Genomic Characterization Of Putative Allergen Genes In Peach And Their Expression In Different Tissues

The identified peach allergens belong to mainly four protein families: pathogenesis related 10 proteins, thaumatin-like proteins, lipid transfer proteins and profilins. In peach(Prunus persica), these allergen gene families are designated as Pru p 1 to 4 and for almond(Prunus dulcis) Pru du 1 to 4. This study was to characterize putative peach allergen genes for their genomic sequences and linkage map positions, and to compare them with previously characterized homologous genes in apple (Malus domestica). In the present study, spatial transcript expression of the four putative allergen-coding gene families in peach fruit, anther and leaf was monitored by real-time PCR to gain insight into their expression profile and key members involved in peach allergy. The main results were summarized as following:1. A total of 18 putative peach/almond allergen genes have been mapped on five linkage groups. Their positions confirm the high macro-synteny between peach/almond and apple. Eight Pru p/du 1 genes were identified, four of which were new. All the Pru p/du 1 genes were mapped in a single bin on the top of G1. Five Pru p/du 2 genes were mapped on four different linkage groups, two very similar Pru p/du 2.01 genes (A and B) were on G3, Pru p/du 2.02 on G7, Pru p/du 2.03 on G8 and Pru p/du 2.04 on Gl. There were differences in the intron and exon structure in these Pru p/du 2 genes and in their amino acid composition. Three Pru p/du 3 genes (3.01-3.03) containing an intron and a mini exon of 10 nt were mapped in a cluster on G6. Pru p/du 4.01 and 4.02 were located on Gl and G7, respectively. The Pru p/du 1 cluster on G1 aligned to the Mal d 1 clusters on LG16; Pru p/du 2.01 A and B on G3 to Mal d 2.01 A and B on LG9; the Pru p/du 3 cluster on G6 to Mal d 3.01 on LG12; Pru p/du 4.01 on G1 to Mal d 4.03 on LG 8; and Pru p/du 4.02 on G7 to Mal d 4.02 on LG2.2. Transcript abundance and expression patterns of the eighteen isoallergens were heterogeneous, depending on the specific isoallergen and tissues examined, especially between epicarp and mesocarp. Pru p 1.01, Pru p 1.06B, Pru p 3.01, Pru p 4.01 and Pru p 4.02 were predominant. Transcript levels in mesocarp was significant lower than in epicarp. Few isoallergens exhibited tissue specificity:Pru p 3.02 was only detected in leaf whereas Pru p 3.03 only in anther. Pru p 1.02 was abundant in leaf but absent in fruit tissues. A thorough analysis on the transcript expression of all peach putative isoallergens derived from genomic research showed differential spatial transcript profile in peach fruit, anther and leaf. Specific isoallergens was predominant in these tissues. These results can provide preliminary implications towards key genes involved in allergenicity difference and their diverse biological roles.