Abstract:

It has long been postulated that the transfer of C₄ traits to C₃ plants could improve the photosynthetic performance of C₃ plant species. Several attempts have been made to transfer C₄ photosynthetic traits, with the emphasis on PEPC, to rice plants using genetic engineering techniques. The photosynthetic rates of transgenic rice plants over-expressed PEPC were comparable to those of the untransformed control plants. Recently, maize PEPC gene was first introduced into wheat and the same results were found. These results enlightened us to introduce PEPC into wheat to increase photosynthesis and yield. In this study, wheat calli derived from immature embryos of three cultivars of spring wheat (Yangmai 158, Bobwhite, and Yangmai 12) were cultured for 10 to 12 days and transformed with three strains of Agrobacterium tumefaciens (LBA4404, EHA105, and C58c1) harboring expression vector pUbi-Ecppc which carrying Gus, Hpt, Ecppc genes. Both Gus gene and Hpt gene are promoted by CaMV35S promoter, and Ecppc gene were promoted by maize Ubiquitin promoter. Factors that influence Agrobacterium-mediated wheat transformation, including concentration of antibiotics during selection, concentration of bacterium suspension, temperature and time of co-culture, receptor genotype and bacterium strains, were investigated. With the established wheat genetic transformation system, Ecppc from Echinochloa crusgalli was transferred into wheat firstly and hygomycin resistant plantlets were obtained, with a transformation efficiency of up to 3.03% in Yangmai 158. Fourteen PCR positive transgenic wheat plants from 816 co-cultured calli were obtained and the integration and transcription of transgene was confirmed by Southern blot and RT-PCR analysis. Physiological studies showed that the transformants displayed higher photosynthesis and PEPC activity.

Key words: Wheat, Phosphoenolpyruvate carboxylase (PEPC), Agrobacterium mediated transformation, Transgenic plant