The Physiological And Epigenetic Variation Induced By Heavy Metal Stress In Different Genotypes Of Rice

Heavy metal can be toxic to plants,and plants have emerged some mechanisms to endure heavy metal stress during the long-term evolvement process.Some studies indicate that the variation of DNA methylation and gene expression on specific sequences can be induced by heavy metal stress in rice.Moreover,heavy metal can effect a series of physical indexes in response to stress.This work adopted 4 types heavy metal(Cu?Cr?Cd?Hg)with a relative low concentration and high concentration to cultivate 3 different genotypes rice RZ-1?RZ-2 and T-35.After 7 days with heavy metal stress,measured their physical indexes,analyzed the variation of DNA methylation by Southern Blot and detected gene expression status of specific sequences by RT-PCR and Real-time PCR.In this study,18 physical indexes were measured,including plant height,root length,the aboveground and underground fresh weight,chlorophyll content,ion content,osmotic adjustment substances(proline and soluble sugar),antioxidase and so on.The results show that these 3 types of rice have different tolerance in physical aspect under heavy metal stress,and T-35 presents the most significant tolerance,RZ-2 takes second,RZ-1 is the most sensitive one.The DNA methylation analysis domesticates that alterations are predominant CHG hypomethylation events in T-35,while there are a lot of hypermethylation events can be observed in RZ-1 and RZ-2.Gene expression patterns of some relative enzymes in RdDM pathway indicate that the variation of the genes expression in T-35 is different from RZ-1 and RZ-2.Thus the consequences of this part illustrate that the changes of these genes are relevant to the different variation tendency on DNA methylation.This thesis analyzes the responses of various genotypes rice suffered with different concentration of different types heavy metals from physical indexes and epigenetics aspects.Luckily,an identical result is observed,which is T-35 performs more prominent tolerance.And this consequence seems provide a new evidence that T-35 can be planted widely compared with RZ-1 and RZ-2.In addition,this work also can offer some theoretical basis on the mechanisms of heavy metal tolerance and breeding new heavy metal-resistant varieties.