Study On DNA Methylation Affected By Male Sterile Cytoplasm In Rice (Oryza Sativa L.)

Since the male sterile plants were found, especially the male sterility lines with nucleo-cytoplasmic interaction being explored, the cytoplasmic male sterile has been widely used in crop heterosis and brought great economic benefits for the world. The cytoplasmic male sterile plays an important role in three line hybrid rice, thus this field was widely researched for a long time. Previous research showed that sterile cytoplasm affected the expression of nuclear genomes, which resulted in the variation in phenotypes directly. But no reports are available on DNA methylation affected by male sterile cytoplasm in hybrid rice. In this study, four cytoplasmic male sterile lines (Jin23A、G46A、D62A and Ⅱ-32A) and the corresponding maintainer lines (Jin23B、G46B、D62B and Ⅱ-32B) were crossed with restore line R527respectively. The effects of cytoplasm to nucleoplasm on phenotype and DNA methylation were studied in this article. The results as follows:1. A line (male sterile line) and its corresponding B line (maintainer line) have the same nucleus but different cytoplasm. Both of them were crossed with the same R line (restore line). The agronomic traits of A/R and B/R were investigated. The results showed the nutrition traits of A/R such as the length/width of flag leaf and effective tillering were better than those of B/R, which was positive effect. But other traits such as heading date, the sterility, the length of panicle neck, the panicle length and seed setting rate were worse, which was negative effect.2. The biggest different traits between the A line and the corresponding B line were sterility, the length of neck-panicle, plant height and heading date. The similar differentiation appeared between A/R and corresponding B/R in above agronomic traits. This showed the R line could not make a full recovery of negative effects about sterile cytoplasm.3. Comparing the levels of methylation between sterile lines and corresponding maintainer lines, significant differences were observed in Ⅰ-type of methylation, and found the basic trend is Yinshui-type>WA-type>G-type/D-type; Some differences also existed in total methylated sites, MSAP%, full mehtylated sites and the ratio of full mehtylated sites. To I-type of methylation, all the B lines have more sites than their corresponding A lines, with the larger difference of Yinshui-type and WA-type, followed by G-type and D-type. 4.Compared the difference of the methylation levels between parents and F1s, it found that the restorer lines could influence them on the methylation levels with uncertain degree But generally, The similar differentiation appeared between parents and F1s.5.By comparing the changes of methylation polymorphisms between parents and F1s, we found, with the different cytoplasm, the different DNA methylation polymorphism occurred. It showed, although the whole methylation level was little impact by R line, The methylation polymorphism can be influenced by it obviously.