Plant Physiol, April 2003, Vol. 131, pp. 1765-1774
Expression and Function of Cell Wall-Bound Cationic Peroxidase in
Asparagus Somatic Embryogenesis
Hiroyuki
Takeda,
Toshihisa
Kotake,1
Naoki
Nakagawa,
Naoki
Sakurai,* and
Donald J.
Nevins
Faculty of Integrated Arts and Sciences, Hiroshima University,
Kagamiyama, Higashihiroshima, 739-8521, Japan (H.T., T.K., N.N.,
N.S.); and Department of Vegetable Crops, University of California,
Davis, California 95616 (D.J.N.)
Cultured asparagus (Asparagus officinalis L. cv Y6)
cells induced to regenerate into whole plants through somatic
embryogenesis secreted a 38-kD protein into cell walls. The full-length
cDNA sequence of this protein (Asparagus officinalis
peroxidase 1 [AoPOX1]) determined by reverse transcriptase-polymerase
chain reaction showed similarity with plant peroxidases.
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 gas
chromatography-mass spectrometry analysis and 1H-nuclear
magnetic resonance analysis, indicating that the oxidation product of
coniferyl alcohol in the presence of AoPOX1 was dehydrodiconiferyl alcohol. The concentration of dehydrodiconiferyl alcohol 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.
1
Present address: Faculty of Sciences, Saitama
University, Saitama, 338-0822, Japan.
*
Corresponding author; e-mail nsakura{at}hiroshima-u.ac.jp; fax
81-824-24-0758.
© 2003 American Society of Plant Biologists
