Marker-free, Tissue-specific Expression of Cry1Ab in Rice

Rice is an important staple crop to about half of the world's population. However, rice production can be severely decreased by insect infestation. Yongbin Qi from the Zhejiang Academy of Agricultural Sciences in China, together with other scientists, conducted a study to improve the insect resistance of rice and at the same time reduce Bt toxin levels released in the environment. The team conjugated the Cry1Ab gene into the rice rbcS promoter to express Bt toxin only in particular tissues of transgenic rice plants.

Eight marker-free, T₂ lines were selected from the T₀ co-transformants. Using RT-PCR, the team found high levels of Cry1Ab expression in the leaves but not in the seeds of the transgenic plants. ELISA results confirmed the presence of Cry1Ab protein (1.66 µg g^-1 to 3.31 µg g^-1) in the leaves but negligible in the seeds. In addition, bioassays also showed that the mortality rate of silkworm larvae that fed on diets with GM rice flour and pollen was lower than the positive control and that their average weight was higher than the positive control. This implies that the Bt protein was not expressed in the seed and pollen.

Subscribers of Pest Management Science journal may view the article at http://onlinelibrary.wiley.com/doi/10.1002/ps.3379/abstract.