Effect of RNA Interference Triggered by Small Fragment of EuCAD Gene on Lignin Synthesis in Tobacco

【Objective】The study aimed to explore the key sequence of cinnamoyl alcohol dehydrogenase（CAD）gene of Eucalyptus urophylla and use them to regulate lignin synthesis.【Method】Sequence analysis of EuCAD gene was carried out by bioinformatics method. According to the distribution of conservative domain of coding protein, a 44 bp key sequence was obtained to construct RNA interference vector and transformed to tobacco. Transgenic plants were obtained and phenotypes such as gene expression and lignin content were detected.【Result】Twenty-eight transgenic lines were obtained, which grew normally as same as the wild type. Three transgenic lines were randomly selected for detection. The results showed that the expression level of CAD gene was significantly lower than that of wild type. The largest decline was observed in line R1 which decreased to 12.51% of the wild type. It was found that the stem diameter of line R1 was the same as that of the wild type, but the xylem thickness was significantly lower than that of the wild type, which decreased by 11.75% at the 4th node and 10.06% at the 6th node. The lignin content of the stem in line R1 decreased by 15.26% compared with that of the wild type. The results showed that the RNAi fragment significantly inhibited the expression of CAD gene in tobacco and affected the lignin synthesis of tobacco.【Conclusion】The small fragment of EuCAD gene screened by sequence analysis can significantly affect lignin synthesis in tobacco by triggering RNA interference, which provides a technical reference for the study on the regulation of lignin synthesis in E. urophylla.