Expression and regulation of a pear polygalacturonase inhibitor protein gene (PpPGIP1) during fruit development, under salicylic acid treatment, and in diseased fruit

Abstract

To elucidate the roles of genes during fruit development, a fruit-predominant cDNA (designated PpPGIP1) encoding a polygalacturonase inhibitor protein (PGIP) was isolated from a pear (Pyrus pyrifolia Nakai. cv. Whangkeumbae) fruit cDNA library. The PpPGIP1 gene shares high sequence homology at the nucleotide level in the coding region and at the amino acid level with other plant PGIP genes. Subsequently, the corresponding PpPGIP1 gene was isolated from pear genomic DNA. Real-time quantitative PCR analyses revealed that PpPGIP1 transcripts were functionally accumulated during the developing fruit of pear. The PpPGIP1 expression signals were detected at relatively low level in early stage of pear fruit development (30–140 days after full bloom). With the fruit ripening, softening and senescence, the expression of PpPGIP1 gene increased to a relative high level in 150–180 days after full bloom fruit. In addition, PpPGIP1 gene was dramatically up-regulated in 180 days after full bloom diseased fruit and by 0.2 mM salicylic acid (SA) treatment for 12 h in 150 days after full bloom fruit. These results suggested that PpPGIP1 might play an important role in response to disease resistance and SA during fruit development of pear.