Os03g0125100

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The gene Os03g0125100 (LOC_Os03g03370) was reported as DSM2 in 2009. It encodes a putative BCH (named DSM2/OsBCH1) belonging to the BCH family[1]. This gene was also named OsHYD3[2].

Annotated Information

Function

The rice DSM2 gene significantly contributes to control of the xanthophyll cycle and ABA synthesis, both of which play critical roles in the establishment of drought resistance in rice.'[1].
GO assignment(s): GO:0003824,GO:0008152

Mutation

  • dsm2-1 and dsm2-2[1]:
    • The T-DNA insertion sites of dsm2-1 and dsm2-2 are located in the third intron and the first exon, respectively.
    • The reduced yield and biomass of dsm2-1 may be partially due to the reduced root growth, pollen fertility, and photosynthesis rate under drought stress.
    • The amounts of zeaxanthin and ABA were significantly reduced in two allelic dsm2 mutants after drought stress compared with the wild type.
    • Under drought stress conditions, the mutant leaves lost water faster than the wild type and the photosynthesis rate, biomass, and grain yield were significantly reduced, whereas malondialdehyde level and stomata aperture were increased in the mutant.
    • The mutant is also hypersensitive to oxidative stresses.
    • The mutant had significantly lower maximal efficiency' of photosystem II photochemistry and nonphotochemical quenching capacity than the wild type, indicating photoinhibition in photosystem II and decreased capacity for eliminating excess energy by thermal dissipation.
    • Compared with the wild type, the SOD activity in the mutant was slightly higher before the stress but was significantly reduced after the stress.
  • transgenic lines[1]:
    • Three positive transgenic lines:
      • O11
      • O13
      • O17
    • three negative transgenic lines:
      • O2
      • O3
      • O4
    • They were tested for drought resistance at the four-leaf stage in barrels and at the reproductive stage in PVC tubes.
    • After drought treatments at the reproductive stage, the overexpression lines had more green leaves and higher spikelet fertility than negative transgenic lines. The overexpression lines had less oxidative damage on the leaves and higher seed-setting rates than the negative control.

Expression

  • Overexpression of DSM2 in rice resulted in significantly increased resistance to drought and oxidative stresses and increases of the xanthophylls and nonphotochemical quenching. Some stress-related ABA responsive genes were up-regulated in the overexpression line[1].
  • Transcript analysis suggested that the expression of DSM2 was abolished in the two allelic dsm2 mutants. The DSM2 transcript level was induced (7- to 9-fold) by drought and salt treatments and slightly induced by ABA. However, DSM2 was not induced by the other treatments (and was slightly suppressed by cold stress)[1].
  • A strong GFP signal was observed in the stamen, plumule, hull, pistil,mature leaf, and root, and a weak GFP signal was detected in calli, young shoot and root, and endosperm, suggesting an organ/ tissue-dependent differential expression pattern of DSM2 in rice[1].

Evolution

In the rice genome, there are two homologs of DSM2/ OsBCH1, designated OsBCH2 (LOC_Os04g48880) and OsBCH3 (LOC_Os10g38940), showing 82% and 75% identity to OsBCH1, respectively. DSM2 belongs to the BCH family[1].

Knowledge Extension

  • The CYP97 and BCH gene pairs are primarily responsible for hydroxylation of α- and β-carotenes, respectively, but exhibit some overlapping activities, most notably in hydroxylation of the β-ring of α-carotene. The BCH duplicates encode isozymes that show significant expression divergence in reproductive organs[3].
  • The two BCH isozymes could hydroxylate the β-ring of α-carotene, though again to a lower extent than the full four enzyme complement in the wild type[3].

Labs working on this gene

  • National Key Laboratory of Crop Genetic Improvement, National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan 430070, China

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Du H, Wang N, Cui F, et al. Characterization of the β-carotene hydroxylase gene DSM2 conferring drought and oxidative stress resistance by increasing xanthophylls and abscisic acid synthesis in rice[J]. Plant Physiology, 2010, 154(3): 1304-1318.
  2. Vallabhaneni R, Gallagher C E, Licciardello N, et al. Metabolite sorting of a germplasm collection reveals the hydroxylase3 locus as a new target for maize provitamin A biofortification[J]. Plant physiology, 2009, 151(3): 1635-1645.
  3. 3.0 3.1 Kim J, Smith J J, Tian L, et al. The evolution and function of carotenoid hydroxylases in Arabidopsis[J]. Plant and cell physiology, 2009, 50(3): 463-479.

Structured Information