The Functional Study Of Arabidopsis Thaliana DOS1/CE01 And CE02 In Stress Responses

The Arabidopsis cDNA of CEO1, enhances the tolerance to oxidative stress in Yap1- and wild-type yeast, and modulates ABA, ethylene and methyl jasmonate responses in Arabisopsis. Here we isolated and characterized Arabidposis T-DNA insertion mutants of AT1g32230 and AT2g35510(dos1-1/ceo1-1,ceo2-1).Further phenotype analysis of dos1-1 has exhibited several distinctive phenotypes, including smaller, altered leaf shape, and more erect rosettes. While ceo2-1 mutants have no obvious difference with WT under normal condition .The dos1-1 mutantsin are hypersensitive to H₂O₂ and HgCl₂ in seed germination, seedling growth, and chlorophyll synthesis. The dos1-1 mutantsin are hypersensitive to mannitol (a non-pentrating osmolyte that mimics drought stress) in seeding growth. Interestingly, HgCl₂ could strongly induce H₂O₂ production in dos1-1 plants. We investigated whether abiotic stresses such as drought, H₂O₂, or HgCl₂ induced DOS1 gene expression by RT-PCR analysis. The data indicated that all the examined stress conditions induced marked accumulation of mRNAs for the DOS1 gene. We compared the transcription of H₂O₂, drought and HgCl₂ responsive genes in WT and dos1-1 mutant plants. It was found that The transcripts of CAT1 gene were found at similar levels in the wild-type and dos1-1plants with or without treatment of H₂O₂, drought and HgCl₂. CAT3 gene were found lower in dos1-1 than wild-type plants with treatment of H₂O₂. Interestingly, CAT2 gene transcript levels under H₂O₂ and drought stress were lower in dos1-1plants as compared to wild-type Arabidopsis. A little bit inhibition of CAT2 gene transcription in dos1-1 plants was also found following HgCl₂ treatment. The transcripts of APX1 gene were found at similar levels in the wild-type and dos1-1plants with or without treatment of H₂O₂, drought and HgCl₂. RD28, another the major intrinsic protein (MIP) homolog, was demonstrated to be aquaporin in plasma membranes. The deficient of DOS1 gene did not affect the transcription of RD28 gene. However, the RD28 gene transcripts were lower levels in dos1-1under drought or HgCl₂ stress but not under H₂O₂ treatment. This indicates that RD28 gene expression is more sensitive to drought and heavy metal stresses in dos1-1mutant and implies that water channel plays an important role in both drought and heavy metal stress damage. Thus, these results suggest that the Arabidopsis DOS1 acts as a common molecular switch , which mediates the H₂O₂ and drought stress signaling and confers heavy metal mercury tolerance. CEO2 gene may have a role in both drought and heavy metal stress damage. The ceo2-1 mutantsin are sensitive to HgCl2 in seedling growth, so CEO2 gene is a regulator in heavy metal stress damage. Moreover, ceo2-1 showed the water transpiration insensitive phenotype, so CEO2 gene is a negative regulator in drought damage.CEO1 gene belongs to a small multigene family of Arabidopsis composed of at lease five members. CEO2 gene is probably a close homologue of CEO1 gene. But The dos1-1 are hypersensitive to drought in seedling growth, and ceo2-1 are insensitive to drought in seedling growth. The functional relationship between DOS1 gene and CEO2 gene may have overlapping, but distinguishable, biological functions. CEO2 gene expressed more in younger leaves and the end of roots and less in older leaves.Metabolism in younger leaves and the end of roots is more activity,but Metabolism in older leaves is less activity.These result suggest that CEO2 gene has a important role in Arabidopsis.