Transposition and gene regulation of DNA transposable elements in plants

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The major DNA-based controlling transposable elements in higher plants can be classified into three groups : the Ac/Ds (or hAT) superfamily, the En/Spm (or CACTA) superfamily, and the Mu family. As floricultural plants, spontaneous mutants of the common morning glory (I. purpurea) displaying either white or reddish flowers were obtained while various spontaneous mutants of the Japanese morning glory (I. nil) exhibiting many different flower colorations were generated. We are trying to identify these spontaneous mutants including mutable alleles conferring variegated flowers. In addition, we also attempted gene targeting by homologous recombination in rice.The mutable flecked, speckled, r-1, and purple alleles in I. nil were caused by insertions of Tpn1 and its relatives in the En/Spm superfamily, Tpn2, Tpn3, and Tpn4, into the genes for anthocyanin coloration in wers, i.e., DFR-B. CHI, CHS-D, and InNHX1, respectively. Similarly, the flaked and pink mutants of I. purpurea have distantly related elements, Tip1OO and Tip201, in the Ac/Ds superfamily inserted into the CHS-D and F3'H genes, respectively. Concerning gene targeting in rice, an important staple food and a model plant for other cereal species, we have developed a large-scale Agrobacterium-mediated transformation procedure with a strong positive-negative selection and succeeded a reproducible targeting of the Waxy gene by homologous recombination without concomitant occurrence of undesirable ectopic events.