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.

Cloning and Characterization of Prunus serotina AGAMOUS, a Putative Flower Homeotic Gene

“…The high level of expression of PsAG detected in the carpel throughout flower development from early stage until flowers matured supported that PsAG was a C-function gene. This result was consistent with the expression pattern in PpAG (Martin et al 2006) and MdMADS4 (Sung et al 2000).…”

“…In situ hybridization and ectopic expression has been widely used to assess expression pattern of AG homologs. AG and its homologs are mainly expressed within the floral meristem, immature stamens, and immature carpel tissues (Brunner et al 2000;van der Linden et al 2002;Jager et al 2003;Martin et al 2006).…”

“…Among the floral MADS-box genes, AG functions sequentially in the establishment of the determinate floral meristem and later in the development of the stamens and carpels in the third and fourth whorls (Sieburth et al 1995;Martin et al 2006). There are several criteria for characterization of AG homologs.…”

“…Third, AG spatial expression was restricted to two inner (the third and fourth) whorls, where the stamen and carpel are normally located (Bowman et al 1991a, b). In Prunus, the AG gene has been cloned from peach (Prunus persica; Martin et al 2006) by screening cDNA libraries, and full cDNAs of AG of P. persica, Prunus mume, and Prunus dulcis have also been obtained (GenBank).…”

Isolation and Characterization of an AGAMOUS Homologue PmAG from the Japanese Apricot (Prunus mume Sieb. et Zucc.)

“…To date, AG homologues have been cloned and their function and structure have been studied in more than 20 species (Zahn et al 2006;Liu et al 2010). AG homologues have been isolated from fruit trees such as apple (van der Linden et al 2002), grapevine (Boss et al 2001), and peach (Wu et al 2004;Martin et al 2006). To our knowledge, there are no reports of AG homologues in the Japanese apricot.…”