Scots pine expresses short-root-specific peroxidases during development

Nine short-root-specific proteins from Scots pine (Pinus sylvestris L.) det ected and isolated as individual spots by 2D-PACE were identified. The simi lar peptide mass maps obtained for all nine polypeptide spots together with lectin-blotting results suggest that they represent forms of the same modi fied protein. N-Terminal sequence analysis of two of the peptides showed hi gh similarity to peroxidases. RT-PCR with oligonucleotide primers correspon ding to determined peptide sequences and conserved regions in plant peroxid ases led to isolation of Psyp1 cDNA which is most abundantly expressed in s hort roots. Psyp1 is the first peroxidase cDNA to be isolated from the genus Pinus. It encodes a 363-amino-acid class-III peroxidase with a calculated molecular m ass of 35.7 kDa and theoretical pi of 4.74. The predicted PSYP1 amino-acid sequence is grouped with other class-III peroxidases in phylogenetic analys es, but it has a unique amino-acid sequence which may be associated with it s function in short roots or with its phylogenetic group. The presence of a signal sequence for extracellular transport indicates that PSYP1 belongs t o the group of secreted class-III peroxidases. The presence of 10 tyrosine residues and putative auxin-binding regions in PSYP1 suggests that the func tion of the enzyme is associated with cell-wall formation in short roots. T he downregulation of Psyp1 expression in symbiotic short roots hosting the ectomycorrhizal fungus Suillus bovinus is perhaps related to the change in cell-wall structure necessary for ectomycorrhizal development.