Identification of a Peroxidase Enzyme Involved in Lignification

There are many isozymes of peroxidase in plants; therefore it is very important to identify the enzyme involved in lignification in order to inhibit lignin biosynthesis only.

Crude enzyme fractions were extracted from one year old hybrid aspen samples prepared every month and analyzed by isoelectric focusing. It was found that the acidic peroxidase isozyme clearly expresses in July, August and September, when lignin is synthesized vigorously, and that the lignification occurs in regenerated shoot and one year old trunk, but not in the callus, green callus and leaf. This isozyme band has a pI value of 3.8-4.2. Ultimately, we assumed that the acidic peroxidase enzyme is involved in lignification. Furthermore, in order to verify this assumption by histochemical localization analysis of this enzyme, we isolated the peroxidase isozyme and made a monoclonal antibody. We can find that immunogold-silver staining is detected in the xylem part near the cambial zone where lignin biosynthesis occurs in July. The lignification in July was also ascertained by ultraviolet microscopic observation.

Conclusively, this result indicates that this acidic peroxidase isozyme is involved in the lignification of hybrid poplar.

Fig. 26.1. Restriction enzyme maps of PAL genes from P. kitakamiensis. Bars indicate the probes used for Southern and Northern blot analyses. E: EcoRI, B: BamHI, P: Pstl, RV: EcoRV, Sl: Sail, Sc: Sad, X: Xhol.
Fig. 26.2. Restriction enzyme maps of OMT genes from P. kitakamiensis. Black and white boxes indicate exons and introns, respectively. Arrows indicate positions of primerse for PCR. E: EcoRI, B:BamHI, H: HindIII, Bg: BgUI, P: PstI, X: Xbal.
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