) Expression of rab16B (LEA protein gene), TRAB1 (a bZIP factor gene) and RAmy1A (α-amylase gene) genes in wild-type and β-Oslcy seeds at 30 DAP.
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fig10: Hormone contents and expression of hormone-regulated genes. (a) ABA and GA content in wild-type and β-Oslcy seeds at 30 days after pollination (DAP). (b) Expression of rab16B (LEA protein gene), TRAB1 (a bZIP factor gene) and RAmy1A (α-amylase gene) genes in wild-type and β-Oslcy seeds at 30 DAP.

Mentions: Abscisic acid and another important phytohormone, GA, which can directly antagonize ABA signaling during induction of dormancy, are two important regulators of seed dormancy. Therefore, we measured the ABA and GA content in homozygous phs4-1/β-Oslcy seeds 30 DAP (phs4 homozygous seeds were easily discernible by their pink embryo). As expected, the ABA level in phs4-1/β-Oslcy was lower than that in the wild type; however, GA in phs4-1/β-Oslcy is higher than that in the wild type (Figure 10a). We further examined the expression of two ABA-regulated genes, rab16B and TRAB1, as well as a GA-induced gene, the α-amylase gene RAmy1A (AK073487), which were involved in embryo development and seed maturation (Hobo et al., 1999; Mitsui et al., 1996; O'Neill et al., 1990; Ono et al., 1996). The results demonstrated that the transcripts of rab16B and TRAB1 were significantly reduced in phs4-1/β-Oslcy seeds while the transcript of RAmy1A was increased (Figure 10b), suggesting that the ABA/GA ratio in phs4-1/β-Oslcy seeds is probably a switch for PHS.


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)

Hormone contents and expression of hormone-regulated genes. (a) ABA and GA content in wild-type and β-Oslcy seeds at 30 days after pollination (DAP). (b) Expression of rab16B (LEA protein gene), TRAB1 (a bZIP factor gene) and RAmy1A (α-amylase gene) genes in wild-type and β-Oslcy seeds at 30 DAP.
© Copyright Policy
Related In: Results  -  Collection

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

fig10: Hormone contents and expression of hormone-regulated genes. (a) ABA and GA content in wild-type and β-Oslcy seeds at 30 days after pollination (DAP). (b) Expression of rab16B (LEA protein gene), TRAB1 (a bZIP factor gene) and RAmy1A (α-amylase gene) genes in wild-type and β-Oslcy seeds at 30 DAP.
Mentions: Abscisic acid and another important phytohormone, GA, which can directly antagonize ABA signaling during induction of dormancy, are two important regulators of seed dormancy. Therefore, we measured the ABA and GA content in homozygous phs4-1/β-Oslcy seeds 30 DAP (phs4 homozygous seeds were easily discernible by their pink embryo). As expected, the ABA level in phs4-1/β-Oslcy was lower than that in the wild type; however, GA in phs4-1/β-Oslcy is higher than that in the wild type (Figure 10a). We further examined the expression of two ABA-regulated genes, rab16B and TRAB1, as well as a GA-induced gene, the α-amylase gene RAmy1A (AK073487), which were involved in embryo development and seed maturation (Hobo et al., 1999; Mitsui et al., 1996; O'Neill et al., 1990; Ono et al., 1996). The results demonstrated that the transcripts of rab16B and TRAB1 were significantly reduced in phs4-1/β-Oslcy seeds while the transcript of RAmy1A was increased (Figure 10b), suggesting that the ABA/GA ratio in phs4-1/β-Oslcy seeds is probably a switch for PHS.

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