Using Two Molecular Markers Of Rapd And Issr Technology Research Zizania Dna Introgression And Tissue Culture Process Induced In The Rice Genome Variation And Epigenetic Variation

Wide hybridization plays an important role in plant species evolution, and one that often leads to new speciation, either through polyploidization or at the diploid level. Recent studies showed that wide hybridization is often accompanied by an array of genetic and epigenetic changes.Zizania latifolia(Griseb.) Turcz ex Stapf is a perennial wild rice in the tribe of Oryzeae, and thus related to cultivated rice (Oryza sativa L.). Over the years, our laboratory has found that Zizania DNA introgression could induce a large number of genetic and epigenetic changes of the rice genome. In this thesis, we employed two DNA markers, RAPD and ISSR, to further study the genetic and epigenetic changes that are induced by Zizania latifolia DNA introgressin or tissue culture. The following results were generalized: (1) Sequence changes and methylation alterations are frequent in the introgression lines; (2) The similarity of Tong35 and parent Songqian is higher than RZ-2 and Songqian; (3) Changes induced by tissue culture are mostly epigenetic. One kind of methylation alterations is that the unmethylated CCGG sequence was transformed into external hemimethylated cytosines. This type change, however, did not transmit to progenies of the plant. Another kind of methylation alterations is tissue culture-induced occurrence of de novo methylation at the external cytosines of the CCGG sites that are originally with hyper-methylated internal cytosines. Interestingly, many of these methylated external cytosines became demethylated again upon plant regeneration, implying that the hypomethylated state of these loci is required for successful plant regeneration. Because the changed methylation patterns are highly similar among calli subcultured for different intervals, and because apparent concordance exists between randomly selected individual regenerants, we are tempted to deduce that the DNA methylation changes did not occur randomly, rather, the methylation events likely to have hot spots, and/or occur non-randomly. Sequence analysis indicates that the loci underwent methylation alterations are predominantly genie, sharing significanthomology to known-function genes or EST sequences. This finding implies that the epigenetic changes induced by tissue culture could potentially affect expression of the relevant genes.