Activation of a rice endogenous retrotransposon Tos17 in tissue culture is accompanied by cytosine demethylation and causes heritable alteration in methylation pattern of flanking genomic regions
Activation of a rice endogenous retrotransposon Tos17 in tissue culture is accompanied by cytosine demethylation and causes heritable alteration in methylation pattern of flanking genomic regions
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DOI：
10.1007/s00122-004-1618-8
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发表时间：
2004-06-01
影响因子：
5.4
通讯作者：
Liu, B
中科院分区：
文献类型：
--
作者：
Liu, ZL;Han, FP;Liu, B
Tos 17是一个类似copia的水稻隐性反转录转座子，但可以通过组织培养激活。为了研究控制Tos 17活性的可能的表观遗传机制，我们将三个水稻品系（亲本品系cv. Matsumae和两个基因渗入系RZ 2和RZ 35），携带不同拷贝的元件组织培养。对于每个系，我们研究了Tos 17在种子植物，愈伤组织和再生植物中的转录和转座，Tos 17内CG和CNG位置的胞嘧啶甲基化状态，5-氮杂胞苷对Tos 17甲基化状态和活性的影响，以及Tos 17在愈伤组织和再生植物中的原始和一些新转座拷贝侧翼基因组区域的胞嘧啶甲基化状态。我们发现只有在导入系RZ 35中Tos 17被转录激活并被组织培养暂时动员，随后在植株再生之前或之后被阻遏。RZ 35愈伤组织和再生植株中Tos 17的活性和失活分别伴随着元件内的低CG甲基化和高CG甲基化以及半CNG甲基化和完全CNG甲基化，而其他两个系中元件的固定化伴随着接近恒定的完全高甲基化。用5-氮杂胞苷处理诱导CG和CNG在两个系（Matsumae和RZ 35）中Tos 17的部分低甲基化，然而，这并不伴随着Tos 17在任何系中的激活。胞嘧啶甲基化模式的遗传改变发生在RZ 35愈伤组织和再生植株中Tos 17侧翼的7个基因组区域中的3个中，但在另外两个系中Tos 17侧翼的5个区域中没有发生。
Tos17 is a copia-like, cryptic retrotransposon of rice, but can be activated by tissue culture. To study possible epigenetic mechanism controlling activity of Tos17, we subjected three rice lines (the parental line cv. Matsumae and two introgression lines, RZ2 and RZ35) that harbor different copies of the element to tissue culture. For each line, we investigated transcription and transposition of Tos17 in seed plants, calli and regenerated plants, cytosine-methylation status at CG and CNG positions within Tos17, effect of 5-azacytidine on methylation status and activity of Tos17, and cytosine-methylation states in genomic regions flanking original and some newly transposed copies of Tos17 in calli and regenerated plants. We found that only in introgression line RZ35 wasTos17 transcriptionally activated and temporarily mobilized by tissue culture, which was followed by repression before or upon plant regeneration. The activity and inactivity of Tos17 in calli and regenerated plants of RZ35 are accompanied by hypo- and hyper-CG methylation and hemi- and full CNG methylation, respectively, within the element, whereas immobilization of the element in the other two lines is concomitant with near-constant, full hypermethylation. Treatment with 5-azacytidine induced both CG and CNG partial hypomethylation of Tos17 in two lines (Matsumae and RZ35), which, however, was not accompanied by activation of Tos17 in any line. Heritable alteration in cytosine-methylation patterns occurred in three of seven genomic regions flanking Tos17 in calli and regenerated plants of RZ35, but in none of the five regions flanking dormant Tos17 in the other two lines.