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A giant-fruited mutant of European pear (Pyrus communis L.), Giant La France (GLaF), that arose from a bud sport of normal 'La France', exhibited receptacle-specific DNA reduplication resulting in an approx. 1.6-fold increase in fruit size compared with normal 'La France' fruit. To identify the genes responsible for this receptacle-specific DNA reduplication, we focussed on the regulatory genes WEE1 and CCS52A, which have been reported to increase the ploidy level of tomato fruit flesh. Full-length cDNAs of WEE1 and CCS'52/1, referred to as PcWEEl and PcCCS52A, were cloned from P. communis L., 'La France'. We determined the genomic sequences of these two genes, clarified their exon-intron structures, and compared cDNA sequences between 'La France' and GLaF. The predicted amino acid sequences were similar to other species and retained their conserved domains. No differences were found between the PcWEEl and PcCCS52A cDNA sequences of'La France' and GLaF. However, analysis revealed that the levels of expression of PcWEEl and PcCCS52A were higher in the receptacles of GLaF than in those of 'La France' 1 week before the full-bloom stage. Our results suggest that PcWEEl and PcCCS52A may play important roles in the occurrence and persistence of DNA reduplication in the receptacles, and hence fruit, of GLaF. [ABSTRACT FROM AUTHOR]

We studied Giant La France (GLaF), a sport that sets large fruit and that appeared spontaneously on a European pear (Pyrus communis L.) 'La France' tree. It is known that GLaF exhibits DNA reduplication, specifically in the receptacle, before full bloom. To identify the genes related to DNA reduplication in GLaF, we performed 454 pyrosequencing to obtain mRNA sequences from GLaF and 'La France' and to examine their levels of expression. In total, 1,166,675 sequences were obtained from the poly(A)-enriched complimentary DNA libraries of GLaF and 'La France' and assembled into 49,181 contigs. A further 78,431 sequences were obtained as singletons. Comparisons of the total RNA sequence abundance between GLaF and 'La France' revealed that the levels of expression of 26 genes changed significantly in GLaF. However, none of these genes had an obvious functional role that could explain the difference in fruit size between the GLaF sport and 'La France'. We also identified 61 core cell cycle genes by transcriptome analysis, but their involvement in the larger fruit size of GLaF remains to be elucidated. This study presents the first large-scale RNA sequence database for European pear using next-generation sequencing technology. The resuhs obtained can assist in various studies concerning pear physiology, including clarification of the molecular basis for the GLaF sport mutation. [ABSTRACT FROM AUTHOR]