To avoid the long time required for conventional sexual crossing, transgenic tobacco (Nicotiana tabacum L.) plants harboring phbA gene (encoding 3_ketothiolase) were used as the target plant for the second transformation mediated by Agrobacterium tumefaciens (Smith et Townsend) Conn LBA4404 containing pZCB which was constructed by linking phbB (encoding acetoacetyl_CoA reductase), phbC (encoding PHB synthase) and ctp sequence to pBIB_HYG under the control of CaMV 35S promoter. The hygromycin resistant transformants were morphologically normal and stable integration of phbB and phbC was confirmed by PCR and PCR_Southern. Moreover, RT_PCR_DNA hybridization analysis showed that 6.67% of the transformed tobacco plants could express both phbB and phbC at transcriptional level.
cDNA encoding caffeoyl CoA O-methyltransferase (CCoAOMT) from Chinese white poplar ( Populus tomentosa Carr.) was cloned by RT-PCR and sequenced. Northern analysis displayed that the CCoAOMT was expressed specifically in the developing secondary xylem and its expression was coincident with lignification. The antisense CCoAOMT cDNA was transformed into P. tremula x P. alba mediated by Agrobacterium tumefaciens ( Smith et Townsend) Conn. Transgenic plants were identified with PCR, PCR-Southern and Southern analysis. Lignin content in 5- to 6-month-old transgenic plants was measured. One of the transgenic lines had significant reduction of 17.9% in Klason lignin content as compared with that of untransformed poplar. The results demonstrate that antisense repression of CCoAOMT is an efficient way to reduce lignin content for improving pulping property in engineered trees.
