A strawberry fruit-specific and ripening-related gene codes for a HyPRP protein involved in polyphenol anchoring.

A strawberry (Fragaria x ananassa cv. Chandler) fruit cDNA (Fahyprp-cDNA) and its corresponding gene (Fahyprp) showing sequence homology to higher plant hyprp genes have been isolated. The cDNA contains an open reading frame encoding a 16 kDa protein with 156 amino acids. The peptide has an amino-terminal signal sequence, a repetitive proline-rich sequence, and a cysteine-rich carboxy-terminal region homologous to other HyPRP proteins. Northern blot and QRT-PCR analysis have shown that the strawberry transcript is specifically expressed in fruit, not being detected in other plant tissues. “In situ” hybridization and immunolocalization studies have indicated that the Fahyprpgene is strongly expressed in achene sclerenchyma cells, in the vascular and receptacle cells of immature green fruit and in the vascular cells of mature red fruits. The achenes removal from unripe green fruits induced the expression of this Fahyprp gene. This induction was reverted by treatment of deachened fruit with the auxin NAA, supporting the idea that Fahyprp gene expression is regulated by auxins. Furthermore, the HyPRP protein has been localized in parenchymatic cells of immature fruits associated to structures containing condensed tannins. The results are discussed supporting a putative role of this protein in the anchoring of polymeric polyphenols in the strawberry fruit during growth and ripening.