Further Functional Studies About SsPrxQ Gene And AtPrxQ Gene

Cell metabolism and many stresses unavoidably produce reactive redox intermediates.ROS can act as signals controlling and regulating many biological processes, such asgrowth, cell cycle, programmed cycle, programmed cell death, hormone signaling,biotic and abiotic stress responses and development. But excessive ROS can causeserious damage to macromolecules such as proteins, lipids, or nucleic acids, eventuallyleading to extensive cell injury or death. For this, the reactivity of oxygen has to becontrolled to maintain the cellular metabolism in a functional state.An efficient antioxidant network is essential for the maintenance of cell functions,particularly in the context of mitochondrial and chloroplast metabolism. Metabolitessuch as glutathione and ascorbate and enzymes such as superoxide dismutase (SOD),ascorbate peroxidase (APX) and glutathione peroxidase are acknowledged elements ofantioxidant metabolism. Recently, peroxiredoxins (Prxs) have been identified as a newclass of enzymatic antioxidants. They function in thiol-dependent reduction of hydrogenperoxide (H₂O₂), alkyl hydroperoxides and peroxynitrite. Peroxiredoxins are ubiquitous,abundant and versatile. Within the plant peroxiredoxins, four clusters of related proteinsare distinguished: 1-Cys Prx, 2-Cys Prx, Typeâ…¡Prx and Prx Q. Prx Q, as representativeof the fourth subgroup, was identified initially in Sedum linear as a homologue ofEscherichis coli bacterioferritin co-migratory protein (BCP). Although, the molecularand biochemical characterization of Prxs genes in plants is advancing rapidly, however,data on the Prx Q in plants still remain scarce.Our laboratory cloned a peroxiredoxin Q gene from a 400mM NaCl-treated cDNAlibrary of Suaeda salsa L. and proved that this gene was a stress response gene and hadan important role in improving stresses tolerance of Arabidopsis. Here, we analyzed thesubcellular localization of SsPrxQ gene by transgenic Arabidopsis expressingSsPrxQ-pYFP. Our results proved the SsPrxQ protein localizes in chloroplast, which isconsistent with program Chlorop1.1 analysis result: that the N-terminus 64 amino acidsconstitute the chloroplast transit peptide. For further functional study about Ss Prx Qprotein and a functional comparison with At Prx Q protein, we constructed four yeastvectors:p416+ Ss Prx Q, p426+ Ss Prx Q, p416+At Prx Q, p426+ At Prx Q. Weanalyzed yeasts overexpressing Ss Prx Q genes or At Prx Q genes under NaCl, KCl,high temperature, low temperature, H2O2 conditions, and the results suggested that AtPrx Q genes carried by low copied vector(p416)more improved stresses tolerance ofyeast. In addition, RNAi of At Prx Q in Arabidopsis have been carried on by using thetechnique of post-transcriptional gene silence (PTGS). RNAi vector At Prx Q-pGSA1252 was constructed, then the vector was introduced into Arabidopsis by floraldipping method. Transformants were screened by using herbicide Finale and havegotten Basta-resistance plants of the gene silence of Prx Q in Arabidopsis. Two ofBasta-resistance plants of the gene silence of Prx Q have been confirmed by PCR. Thefurther molecular identification of these Basta-resistance plants is going on.