The Japanese morning glory has an extensive history of genetic studies. Many mutants in the colors and shapes of its flowers and leaves have been isolated since the 17th century, and more than 200 genetic loci have been localized for the 10 linkage groups. They include over 20 mutable loci, several with variegated flower phenotypes. In a line of Japanese morning glory bearing variegated flowers called flecked, a transposable element of 6.4 kb, termed Tpn1, was found within one of the anthocyanin biosynthesis genes encoding dihydroflavonol-4-reductase (DFR). The 6.4-kb element carries 28-bp perfect terminal inverted repeats, the outer 13 bp being identical to those of the maize transposable element Suppressor-mutator/Enhancer. It is flanked by 3-bp direct repeats within the second intron of the DFR gene, 9 bp upstream of the third exon. When somatic and germinal excision occurs, it produces excision sequences characteristic of plant transposable elements. Cosegregation data of the variegated flower phenotype and the DFR gene carrying Tpn1 indicated that the mutable phenotype is due to excision of Tpn1 from the DFR gene. Sequences homologous to Tpn1 are present in multiple copies in the genome of Japanese morning glory.

Betalains are synthesized in flowers, fruits and other tissues of the plant order Caryophyllales. Betalamic acid is the chromophore of betalain pigments synthesized by a ring-cleaving enzyme reaction on l-dihydroxyphenylalanine (DOPA). Although reverse genetic evidence has proven that DOPA 4,5-dioxygenase (DOD) is a key enzyme of betalain biosynthesis, all attempts to detect recombinant plant DOD activity in vitro have failed. Here, we report on the formation of betalamic acid from DOPA under suitable assay conditions using recombinant MjDOD produced by Escherichia coli. This is the first report showing biochemical evidence for DOD activity in vitro.

cDNAs encoding an enzyme with UDP-glucose:cyclo-DOPA 5-O-glucosyltransferase activity were isolated from four o'clocks and feather cockscombs. Phylogenetic analysis of the amino acid sequences deduced from the cDNAs show that they represent a single subclade distinct from those of other phenylpropanoid and flavonoid glucosyltransferases. Changes in the amount of transcripts of the cDNA in four o'clocks correlated with the accumulation of betanin during flower development. The cDNAs isolated here were candidates for the gene of the enzyme involved in another pathway of betacyanin biosynthesis via glucosylation at the cyclo-DOPA step rather than at the betanidin step.

No abstract

The Japanese morning glory has an extensive history of genetic studies. Many mutants in the colors and shapes of its flowers and leaves have been isolated since the 17th century, and more than 200 genetic loci have been localized for the 10 linkage groups. They include over 20 mutable loci, several with variegated flower phenotypes. In a line of Japanese morning glory bearing variegated flowers called flecked, a transposable element of 6.4 kb, termed Tpn1, was found within one of the anthocyanin biosynthesis genes encoding dihydroflavonol-4-reductase (DFR). The 6.4-kb element carries 28-bp perfect terminal inverted repeats, the outer 13 bp being identical to those of the maize transposable element Suppressor-mutator/Enhancer. It is flanked by 3-bp direct repeats within the second intron of the DFR gene, 9 bp upstream of the third exon. When somatic and germinal excision occurs, it produces excision sequences characteristic of plant transposable elements. Cosegregation data of the variegated flower phenotype and the DFR gene carrying Tpn1 indicated that the mutable phenotype is due to excision of Tpn1 from the DFR gene. Sequences homologous to Tpn1 are present in multiple copies in the genome of Japanese morning glory.