Transcriptome analysis of giant pear fruit with fruit-specific DNA reduplication on a mutant branch

Because bud mutation occurs in a specific part of a plant, the genomic backgrounds of mutant and wild-type branches are identical except for mutations. Therefore, bud mutants are ideal for identifying key genes governing important crop traits. We studied Giant La France (GLaF), a bud mutant setting large fruit, which appeared spontaneously in the European pear (Pyrus communis L.) 'La France'. In GLaF, increased cell size and DNA reduplication occurred specifically in fruit flesh. With the goal of identifying genes expressed differentially between GLaF and 'La France', microarray analysis was performed with RNA extracted from the receptacle (fruit flesh) 1 week before the full bloom stage. The receptacle was isolated by laser microdissection. Genes encoding proteins localized in the nucleus and cytoskeleton were up-regulated in GLaF. Among these genes, several were homologous to genes previously described to be associated with DNA reduplication. These might be related to the molecular mechanism of GLaF fruit size mutation.