Two pear auxin-repressed protein genes, PpARP1 and PpARP2, are predominantly expressed in fruit and involved in response to salicylic acid signaling

Abstract

Two genes encoding putative auxin-repressed proteins, designated PpARP1 and PpARP2, were isolated from pear (Pyrus pyrifolia). The deduced PpARP1 and PpARP2 proteins contain the typical auxin_repressed Dormancy/auxin associated protein domains. Phylogenetic analyses clearly demonstrated that PpARP1 has high homology with pear ARPs except PpARP2 which belongs to another clade. Using PCR amplification technique, the genomic clones corresponding to PpARP1 and PpARP2 were isolated and shown to contain two introns with typical GT/AG boundaries defining the splice junctions. PpARP1 and PpARP2 genes were predominantly expressed in fruit. PpARP1 transcripts were also detected in shoots, petals, and anthers, but a relatively low expression signal was detected in young leaves. PpARP2 transcripts were also detected in other tissues. In particular, expression of PpARP1 and PpARP2 was developmentally regulated in fruit. Further study demonstrated that PpARP1 and PpARP2 expression in pear fruit was remarkably inhibited by salicylic acid and induced by IAA. These data suggested that PpARP1 and PpARP2 might be involved in the response to salicylic acid signaling during fruit development of pear. The study of the pear PpARP genes also demonstrated a link between salicylic acid and auxin signaling.