ORIGINAL PAPER Generation and characterization of transgenic poplar plants overexpressing a cotton laccase gene Ji Wang Æ Chenglong Wang Æ Mulan Zhu Æ Yang Yu Æ Yuebo Zhang Æ Zhiming Wei Received: 22 August 2007 / Accepted: 29 March 2008 / Published online: 11 April 2008 Ó Springer Science+Business Media B.V. 2008 Abstract Laccases are copper-containing glyco- proteins, which are widespread in higher plants as multigene families. To gain more insight in the function of laccases in plants, especially potential role in lignification, we produced transgenic poplar plants overexpressing a cotton laccase cDNA (GaLAC1) under the control of the cauliflower mosaic virus 35S promoter. As compared with untransformed control plants, transgenic plants exhibited a 2.1- to 13.2-fold increased laccase activity, whereas plant growth rate and morpholog- ical characters remained similar to control plants. A 2.1–19.6% increase in total lignin content of the stem was found in transgenic plants. Moreover, transgenic plants showed a dramatically accelerated oxidation rate of phenolics, without obvious change in total phenolic content. Our data suggested that GaLAC1 may participate in lignin synthesis and phenolic metabolism in plants. The present work provided a new genetic evidence for the involve- ment of plant laccases in lignification. Keywords Laccase Á Lignin Á Phenolic metabolism Á Populus Á Transgenic poplars Abbreviations ABTS 2,2-Azino- bis(3-ethylbenzothiazoline- 6-sulfonic acid) AS Acetosyringone BAP Benzylaminopurine CaMV 35S promoter Cauliflower mosaic virus 35S promoter IAA Indole-3 acetic acid PSK-a Phytosulfokine-a ZT Zeatin Introduction Laccases (p-diphenol:O 2 oxidoreductase, EC 1.10.3.2) is a class of copper-containing, cell wall-localized glycoproteins that can catalyze reduction of O 2 to water by oxidizing phenolic substrates. Laccases have been found to be widely distributed in various J. Wang Á C. Wang Á M. Zhu Á Y. Yu Á Z. Wei (&) Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China e-mail: zmwei@sippe.ac.cn J. Wang Á C. Wang Á M. Zhu Á Y. Yu Graduate School of the Chinese Academy of Sciences, Shanghai 200032, China Y. Zhang Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China 123 Plant Cell Tiss Organ Cult (2008) 93:303–310 DOI 10.1007/s11240-008-9377-x