---

DNA molecules contain nitrogenous bases that look like fluorophores; however they are weakly or non-fluorescent. Hence, it is important to identify DNA binding-ligands that do not show fluorescence emission in the Free State, though their fluorescence intensity increases upon binding to DNA. Here, we report metal ions (either K and Na) induced guanine quadruplex formation with PS2.M, d (GTG3TAG3CG3T2G2), which shows peroxidase function when complexed with hemin. Ultravioletvisible absorption spectroscopy revealed activity of the PS2.M oligomer as DNAzyme, and Circular Dichroism spectroscopy showed the formation of G-quadruplex structure of PS2.M. We also studied the intrinsic fluorescence of G-quadruplex forming peroxidase-like DNAzyme. The fluorescence spectra showed increment in the intrinsic fluorescence of folded DNA in comparison with its unfolded structure of the same sequence. Moreover, unsymmetrical cyanine dye (SYBR gold) was utilized as a probe for the study of the extrinsic fluorescence of G-quadruplex DNA, where it could discriminate between the single and four-stranded structures of DNA. Also the G-quadruplex dye interaction was also investigated using Circular Dichroism and Fluorescence spectroscopies.

---

Wheat Streak Mosaic Virus (WSMV) causes extensive economic damage to wheat (Triticum aestivum L.) in many regions of the world. The present study was conducted to find out if the variations in biochemical changes in reaction to WSMV infection in F2 generation of either potentially resistant (Adl-Cross) or susceptible (Marvdasht) cultivars are genetically inherited. A factorial experiment was employed with two factors of: genotypes (Adl-Cross, Marvdasht, reistant F2s and susceptible F2s), and inoculation (either infected or non infected) at Shiraz University, Iran during 2007-2009. Leaves of seedlings were harvested at different time intervals for total protein, total phenolic compounds and peroxidase activity analysis. Results indicated that virus infection caused stress in all genotypes. Total protein reduction in the inoculated resistant Adl-Cross and in its F2s was not significant whereas it was significant in the inoculated susceptible Marvdasht and its susceptible F2s. Viral infection reduced peroxidase activity in the susceptible Marvdasht cultivar and in its susceptible F2s whereas in Adl-Cross and in its resistant F2s the activity was increased. It is speculated that peroxidase enzyme may affect synthesis of compounds effective in resistance to wheat streak mosaic virus. The trend in the increase in phenolic compounds indicated that their formation and accumulation is faster in the resistant genotypes as compared with the susceptible ones. It appears that the extent of total protein, total phenolic compounds as well as peroxidase activity changes in response to WSMV are inherited by the next generations and these biochemical changes in a genotype could be adopted as selective factors in the preliminary experimental stages of selection for tolerance to the virus.