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

尽管转座因子被认为存在于几乎每种生物体中，但它们仅从少数植物中分离出来，并且仅在两种植物（玉米（Zea mays）和金鱼草（Antirrhinum majus））中在遗传和分子水平上进行了表征。转座因子具有转座、影响基因表达和促进DNA重排的能力，这导致了遗传的不稳定性。我们试图从日本传统的具有杂色花的园艺植物中鉴定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）。从日本牵牛花生产杂色花称为“斑点”的线，我们已经发现了一个6 kb的插入，称为Tpnl（转座子牵牛花色素合成的DFR基因内）。其末端反向重复序列和靶重复序列的长度表明它是一个新的转座因子，属于玉米Spm/En家族。Tpnl元件的末端区域含有10 bp重复序列，其可能是转座酶结合位点。该区域还携带104 bp和123 bp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元件显著不同。我们还在一株具有突变花表型的牵牛花中鉴定了花色素苷生物合成基因的DNA重排。

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.