【正文】 s dwarf phenotype. When crossed with WT, the F1 plants show the phenotype similar to Epidf, thus, Epidf is a dominant dwarf mutant. When crossed with PA64, the plant height of F1 is between two parents, and the ratio of normal to dwarf plants in F2 population is nearly to 1:3, suggesting that the mutant phenotype is controlled by one dominant nuclear gene. When Epidf was crossed with three indica varieties and three japonica varieties respectively, the plant height reduction is to %, suggesting the strong plant height reduction ability. Thus, Epidf may be used for rice intersubspecific heterosis breeding in the future.(2) The mutative gene was fine mapped within a 49kb region, whereas there was no nucleotide mutation. However, we found ORF5 (one of the seven ORFs within the mapping region) was ectopically expressed in Epidf, but silenced in WT. Considered the revertants emerged from Epidf population, we speculated that Epidf was an epigenetic mutant. By using bisulfite sequencing, we found DNA hypomethylation was occurred at 5’ region of FIE1. We also analyzed the methylation patterns of six revertants and found even FIE1 was silenced in them, DNA methylation was not recovered to the WT level, the recovered sits were enriched around the transcriptional starting site and within the third exon. We also found there were reduced H3K9me2 and increased H3K4me3 at the 5’ region of FIE1. Thus, Epidf is an unexpected epigenetic mutant, which would like to provide an intriguing opportunity to unravel epigenetic modifications for development regulation in important crop plants.(3) We discovered that FIE1 was a maternalspecific expressing gene in endosperm, which was coincided with the methylation pattern of FIE1 in tissues. The methylation level is higher in leaf, culm and young panicle than that in endosperm 6, 9 and 12 days after pollination. We also found the methylation of maternal FIE1 was much lower than that of paternal. If Epidf was used as pollen donator, the imprinting pattern was disturbed, and the methylation levels of both parental were lower. Unlike Arabidopsis, which contains only one ubiquitously expressed FIE gene, there are two FIE gene in rice, the other gene FIE2 is expressed in all the tissues. We conclude that during the genome duplication and the latter evolution, epigenetic marks may play an important role in the differentiation of the two FIE gene in rice.(4) Yeast twohybrid assay showed FIE1 interacted with rice E(z) homologs, suggesting FIE1 participates in PRC2 repression which catalyzes H3K27me3 at targets. Microarray analysis showed 305 genes were misregulated in Epidf acpanied with changed H3K27me3 levels. Thus, ectopic expression of FIE1 resulted in the mutant phenotype via abnormal distribution of H3K27me3. (5) H3K9me2 and H3K27me3 are two conserved repressive epigenetic marks in both animal and higher plants. H3K9me2 is mainly enriched in heterochromatin and functions in suppressing transposons, while H3K27me3 is mainly localized in euchromatin and provides a cellular memory to maintain the repressive state of target genes. We found there was high level of H3K9me2 at 5’ region of FIE1, whereas in Epidf, H3K9me2 was reduced and resulted in ectopic expression of FIE1 and abnormal distribution of H3K27me3. We conclude that silencing of FIE1 via H3K9me2 is essential for normal function of H3K27me3 in rice. KEY WORDS: Rice。 