Light and developmental regulation of the Anp-controlled anthocyanin phenotype of bean pods.

In the presence of the dominant allele of the Anp gene, bean pods present a purple-mottled phenotype. The purple pigmentation is variable from cell to cell in the pod epidermal layer and develops as a random mosaic. Three anthocyanidins, delphinidin, petunidin and malvidin, are involved in this purple pigmentation. Anthocyanins accumulated in vacuoles; anthocyanoplasts and cristal bodies were also observed occasionally. A developmental switch is a prerequisite for anthocyanin accumulation in the pods. This does not occur before day 4 after pollination and is controlled by light in competent pods. mRNAs for PAL, CHS, CHI, DFR and UFGT are induced in the pods, indicating that the general anthocyanin biosynthetic pathway is well conserved at both the biochemical and molecular levels in this species. mRNA steady-state level studies of PAL and CHS suggest that the light regulation occurs at the transcriptional level.