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rearrangements of the genome (Lönnig and Saedler, 1997). Not only did Inagaki et al. (1994) establish that the observed sectoring phenotype was caused by the movement of this new transposable element, but the finding also established that, of the three DFR genes characterized, only one gene family member (DFR-B) is responsible for pigment production in the floral limb.

Another En/Spm-like element, Tpn2, has also been identified in I. nil (Hoshino and Iida, 1997b, c).§ Tpn2 is a 6.5-kb element with similarity to Tpn1. Tpn2 is inserted in the second intron of CHI in the speckled mutant. This phenotype is pale yellow with round speckles of pigment on the corolla (Abe et al., 1997). In addition to the En/Spm-like transposons, mobile element-like motifs were identified in the flanking regions of the DFR genes. These elements are similar to miniature inverted-repeat transposable elements (Hisatomi et al., 1997a; Johzuka-Hisatomi et al., 1999; Wessler et al., 1995). Mobile element-like motifs are also found in the DFR region of I. purpurea (Johzuka-Hisatomi et al., 1999) and in the CHS-D region of both I. purpurea and I. nil. Three copies of one of the elements (mobile element-like motif 6) from the CHS-D region were also found in the DFR region (Johzuka-Hisatomi et al., 1999).

Furthermore, three copies of a directly repeated sequence of about 193 bp are found at the 3′ end of the intron in CHS-D in some lines of I. purpurea (Johzuka-Hisatomi et al., 1999). Other lines of I. purpurea contain four copies of this repeat (unpublished data). In contrast, I. nil contains only one copy of this repeat, but it is interrupted by a 529-bp insertion (Johzuka-Hisatomi et al., 1999).

Another En/Spm-related element termed Tpn3 has been found in the CHS-D gene of I. nil in the r-1 mutant (Hoshino and Iida, 1999). This mutant bears white flowers with colored tubes. The insertion of this 5.57-kb element into CHS-D results in the accumulation of abnormal sizes of CHS-D mRNAs in the floral tissue (Hoshino and Iida, 1999).

A long terminal repeat retrotransposon, RTip1, has been reported associated with the ANS gene region in I. purpurea (Hisatomi et al., 1997b). The element is 12.4 kb, contains two long terminal repeat sequences of about 590 kb, and appears to be a defective Ty3 gypsy-like element. The RTip1 element resides within yet another element (MiniSip1), which is described as a minisatellite. Another minisatellite, MiniSip2, has also been described and is located within the Rtip1 element. Thus, there are three elements piggybacked on one another in the ANS 3′ flanking region. Although no phenotypic changes have been linked to these elements,

§

Hoshino, A. & Iida, S. (1997b) Genes Genet. Syst. 72, 422 (abstr.).

Hoshino, A. & Iida, S. (1999) Plant Cell Physiol. 40, Suppl., 26 (abstr.).



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