Isolation and characterization of a novel peroxidase gene ZPO-C whose expression and function are closely associated with lignification during tracheary element differentiation.
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 x His-tagged ZPO-C was produced in tobacco cultured cells and purified. The ZPO-C:6 x 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.
Sato
Yasushi
Y
Department of Biology, Faculty of Science, Ehime University, Matsuyama, 790-8577 Japan. ysato@sci.ehime-u.ac.jp
Demura
Taku
T
Yamawaki
Ken
K
Inoue
Yukina
Y
Sato
Seiichi
S
Sugiyama
Munetaka
M
Fukuda
Hiroo
H
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D019659:Asteraceae / Q000166:cytology / Q000201:enzymology / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D002118:Calcium / Q000032:analysis; D002454:Cell Differentiation / Q000235:genetics; D002478:Cells, Cultured; D018076:DNA, Complementary; D018744:DNA, Plant / Q000032:analysis / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008031:Lignin / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D009195:Peroxidase / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D010802:Phylogeny; D018547:Plant Stems / Q000166:cytology / Q000201:enzymology* / Q000502:physiology; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D014026:Nicotiana / Q000166:cytology / Q000201:enzymology; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D018076:DNA, Complementary; D018744:DNA, Plant; D008164:Luminescent Proteins; D012333:RNA, Messenger; C054562:yellow fluorescent protein, Bacteria; D008031:Lignin; D009195:Peroxidase; D002118:Calcium