| Formaldehyde (HCHO) is a highly reactive compound and has a toxic effect on all organisms through its nonspecific reactivity with nucleic acid, protein, and lipid. In recent years, new materials with artificial lumbers have been used more and more for architectures and ornaments and the fitments. This makes HCHO become one of the main indoor air pollutants. Using both physiological methods and chemical methods to remove HCHO in indoor environment have some limitations and oxidants can make the secondary pollutions. If we can use indoor ornamental plants to clear and absorb formaldehyde, it will be the most simple, economic and environmental method.Ivy (Hedera helix) is a kind of evergreen and woodiness liana plants. It has not only a very strong ability to adapt to environment but also fragrance and beautiful shape. Thus ivy is often placed indoor as ornamental plants. In this research we use the leaves of Ivy as the study materials. The ability of Ivy to absorb liquid and gaseous HCHO was determined. 13C-HCHO trace experiment was performed to clarify the HCHO metabolic pathway in ivy leaves. The results showed that ivy could absorb liquid and gaseous HCHO. The absorbed 13C-HCHO was metabolized into methanol and then sugars.The amino acid contents in the ivy leaves treated with formaldehyde for 2h,12h and 24h,respectively, were determined. The results showed that the contents of Ser, Cys had no change compared with the control in the whole treatment period while the contents of Glu, Gly, His, Trp, Phe and Ala had fallen to zero at 24h. The analysis for the contents of total protein, soluble sugar and MDA (malondialdehyde) in the leaves of Ivy stressed with 2 mM and 4 mM HCHO showed that the contents of total protein, soluble sugar and MDA displayed an increase trends after treated with 2 mM HCHO. This suggested that HCHO treatment caused oxidative stress and changes in genes expression. To further analysis HCHO stress induced genes in ivy leaves, the suppression subtractive hybridization (SSH) method was used to construct a forward SSH cDNA library consisting of 912 clones for leaves stressed with 2 mM HCHO.578 positive clones were detected from the SSH cDNA library by PCR analysis.238 clones with insert≥300bp were selected for sequence analysis and 183 ESTs were obtained. Of the 183 ESTs,163 ESTs are non-redundant sequences including 58% known function sequences and 40% unknown sequences as well as 2% new ESTs. The 58% known function sequences were categorized as transcript and signal transduction (14), defense and cell death (14), metabolism (26), protein metabolism (5), energy (3), cell structure and growth (5), photosynthesis (26) as well as transport (1). Expression profiling analysis for the selected 20 genes with RT-PCR confirmed that the genes encoding xyloglucan endotransglucosylase, light-harvesting protein, 1-deoxy-D-xylulose-5-phosphate synthase, acetyl-CoA carboxylase, isocitrate lyase, NADPH:protochlorophyllide oxidoreductase, ribulose-5-phosphate epimerase,1-deoxyxylulose-5-phosphate synthase, plastocyanin b, Auxin-responsive protein IAA27 and microsomal omega-6 fatty acid desaturase were up-regulated.These results established the bases for further study on molecular mechanism of ivy in responsive to HCHO stress and provide important clues for formaldehyde metabolic engineering in transgenic plants. |
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