| Lignin is an abundant secondary product after cellulose in plants with important biofuntions. But in the paper pulping process, removing lignin by chemical methods not only lead to very seriously environmental pollution ,but also increase the cost of paper making. The purpose of our study is to regulate the lignin biosynthesis of Chinese white poplar(Populus tomentosa) on molecular level by antisense RNA technology to breed the resource tree species more suitable for paper making in China. Here are the main results of the study: (1) Antisense CCoAOMT cDNA,antisense COMT cDNA and both of them were respectively transformed into tobacco mediated By Agrobacterium tumficense. The results of PCR and PCR-Southern confirmed that the transgenes had integrated into the tobacco genome. Northern dot analysis showed that the antisense cDNAs had expressed at the transcriptional level. After growing about 3 months in the green house, the transgenic plants were conducted for Klason lignin and histochemical anaylesis. The results showed that down-regulating CCoAOMT resulted in the reduction of the lignin content of tobacco efficiently. Simultaneous repression of CCoAOMT and COMT had combinative effects on lignin content. Down-regulating COMT led to the reduction of S-lignin content of the transgenic plants, which demonstrated that COMT was a critical enzyme in the S-lignin biosynthesis. Moreover, the transgenic lines were foundamentally consistent with the control plants during the development and growth. Our study further proved the function of the two OMTs in the lignin biosynthesis and provided theoretical basis for regulating the lignin biosynthesis of Chinese white poplar by the genetic engineering; (2).The system of tissue culture and transformation of the triploid Chinese white poplar was established for the first time,which lay a foundation for regulationof the lignin biosynthesis by gene engineering and biotechnology in Chinese white poplar.
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