In the present study,a vector of pAN580-PpCAD was constructed based on the cDNA sequence of PpCAD gene from elephant grass (Pennisetum purpureum cv.Huanan),and transformed to elephant grass protoplasts by PEG-mediated method,attempting to figure out the subcellular localization of PpCAD protein.At the same time,the sense vector pBA002-PpCAD was constucted and overexpressed in tobacco by Agrobacterium-mediated method,aiming to study the relationship between PpCAD and plant lignin biosynthesis.The results showed that:(1)PpCAD was located in the cytoplasm of elephant grass protoplasts.(2)27 transgenic tobacco plants were obtained after transformed with overexpression vector pBA002-PpCAD,of which,25 plants were identified positive by PCR.(3)The expression levels of 6 transgenic plants were different after analyzed by semiquantitative RT-PCR.The Southern blot indicated the expression level was related to the insert copy number of target gene.(4)There was no obvious phenotype difference between PpCAD overexpressed plants and wild type,but the lignin contents were increased in varying degrees among 6 transgenic plants except OEC6.Compared with wild type,the maxium amplification rate of lignin content was 56.50%.This study demonstated that PpCAD was a cytoplasmic protein.Overexpression of PpCAD in tobacco would lead to a increase of lignin content,which indicated that PpCAD was involve in plant lignin biosynthesis and it could be available for regulation of elephant grass lignin biosynthesis.