8月19日,，日本奈良尖端科學(xué)技術(shù)大學(xué)院大學(xué)的研究人員的英國《自然》（Nature）雜志上報告說，他們發(fā)現(xiàn)了動植物遺傳過程中,，顯性基因得以表達(dá),，而隱性基因表達(dá)被抑制的原因。這一發(fā)現(xiàn)將有助于對植物品種進(jìn)行改良,。
很多動植物都會將體內(nèi)的部分基因遺傳給下一代,，但是子一代在很多情況下只表達(dá)出基于一方基因的性狀（顯性性狀），而基于另一方基因的性狀（隱性性狀）則被暫時隱藏而未表現(xiàn),；在子二代中,，上述顯性基因和隱性基因都有所表達(dá)。這樣的遺傳規(guī)律被稱為“孟德爾分離定律”,。
奈良尖端科學(xué)技術(shù)大學(xué)院大學(xué)教授高山誠司和研究員樽谷芳明率領(lǐng)的小組以一種日本土生油菜為對象進(jìn)行研究,。他們發(fā)現(xiàn),，位于顯性基因附近的某種基因指導(dǎo)合成了一種低分子核糖核酸,，導(dǎo)致隱性基因甲基化，其作用從而被遏制,。研究小組推測動物也可能存在類似機(jī)制,。
高山誠司2006年曾發(fā)現(xiàn)隱性基因由于化學(xué)反應(yīng)而無法發(fā)揮作用，此次發(fā)現(xiàn)則弄清了隱性基因受到遏制的具體機(jī)制,。
高山誠司指出,，植物顯性遺傳的性狀通常是優(yōu)勢性狀。以此次發(fā)現(xiàn)為基礎(chǔ),，有可能通過人工手段,，只利用優(yōu)勢性狀對植物的品種進(jìn)行改良。（生物谷Bioon.com）
生物谷推薦原文出處：
Nature doi:10.1038/nature09308
Trans-acting small RNA determines dominance relationships in Brassica self-incompatibility
Yoshiaki Tarutani1,5, Hiroshi Shiba1, Megumi Iwano1, Tomohiro Kakizaki2,5, Go Suzuki3, Masao Watanabe4, Akira Isogai1 & Seiji Takayama1
Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma 630-0192, Japan
Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka 020-8550, Japan
Division of Natural Science, Osaka Kyoiku University, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582, Japan
Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
Present addresses: Department of Integrated Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan (Y.T.); Vegetable Breeding Research Team, National Institute of Vegetable and Tea Science, Ano, Mie 514-2392, Japan (T.K.).
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 tapetum1, 2, 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.
