Molecular Cloning, Expression And Antioxidant Effect Analysis Of A Novel Ferritin Gene CbFer In Chorispora Bungeana

Chorispora bungeana Fisch. & C.A. Mey (C. bungeana) is a rare alpine subnival plant species that is highly capable of resisting freezing environment. Lacking special morphological structure, it is an ideal plant in studying physiological and molecular mechanism in resisting freezing stress. Ferritin cDNA, CbFer, was cloned from C. bungeana. The responses of AsA-GSH system and CbFer to temperature change were examined during the course of different temperature (4℃,0℃ and -4℃) stresses, the signal transduction way of the expression of CbFer was also investigated in this paper. The special cold resistance ability of C. bungeana shows in the following aspects:1. CbFer gene is 975 bp in length with an open reading frame (ORF) of 260 amino acids, corresponding to a protein of predicted molecular mass 29.17 kDa and an isoelectric point of 5.44. The deduced amino acid sequence possesses ferritin-like diiron domain and the ferritin iron-binding regions signature.2. CbFer cDNA codes for a ferritin subunit plus a chloroplast-targeting transit peptide. RT-PCR analysis revealed that CbFer was a tissue-specfic gene, the expression could only be detected in leaves. These results suggest that the protein coded by CbFer plays function only in leaves.3. The expression patterns of CbFer gene were investigated in relation to cold stress. The CbFer gene transcript progressively increased under 4℃ and increased much more distinctly and quickly under 0℃ and -4℃. This result suggests there is a close relationship between the expression of CbFer and cold stress, CbFer expression is sensitive to low temperature. CbFer plays an important protective mechanism in signal transduction to resist cold stress in C. bungeana. Lower temperature could trigger the expression more quickly exactly, this phenomenon reflects fitly that C. bungeana has the ability to adapt to acute temperature change in the growth environment.4. The expression of CbFer was strongly inhibited by treatment with iron chelating agent Ferrozine. This result indicates that iron is a main factor in the regulating of CbFer gene expression. It was remarkable that we found cold stress could induce the expression of CbFer after Ferrozine treatment, which means there is another signal except iron induces the expression of the gene during cold stress.5. Two tested exogenous signals, excessive iron and H₂O₂, up-regulated the expression of CbFer gene. However, the expression of the gene was down-regulated...