F. Brugliera et al., ISOLATION AND CHARACTERIZATION OF A CDNA CLONE CORRESPONDING TO THE RT LOCUS OF PETUNIA-HYBRIDA, Plant journal, 5(1), 1994, pp. 81-92
We have isolated, via differential screening of a Petunia hybrida peta
l cDNA library, a cDNA clone that corresponds to the Rt locus which co
ntrols the conversion of anthocyanidin-3-glucosides to anthocyanidin-3
-rutinosides by the UDP rhamnose: anthocyanidin-3-glucoside rhamnosylt
ransferase (3RT). The cDNA encodes a 469 amino acid long polypeptide w
ith regions of similarity to the UDP glucose: flavonoid glucosyltransf
erases (3GT) from barley and maize. Some sequence similarity was also
observed with non-plant glycosyltransferases. Two aberrant transcripts
are present in most of the rt/rt petunia lines examined. Excision of
a transposon from an unstable Rt locus of one petunia line (Tr38) is a
ssociated with a change in transcript size back to wild-type. The Rt t
ranscript is most abundant in petals from flowers at an early stage of
development and levels decline as the flower matures. Transcripts are
also detected in the style and anthers but not in leaf, stem, root, p
etiole, ovary or sepals. Incubation of leaves in glucose under high li
ght conditions induces the expression of the Rt gene as well as other
flavonoid pathway genes. In situ hybridization revealed that the Rt tr
anscript predominantly accumulates in the epidermal cells of the petal
, the site of anthocyanin accumulation.