Abstract
Cultured asparagus (Asparagus officinalis) cells induced to regenerate into whole plants through somatic embryogenesis secreted a 38-kDa protein into cell walls. The full length cDNA sequence of this protein (AoPOX1) determined by RT-PCR showed similarity with plant peroxidases (POX). AoPOX1 transcripts were particularly abundant during early somatic embryogenesis. To evaluate the in vivo function of AoPOX1 protein, purified recombinant AoPOX1 protein was reacted with a series of phenolic substrates. The AoPOX1 protein was effective in the metabolism of feruloyl (o-methoxyphenol)-substituted substrates, including coniferyl alcohol. The reaction product of coniferyl alcohol was fractionated and subjected to GC-MS analysis and 1H-NMR analysis, indicating that the oxidation product of coniferyl alcohol in the presence of AoPOX1 was dehydrodiconiferyl alcohol (DDCA). The concentration of DDCA in the cultured medium of the somatic embryos was in the range of 10-8 M. Functions of the AoPOX1 protein in the cell differentiation are discussed.
