CLONING OF GENES ENCODING AUXIN-BINDING PROTEINS (ABP19 20) FROM PEACH - SIGNIFICANT PEPTIDE SEQUENCE SIMILARITY WITH GERMIN-LIKE PROTEINS/

An auxin-binding protein (ABP) was previously isolated from shoot apic es of peach trees to homogenity on standard SDS-PAGE. Analysis of low- bis SDS-PAGE and direct peptide sequencing of purified peach ABP demon strated that the ABP was composed of two types of polypeptides (design ated ABP19 and ABP20). Several cDNA and genomic clones which encode pe ach ABPs were obtained and analysed, We found that there are at least three classes of ABPs in the peach genome. Open reading frames of thes e ABPs were 627 bp, predicting a 209 amino acid polypeptide of 22 kDa. An N-terminal hydrophobic signal sequence of 18 amino acids and a put ative N-glycosylation. site at N-60-T-T/S were deduced. Homology searc h analysis revealed that ABP19 is highly homologous to proteins relate d to the germin family, The deduced amino acid sequence of ABP19 showe d very low overall sequence homology with ABP1, an ABP isolated from m aize coleoptile, but it contained a small region which shaped 40% homo logy with a putative auxin binding site in ABP1 (BoxA). In addition, t he sequence surrounding the region is highly conserved among peach ABP s and the germin family.