Expression and function of cell wall-bound cationic peroxidase in asparagus somatic embryogenesis

Area of Science:

• Plant molecular biology
• Biochemistry
• Plant biotechnology

Background:

• Asparagus officinalis L. cv Y6 cells undergoing somatic embryogenesis secrete a 38-kD protein into cell walls.
• The gene encoding this protein is Asparagus officinalis peroxidase 1 (AoPOX1).
• AoPOX1 exhibits sequence similarity to plant peroxidases and is highly expressed during early somatic embryogenesis.

Purpose of the Study:

• To elucidate the in vivo function of the AoPOX1 protein.
• To investigate the enzymatic activity of AoPOX1 on phenolic substrates.
• To identify the metabolic products of AoPOX1 activity during somatic embryogenesis.

Main Methods:

• Determining the full-length cDNA sequence of AoPOX1 using reverse transcriptase-polymerase chain reaction.
• Purifying recombinant AoPOX1 protein.
• Reacting purified AoPOX1 with phenolic substrates.
• Analyzing reaction products using gas chromatography-mass spectrometry and (1)H-nuclear magnetic resonance.

Main Results:

• AoPOX1 effectively metabolizes feruloyl-substituted phenolic substrates, notably coniferyl alcohol.
• The primary oxidation product of coniferyl alcohol by AoPOX1 was identified as dehydrodiconiferyl alcohol.
• Dehydrodiconiferyl alcohol was detected at concentrations of 10(-8) M in the culture medium of somatic embryos.

Conclusions:

• AoPOX1 plays a significant role in the metabolism of phenolic compounds during asparagus somatic embryogenesis.
• The production of dehydrodiconiferyl alcohol by AoPOX1 is implicated in cell differentiation processes.
• AoPOX1 is a key peroxidase involved in plant cell development and potentially in the formation of secondary metabolites.