The potato P locus codes for flavonoid 3',5'-hydroxylase.

Area of Science:

• Plant Genetics
• Biochemistry
• Molecular Biology

Background:

• The potato P locus controls the production of blue/purple anthocyanin pigments.
• Previous RFLP mapping in tomato suggested a link between the P locus and the flavonoid 3',5'-hydroxylase (f3'5'h) gene.

Purpose of the Study:

• To identify and characterize the potato gene homologous to the anthocyanin biosynthetic enzyme f3'5'h.
• To confirm the association between this gene and the P locus controlling purple pigmentation in potatoes.

Main Methods:

• Screening a potato cDNA library using a Petunia f3'5'h gene probe.
• Sequencing of positive cDNA clones and amino acid sequence comparison.
• Cosegregation analysis with purple tuber color and expression studies in relation to the I locus.
• Agrobacterium-mediated transformation of a potato f3'5'h cDNA into red-skinned potatoes.

Main Results:

• A potato gene sharing 85% amino acid identity with Petunia f3'5'h was identified.
• This potato f3'5'h gene cosegregated with purple tuber color and its expression was dependent on the I locus.
• Transgenic potato lines expressing the f3'5'h gene exhibited purple coloration in tubers and stems.

Conclusions:

• The identified potato f3'5'h gene is likely the functional equivalent of the P locus.
• This gene plays a crucial role in anthocyanin biosynthesis, determining purple pigmentation in potato.
• Genetic engineering of f3'5'h can confer purple color to red-skinned potato cultivars.