Trans-acting small RNA determines dominance relationships in Brassica self-incompatibility
Trans-acting small RNA determines dominance relationships in Brassica self-incompatibility
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DOI：
10.1038/nature09308
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发表时间：
2010-08-19
期刊：
影响因子：
64.8
通讯作者：
Takayama, Seiji
中科院分区：
文献类型：
--
作者：
Tarutani, Yoshiaki;Shiba, Hiroshi;Takayama, Seiji
二倍体生物每个基因都有两个拷贝，分别从亲本遗传一个。两个遗传等位基因的表达有时会受到显性/隐性关系的影响，这种关系决定了生物体的最终表型。为了探索这些关系背后的机制，我们研究了编码油菜自交不亲和雄性决定因素的s -座蛋白11基因（SP11）的单等位基因表达。我们之前报道过SP11在一些S杂合子中是单等位基因表达，并且隐性SP11等位基因的启动子区域在花药绒毡层中特异性甲基化（1-3）。在这里，我们表明这种甲基化是由反式作用的小非编码RNA（sRNA）控制的。我们在显性SP11等位基因的侧翼区域发现了与隐性SP11启动子相似的反向基因组序列。这些序列在花药绒毡层中特异性表达，加工成24个核苷酸的sRNA，命名为SP11甲基化诱导剂（Smi）。在隐性S纯合子中引入Smi基因组区域可触发隐性SP11等位基因启动子的甲基化，抑制其转录。这是一个例子，显示了在显性等位基因的侧翼区域编码的sRNA以反式方式诱导隐性等位基因的转录沉默。我们的发现可能为广泛存在的单等位基因表达系统提供新的见解。
A diploid organism has two copies of each gene, one inherited from each parent. The expression of two inherited alleles is sometimes biased by the effects known as dominant/recessive relationships, which determine the final phenotype of the organism. To explore the mechanisms underlying these relationships, we have examined the monoallelic expression of S-locus protein 11 genes (SP11), which encode the male determinants of self-incompatibility in Brassica. We previously reported that SP11 expression was monoallelic in some S heterozygotes, and that the promoter regions of recessive SP11 alleles were specifically methylated in the anther tapetum(1-3). Here we show that this methylation is controlled by trans-acting small non-coding RNA(sRNA). We identified inverted genomic sequences that were similar to the recessive SP11 promoters in the flanking regions of dominant SP11 alleles. These sequences were specifically expressed in the anther tapetum and processed into 24-nucleotide sRNA, named SP11 methylation inducer (Smi). Introduction of the Smi genomic region into the recessive S homozygotes triggered the methylation of the promoter of recessive SP11 alleles and repressed their transcription. This is an example showing sRNA encoded in the flanking region of a dominant allele acts in trans to induce transcriptional silencing of the recessive allele. Our finding may provide new insights into the widespread monoallelic gene expression systems.