Rice Ragged Stunt Virus Disease Development Through Regulation Of Cytokinin

Rice ragged stunt virus(RRS V) is a kind of persistent proliferating virus spreaded by brown planthopper(Nilaparvata Lugens), which belongs to the generus Oryzavirus in the family Reoviridea and can’t be transmitted by eggs. The main symptoms of RRS V-infected rice are dwarfing, increasing tillering, rotating leaf tip, ragged leaf margin and deepending leaf color.Cytokinin (CTK) plays an important role during the growth and development of plants. CTK can promote cell prolifetation and expansion, delay leaf senescence, promote chloroplast formation, induce buds, eliminate apical dominance, resistant to the virus, inhibit root elongation, regulate nutrient signal transduction, promote the formation of vascular, and increase crop production. The previrous studies had shown that the symptoms (drawfing, increasing tiller, deepending leaf color, shrinkage and twisting leaf) of RRS V-infected rice were associated with the regulation of cytokinin.Cis-zeatin-O-glycosyltransferase (cZOGT) can catalyze cis-zeatin (cZ) and cis-zeatin riboside (cZR) with biological activity into cis-zeatin-O-glucoside(cZOG) and cis-zeatin riboside-O-glycoside(cZROG) without biological activity by the way of O-glycosylation. However, this process is reversible and biological activity can be restored by deglycosylation. Therefore, this study examined the expression levels of OscZOGT genes by quantitative realtime PCR (qRT-PCR), and screened three genes (OscZOGTl,OscZOGT2and OscZOGT3) whose expression levels were significantly down-regulated in RRS V-infected rice. In order to research the function of the three genes, the interference plant expression vector targeting to OscZOGTl and OscZOGT3were respectively constructed, the overexpression plant expression vector targeting to OscZOGTl, OscZOGT2and OscZOGT3were respectively constructed. Then these vectors were transfered into rice callus by Agrobacterium-mediated method, and the phenotypes in To generation of transgenic rice were observed. There were transgenic rice with the interference plant expression vector targeting to OscZOGTl and the overexpression plant expression vector targeting to OscZOGT2. The phenotypes of transgenic rice with the interference plant expression vector targeting to OscZOGT1were shrinkage and twisting. The expression level of OscZOGTl in transgenic rice with the interference plant expression vector targeting to OscZOGT1was only7.15%of that in transgenic rice with pXQact. The phenotypes of transgenic rice with the overexpression plant expression vector targeting to OscZOGT2were that leaf base angle was bigger than that in transgenic rice with pXQact, and shorter than that in transgenic rice with pXQact. The expression level of OscZOGT2in transgenic rice with the overexpression plant expression vector targeting to OscZOGT2is171times as much as that in transgenic rice with pXQact.The amount of cytokinins in healthy and RRSV-infected Nipponbare rice were detected. The results indicated that the amount of cytokinins in RRSV-infected Nipponbare rice was much more than that in healthy Nipponbare rice, which was associated with the phynotypes (increasing tilling, deepending leaf color, dwarfing) in RRSV-infected rice.