Abstract：Abstract The high-efficiency expression and stable inheritance of Bacillus thuringiensis gene (Bt) are crucial to transgenic rice breeding and commercial production. A transgenic line B2A68 (Oryza sativa) was obtained by introducing biplaphos resistance gene (Bar) and insecticidal crystal proteins gene (Cry2Aa) into the early season rice restorer line D68 via Agrobacterium mediated method. In this study, the temporal and spatial expression profile of Cry2Aa protein between homozygous and heterozygous genotype, different tissues and various developmental stages were studied by enzyme linked immunosorbent assay (ELISA), and the relationship between expression level, stage and tissue of insecticidal protein and insect resistance was revealed by referring bioassay results, in order to provide technical parameters for developing excellent lepidopteran resistant rice. The results showed that the expression level of Cry2Aa protein in homozygous plant leaf was significantly higher than that in heterozygous plant leaf (P＜0.01). At milk stage, the contents of Cry2Aa protein in each organ were: leaf ＞ glume and hulled grain ＞ stem and sheath (P＜0.05). At hard dough stage, the contents of Cry2Aa protein in each organ were: leaf ＞ hulled grain ＞ stem and glume (P＜0.05), but there were no significant differences in the contents of Cry2Aa protein between hulled grain and sheath, sheath and stem, and stem and glume, respectively. From seedling to ripening phase, the Cry2Aa protein content in leaf increased first, then decreased, and later increased again, fluctuating in a same pattern in T3 and T4 generation. The mortality of striped rice borer larvae was highly correlated with the Cry2Aa protein content in different organs at milk stage (r=0.837), and the mortality of rice leaf roller larvae was highly correlated with the Cry2Aa protein content in leaves at different stages (r=0.988). For the heterozygous plant leaf with low Cry2Aa protein content, the lethal time of the rice leaf roller feeding with heterozygous plant leaf was slightly longer than that of feeding with homozygous plant leaf, but shorter than 5 days. This study will contribute to controlling Lepidopteran pests in field and developing transgenic rice in the future.
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