Segregation and expression of transgenes in the progenies of <i>Bt</i> transgenic rice crossed to conventional rice varieties

Abstract

β-Glucuronidase (GUS) activity bioassay, western blotting and polymerase chain reaction (PCR) analysis demonstrated that the cry1Ab gene was closely inherited and expressed with reporter gene gus in the progenies of Bacillus thuringiensis (Bt) transgenic rice (Oryza sativa L.) crossed to conventional rice varieties. Therefore, it is feasible using GUS-assisted-selection to preliminarily identify the Bt gene and study the inheritance of transgenes in breeding program. Mendelian segregation was observed in BC1F1, BC1F2 and F2 populations derived from Bt rice crossed to japonica rice respectively which indicated that the cry1Ab gene was inherited as a single dominant locus. PCR, Southern blotting and Western dot blotting analysis confirmed that cry1Ab gene was transferred to the genome of conventional rice varieties and it was highly expressed in the different progenies of Bt rice crossed to conventional rice varieties. Among these lines, the highest Bt toxin protein content reached 2.88% of total soluble proteins, even though the amount of Bt toxin protein in leaves of some GUS positive plants was higher than that detected in the original Bt rice. Meanwhile, the variances in Bt toxin protein between crosses and its parents were significant at 0.05 or 0.01 levels, respectively. Therefore, foreign cry1Ab gene with native insect resistant trait can be easily transferred to other rice varieties with higher yield potential and good quality through classical breeding.

Keywords: Oryza sativa L., transgenes, inheritance, expression