Wakisaka Keiko Tsuji, Ichiyanagi Kenji, Ohno Seiko, Itoh Masanobu
Department of Applied Biology, Kyoto Institute of Technology, Hashigamicyo, Matsugasaki, Sakyo-ku, Kyoto, 606-8585 Japan.
Laboratory of Genome and Epigenome Dynamics, Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan.
Mob DNA. 2017 Oct 23;8:13. doi: 10.1186/s13100-017-0096-x. eCollection 2017.
Transposition of elements in the genome causes P-M hybrid dysgenesis in . For the P strain, the P-M phenotypes are associated with the ability to express a class of small RNAs, called piwi-interacting small RNAs (piRNAs), that suppress the elements in female gonads. However, little is known about the extent to which piRNAs are involved in the P-M hybrid dysgenesis in M' and Q strains, which show different abilities to regulate the elements from P strains.
To elucidate the molecular basis of the suppression of paternally inherited elements, we analyzed the mRNA and piRNA levels of elements in the F1 progeny between males of a P strain and nine-line females of M' or Q strains (M' or Q progenies). M' progenies showed the hybrid dysgenesis phenotype, while Q progenies did not. Consistently, the levels of -element mRNA in both the ovaries and F1 embryos were higher in M' progenies than in Q progenies, indicating that the M' progenies have a weaker ability to suppress -element expression. The level of -element mRNA was inversely correlated to the level of piRNAs in F1 embryos. Importantly, the M' progenies were characterized by a lower abundance of -element piRNAs in both young ovaries and F1 embryonic bodies. The Q progenies showed various levels of piRNAs in both young ovaries and F1 embryonic bodies despite all of the Q progenies suppressing -element transposition in their gonad.
Our results are consistent with an idea that the level of -element piRNAs is a determinant for dividing strain types between M' and Q and that the suppression mechanisms of transposable elements, including piRNAs, are varied between natural populations.
基因组中元件的转座会导致果蝇的P-M杂种不育。对于P品系，P-M表型与一类名为piwi相互作用小RNA（piRNA）的小RNA的表达能力相关，这类小RNA可在雌性性腺中抑制元件。然而，对于piRNA在M'和Q品系的P-M杂种不育中所涉及的程度知之甚少，M'和Q品系调节元件的能力与P品系不同。
为了阐明抑制父本遗传元件的分子基础，我们分析了P品系雄性与M'或Q品系的九系雌性（M'或Q后代）杂交产生的F1后代中元件的mRNA和piRNA水平。M'后代表现出杂种不育表型，而Q后代没有。一致地，M'后代卵巢和F1胚胎中的元件mRNA水平高于Q后代，这表明M'后代抑制元件表达的能力较弱。元件mRNA水平与F1胚胎中piRNA水平呈负相关。重要的是，M'后代的特征是在年轻卵巢和F1胚胎体中元件piRNA的丰度较低。尽管所有Q后代在其性腺中都抑制元件转座，但Q后代在年轻卵巢和F1胚胎体中都表现出不同水平的piRNA。
我们的结果与这样一种观点一致，即元件piRNA的水平是区分M'和Q品系类型的决定因素，并且包括piRNA在内的转座元件的抑制机制在自然种群之间是不同的。
