摘要
Eighteen pairs of diploid-haploid twin-seedlings were identified and screened out fromspecial rice SARII-628 population. Five pairs of themwere selected and randomly designated as A, B, C, Dand E. Simple sequence repeats (SSR) analysisshowed that there was no difference among 310 siteswhich indicated that there was no base mutation onDNA primary structure. DNA methylation plays animportant role in gene expression regulation duringgrowth and development stages in eukaryotes. Amodified AFLP technique (methylation-sensitiveAFLP, MSAP) was employed to detect the DNA me-thylation patterns in the 5′-CCGG sites of the fivepairs of twin-seedlings. Although no methylationmutation was detected among the five diploids,forty-three methylation mutation sites were foundfrom the corresponding haploids. The MSAP ratios,which were the ratios of MSAP sites to the total am-plified sites, in five haploids were 18.79%, 19.35%,18.49%, 18.45% and 18.75%, respectively. And cor-responding full methylation levels (5′-CmCGG indouble strands) of those haploids were 10.58%,11.3%, 10.11%, 10.09% and 10.34%, respectively.Both MSAP and full methylation levels in the fivehaploids were higher than that of their correspondingdiploids, which suggested that hypermethylation oc-curred in some 5′-CCGG sites. Five types of MASPpatterns among the five pairs of twin-seedlings weredetected as follows: (1) no changes, methylation lev-els were the same in both haploids and diploids; (2) demethylation, diploid was methylated but no me-thylation in the same site in haploid; (3) hypermethy-lation, the methylation level in haploid was higher than those in diploid; (4) hypomethylation, methyla-tion in haploid was lower than those in diploid; (5) undecided pattern, change trend of methylation lev-els in haploids was not decided. The bands of 18 sites were reclaimed, then sequenced and searched on website to determine the sites of those sequences on rice chromosomes. The result showed that the methylation mutation involved the whole rice genome and 12 pairs of chromosomes. The mutation was site-related and there were different mutation sites for different haploids. Compared to diploids, the higher methylation level in haploids might be a readjusting reaction to the decrease in ploidy for the sake of sur-vival.
Eighteen pairs of diploid-haploid twinseedlings were identified and screened out from special rice SARII-628 population. Five pairs of them were selected and randomly designated as A, B, C, D and E. Simple sequence repeats （SSR） analysis showed that there was no difference among 310 sites, which indicated that there was no base mutation on DNA primary structure. DNA methylation plays an important role in gene expression regulation during growth and development stages in eukaryotes. A modified AFLP technique （methylation-sensitive AFLP, MSAP） was employed to detect the DNA methylation patterns in the 5＇-CCGG sites of the five pairs of twin-seedlings. Although no methylation mutation was detected among the five diploids, forty-three methylation mutation sites were found from the corresponding haploids. The MSAP ratios, which were the ratios of MSAP sites to the total amplified sites, in five haploids were 18.79%, 19.35%, 18.49%, 18.45% and 18.75%, respectively. And corresponding full methylation levels （5＇-crnCGG in double strands） of those haploids were 10.58%, 11.3%, 10.11%, 10.09% and 10.34%, respectively. Both MSAP and full methylation levels in the five haploids were higher than that of their corresponding diploids, which suggested that hypermethylation occurred in some 5＇-CCGG sites. Five types of MASP patterns among the five pairs of twin-seedlings were detected as follows： （1） no changes, methylation levels were the same in both haploids and diploids; （2） demethylation, diploid was methylated but no methylation in the same site in haploid; （3） hypermethylation, the methylation level in haploid was higher than those in diploid; （4） hypomethylation, methylation in haploid was lower than those in diploid; （5） undecided pattern, change trend of methylation levels in haploids was not decided. The bands of 18 sites were reclaimed, then sequenced and searched on website to determine the sites of those sequences on rice chromosomes. The result showed that the methylation mutation involved the whole rice genome and 12 pairs of chromosomes. The mutation was site-related and there were different mutation sites for different haploids. Compared to diploids, the higher methylation level in haploids might be a readjusting reaction to the decrease in ploidy for the sake of survival.
