Search for an unknown mobile genetic element controlling expression of genes in phenylpropanoid biosynthesis

虽然转座因子被认为存在于几乎所有的生物中，但它们只从少数植物中分离出来，并且在遗传和分子水平上仅在玉米（Zea mays）和金鱼（Antirrhinum majus）两种植物中被表征。它们的转位、影响基因表达和促进DNA重排的能力导致遗传不稳定。我们正试图从日本的传统园艺植物中识别和表征新的转座因子，这些植物包括日本牵牛花（Pharbitisnil）、牵牛花（Ipomoea purpurea）和杜鹃花（Rhododendron）。从日本牵牛花的一个品种中，我们发现了一个6 kb的插入，称为Tpnl（转座子Pharbitis nil 1），用于花青素色素的生物合成。其末端反向重复序列和目标重复长度表明它是一个新的转座元件，属于玉米Spm/En家族。Tpnl元件的末端区域包含10bp重复序列，可能是转座酶结合位点。该区域还携带104 bp和123 bp的串联直接重复序列。假定的转座酶结合区的组织与已知的植物转座因子有很大不同。我们还发现了牵牛花中花青素生物合成基因的DNA重排，这些基因具有可变的花表型。

Although transposable elements are believed to exist in virtually every organism, they have been isolatad from only a few plants and have been characterized at genetic and molecular levels in only two plants, maize (Zea mays) and snapdragon (Antirrhinum majus). Their ability to transpose, affect gene expression and promote DNA rearrangements causes genetic instability.We are trying to identify and characterize new transposable elements from traditional horticultutral plants bearing variegated flowers in Japan which include Japanese morning glory (Pharbitisnil), morning glory (Ipomoea purpurea) and azalea (Rhododendron). From a line of the Japanese morning glory producing variegated flowers called "flecked", we have found a 6 kb insertion, termed Tpnl (Transposon Pharbitis nil one ) within the DFR gene for anthocyanin pigment biosynthesis. Its terminal inverted repeats and length of target duplications indicate that it is a new transposable element belonging to the maize Spm/En family. The terminal regions of the Tpnl element contain 10 bp repeats which are likely to be transposase binding sites. The regions also carry 104 bp and 123 bp tandem direct repeats. The organization of the putative transposase binding region differs significantly from the known plant transposable elements.We have also identified DNA rearrangements in a gene for anthocyanin biosynthesis in a line of morning glory bearing mutable flower phenotype.