Peach Associated With The Development Of Mads Box Genes

The knowledge of the genetic control of flowering time and floral organ development in peach may have a significant importance for fruit improvement in Prunus species. More than ten QTLs and major loci associated with blooming time and flower development were identified in Prunus species; however, the molecular factors that control these traits are largely unknown. In contrast, many genes known to control flowering time and floral organ formation have been identified and characterized in model plants, mainly in Arabidopsis thaliana, and a complex network has been established. In this network, floral organ identity genes, MADS box genes, play crucial roles. Assuming that a similar mechanism controls flower development in the model herbaceous and in Prunus species, we should be able to identify candidate key genes homologous with those of model plants and then associate them with the above mentioned traits.In this paper we report the isolation of eight MADS box genes with complete coding region. Through analyses of their gene sequences and phylogeny it was revealed that they belonged to the distinct clades of the floral identity gene families.PrpMADS2, PrpMADS5 and PrpMADS7, which belong to distinct SEP gene clades, appear as single copy genes in the peach genome and were found to preferentially express in flower organs and fruits. Arabidopsis transformants expressing 35S::PrpMADS2 were indistinguishable from wild type plants. Overexpression of PrpMADS5 led to earlier flowering. Through chimeric repressor silencing technology, PrpMADS5 was found to function in floral organ development. Expression of PrpMADS7 in Arabidopsis caused a dramatic attenuation of both juvenile and adult growth phases and, in severely affected plants, it led to flower formation immediately after the embryonic phase.PrpMADS4, PrpMADS8, PrpMADS9, PrpMADS10 and PrpMADS11 are the putative orthologues of AG, SHP, STK, PI and TM6, respectively. Overexpressing PrpMADS4 in Arabidopsis demonstrate it can function like AGAMOUS.Moreover, based on the sequence variations three SSR markers were developed for PrpMADS2, PrpMADS4 and PrpMADS5. PrpMADS2 and PrpMADS4 were assigned to the linkage group 5 and PrpMADS5 to the group 1. We could not find co-locolization between our MADS box genes and the loci reported that control flower development in peach.