PpAG1, a homolog ofAGAMOUS, expressed in developing peach flowers and fruit

Abstract

MADS-box transcription factors are known to play a central role in floral organ identity and floral meristem determinacy in many gymnosperms and angiosperms. Studies of this nature are limited in fruit tree species despite the economic importance of this group. A peach ( Prunus persica (L.) Batsch) gene, PpAG1, was isolated and shown to be homologous to the Arabidopsis thaliana (L.) Heynh. MADS-box gene AGAMOUS (AG). It is a single gene in peach and codes for a type II or MIKC-type MADS-box protein. The features of the deduced protein sequence indicate that it is similar to other AG homologs from woody plant species. The spatial and developmental patterns of expression parallel those of AG and homologs from other angiosperms with similar floral structures but with some minor differences. In the floral meristem, where AG is responsible for conversion of the vegetative meristem into the floral meristem, the differentiation of the whorls that generate the carpels and stamens coincides with the tissue-specific expression of PpAG1. It continues to be expressed in the ovules, developing fruit and seeds that subsequently develop from the carpels. Constitutive overexpression of PpAG1 in Arabidopsis, using the 35S promoter, caused the homeotic conversion of sepals to carpelloid tissues and altered petal development. This is consistent with C-function genes according to the ABC model of flower development. The data support the conclusion that PpAG1 is the peach homolog of Arabidopsis AG.