Effect of male sterile and fertile cytoplasm on nuclear DNA methylation in hybrid rice

Abstract

Nucleus-controlled fertility restoration and cytoplasmic male sterility are important mechanisms to exploit heterosis. However, the effect of DNA methylation on cytoplasmic-nuclear interaction is not well understood yet. The current study used a methylation-sensitive amplified polymorphism to characterize polymorphism in nuclear DNA methylation among cytoplasmic male sterile line (D62A), corresponding maintainer line (D62B), and two F1 hybrids (D62A × R527 and D62B × R527). In results, 495 fragments were amplified between the parental D62A and D62B lines. The total methylation (double + single-stranded) and full methylation (double-stranded) rates of D62A (33.13%, 24.24%) both were found to be lower than that of corresponding maintainer D62B (33.94%, 24.85%). Analysis of methylation revealed that male sterile line D62A was less methylated than that of corresponding maintainer line D62B in all methylation types I, II and III. A total of 516 fragments were amplified between two F1 hybrids (D62A × R527 and D62B × R527). The total methylation in both hybrids (D62A × R527 and D62B × R527) was identical (34.69%). While full methylation rates for D62A × R527 and D62B × R527 were 25.78% and 25.58%, respectively, that is non-significant. Moreover, polymorphism in DNA methylation was found higher in F1 hybrids (5.43%) than parents (4.24%). These results implied that different cytoplasm leads to changes in nuclear DNA methylation and sterile cytoplasm has reduced the effect on nuclear methylation than non-sterile cytoplasm. Current study explains the interaction between cytoplasmic male sterility and DNA methylation which may contribute to further research.