Isolation and Characterization of a Novel Peroxidase Gene ZPO-C Whose Expression and Function are Closely Associated with Lignification during Tracheary Element Differentiation.

Sato, Yasushi; Demura, Taku; Yamawaki, Ken; Inoue, Yukina; Sato, Seiichi; Sugiyama, Munetaka; Fukuda, Hiroo

In an attempt to elucidate the regulatory mechanism of vessel lignification, we isolated ZPO-C, a novel peroxidase gene of Zinnia elegans that is expressed specifically in differentiating tracheary elements (TEs). The ZPO-C transcript was shown to accumulate transiently at the time of secondary wall thickening of TEs in xylogenic culture of Zinnia cells. In situ hybridization indicated specific accumulation of the ZPO-C transcript in immature vessels in Zinnia seedlings. Immunohistochemical analysis using anti-ZPO-C antibody showed that the ZPO-C protein is abundant in TEs, especially at their secondary walls. For enzymatic characterization of ZPO-C, 6×His-tagged ZPO-C was produced in tobacco cultured cells and purified. The ZPO-C:6×His protein had a peroxidase activity preferring sinapyl alcohol as well as coniferyl alcohol as a substrate, with a narrow pH optimum around 5.25. The peroxidase activity required calcium ion and was elevated by increasing Ca2 concentration in the range of 0–10 mM. An Arabidopsis homolog of ZPO-C, At5g51890, was examined for expression patterns with transgenic plants carrying a yellow fluorescent protein (YFP) gene under the control of the At5g51890 promoter. The YFP fluorescence localization demonstrated vessel-specific expression of At5g51890 in the Arabidopsis roots. Taken collectively, our results strongly suggest that ZPO-C and its homologs play an important role in lignification of secondary cell walls in differentiating TEs.

PEROXIDASE; PLANT genetics; TRACHEARY cells; IN situ hybridization; ZINNIA; SEEDLINGS

Plant & Cell Physiology, 2006, Vol 47, Issue 4, p493

0032-0781

Academic Journal

10.1093/pcp/pcj016