Differential expression of two lipid transfer protein genes in reproductive organs of peach ( Prunus persica L. Batsch)

Abstract

Two cDNA clones (named Pp-LTP1 and Pp-LTP2) corresponding to different lipid transfer protein (LTP) genes have been isolated from peach ( Prunus persica L. Batsch) epicarp and ovary, respectively. Sequence analysis revealed that the two fragments share 54% identity at nucleotide level and show common features of plant LTP genes, such as conserved cysteine residues and lipid-binding motifs. Phylogenetic analysis grouped Pp-LTP1 and Pp-LTP2 in two distinct clusters, the former with most of LTP genes sequenced in the Rosaceae family, the latter only with one almond LTP. Genomic Southern data indicated that a small LTP gene family is present in peach. Pp-LTP1 and Pp-LTP2 have been used as gene-specific probes to describe expression in flowers and fruits throughout development. In petals, sepals and stamen only Pp-LTP1 was expressed whereas transcripts of Pp-LTP2 strongly accumulated in non-pollinated and pollinated ovary with a decreasing trend in the period of four weeks after pollination. In fruits, a dramatic accumulation of Pp-LTP1 mRNA was detected in epicarp at all stages of fruit development and, with the exception of the early growth stage, no Pp-LTP1 transcripts have been detected in mesocarp. When Pp-LTP2 was used as a probe in the same fruit tissues, a faint hybridisation signal was observed only in epicarp of fruitlets collected at an early growth stage. Infection with Monilia induced only a slight increase of Pp-LTP1 transcript in epicarp of pre-climacteric and climacteric fruits. These results support the hypothesis of multiple roles played by LTPs and, considering that LTPs have been recognised as the major allergen of peach, indicate that Pp-LTP1 could be related to the allergenicity of peach.