Dominant dwarf。 FIE1。 Epigenetic mutation。 H3K9me2。 H3K4me3縮 略 詞Abbreviations英文縮寫English abbreviations英文名稱English name中文名稱Chinese nameBERBase excision repair堿基切除修復(fù)機制ChIPChromatin Immunoprecipitation染色質(zhì)免疫共沉淀DMRsDNA demethylation regionsDNA去甲基化區(qū)域DSBsDoublestrand breaks雙鏈缺口FIEFertilization independent endosperm 不依賴受精的胚乳HATsHistone acetyltransferases組蛋白乙酰轉(zhuǎn)移酶HDACsHistone deacetylases組蛋白去乙?；窰KMTsProtein lysine methyltransferases組蛋白賴氨酸甲基轉(zhuǎn)移酶H2Aub1H2A monoubiquitionation組蛋白H2A單泛素化H3K4me3Histone3 lysine4 trimethylaiton組蛋白H3賴氨酸4三甲基化H3K9me2Histone3 lysine9 dimethylaiton組蛋白H3賴氨酸9二甲基化H3K27me3Histone3 lysine27 trimethylaiton組蛋白H3賴氨酸27三甲基化MSAPMethylationsensitice amplified polymorphism甲基化敏感擴增多態(tài)性PcGPolyb group聚梳類（蛋白）PRC2Polyb Repressive Complex 2PcG抑制復(fù)合體2PREsPolyb response elementsPRC2反應(yīng)元件PRMTsProtein arginine methyltransferases精氨酸甲基轉(zhuǎn)移酶RdDMRNAdirected DNA methylationRNA介導(dǎo)的DNA甲基化TGSTranscriptional gene silencing轉(zhuǎn)錄水平上的基因沉默UBPsUbiquitin proteases泛素蛋白酶第一章 文獻綜述隨著人口數(shù)量的日益增加和可利用耕地面積的不斷減少，提高糧食單產(chǎn)，已成為確保我國糧食安全的最重要途徑。水稻是我國最重要的糧食作物之一，在保障我國糧食安全中始終擔當著重要角色。建國以來我國的水稻單產(chǎn)經(jīng)歷了兩次質(zhì)的飛躍，第一次是20世紀50年代末60世紀初以半矮稈基因sd1的利用為標志的“綠色革命”，使高稈水稻品種變?yōu)榭沟狗陌氚捚贩N，水稻單產(chǎn)提高了2030%(Peng等，1999)；第二次是70年代三系配套的成功使水稻雜種優(yōu)勢得以有效利用，水稻單產(chǎn)又在矮稈品種的產(chǎn)量基礎(chǔ)上提高了20%（程式華，2000）。矮稈資源的合理利用是水稻株型改良的基礎(chǔ),是兩次單產(chǎn)突破的關(guān)鍵。然而進入80年代末和90年代初，我國水稻單產(chǎn)進入徘徊狀態(tài)，如何進一步提高雜交水稻的單產(chǎn)是目前最為緊迫的任務(wù)。水稻秈粳亞種間F1代表現(xiàn)強大的雜種優(yōu)勢，是進一步提高水稻單產(chǎn)的有效途徑。然而秈粳亞種間雜種表現(xiàn)株高偏高，生育期超親晚熟以及結(jié)實率偏低限制了秈粳雜種優(yōu)勢的利用(楊守仁等,1982)。因此，發(fā)掘能有效降稈并抑制F1株高超親優(yōu)勢，且對其它重要農(nóng)藝性狀影響較小的顯性矮稈基因，對水稻秈粳雜種優(yōu)勢利用和進一步提高產(chǎn)量具有重要意義。表觀遺傳調(diào)控是基因表達調(diào)控的重要組成部分，已成為當前研究的熱點。經(jīng)典遺傳學(xué)指出,基因結(jié)構(gòu)的改變會引起生物體表現(xiàn)型的改變,這種改變可以從上一代傳遞到下一代。然而生物體從祖先基因組中所獲得的并不僅僅是基因序列。在基因序列不發(fā)生變化的條件下，基因表達發(fā)生的改變也可以是遺傳的，導(dǎo)致可遺傳的表現(xiàn)型變異。這種可遺傳的表現(xiàn)型變化沒有直接涉及到基因序列的改變，因而是表觀的，稱之為表觀遺傳變異(Holliday, 1987。 Wu等, 2001。 Holliday, 2006)。研究表觀遺傳變異的遺傳學(xué)稱之為表觀遺傳學(xué)。水稻作為重要的糧食作物和模式植物，許多生物過程受表觀遺傳調(diào)控，因此在水稻中開展表觀遺傳學(xué)研究具有重要的理論和現(xiàn)實意義。1 水稻株高的研究概況 水稻矮化突變體的遺傳研究進展傳統(tǒng)水稻品種一般為高稈，矮化是水稻的突變性狀。高稈品種易倒伏，利用價值不高，矮稈水稻品種因具有較高的利用價值而研究較多。根據(jù)株高矮化的程度，廣義的矮稈又分為半矮稈、矮稈和極矮稈3種類型。狹義的矮稈通常指成熟時株高等于或低于原正常株高一半的類型；半矮稈是指株高介于矮稈和正常株高之間的矮稈類型。水稻植株矮化是由節(jié)間縮短或節(jié)間數(shù)目減少導(dǎo)致的，也有可能是兩者共同作用的結(jié)果。Takedea(1977)以節(jié)間長度占株高的比例為指數(shù)將矮稈分為dn、dm、dg、nl和sh五種類型，將節(jié)間比例正常的品種定為N型。dn類型的特征是各節(jié)間比例與N型類似；dg類型的特點是第二節(jié)間縮短；nl類型的特征是有莖葉，第一節(jié)間縮短而第四節(jié)間伸長，偶爾有第六節(jié)間伸長；dm類型的特征是第二節(jié)間特別短；sh類型的特征是第一節(jié)幾乎不伸長，穗部包在劍葉葉鞘中。除dn類型外，其余類型都存在某一特定節(jié)間的縮短，這表明不同矮化基因作用于不同的節(jié)間伸長。水稻矮稈遺傳主要有兩種類型：一類是由單基因控制的質(zhì)量性狀遺傳，另一類是由多基因控制的數(shù)量性狀遺傳。生產(chǎn)上利用的秈稻主要矮源大部分是隱性單基因遺傳，并且與sd1等位。與秈稻相比，粳稻的矮化遺傳要復(fù)雜的多，根據(jù)控制矮化的基因?qū)?shù)分為兩類：一類是受單個矮稈主效基因控制，并且這些主效基因大多不等位；另一類是受多個微效矮稈基因控制。Parnell等（1922）報道了1個由隱性單基因控制的自然矮稈突變體,這是有關(guān)水