Enhances the resistance of rice to lepidopteran pests by fusing the Cry1Ca and Cry2Aa genes with self-cleavage peptide sequence.

Background: Accumulation of two or more Bacillus thuringiensis (Bt) proteins in plant not only improves the resistance to pests and broadens the resistance spectrum of crops, but also delays the development of pest resistance.

Results: The self-cleavage peptide sequence was used to link two codon-optimized genes, so as to achieve simultaneous accumulation of two low homologous insecticidal proteins in one plant. The rice transformants accumulating Cry1Ca and Cry2Aa proteins were fed to local lepidopteran pests and the larva mortality in 5 days were 100%. The sum of Cry1Ca and Cry2Aa proteins in leaves of transformants E1C&2A-1 and E2A&1C-18 were 10.60 and 9.55 μg g^-1 fresh weight (FW), respectively, and the larva mortality of fall armyworm fed on their leaves for 5 days reached 100%. For the control transformants that expressed one Bt protein, the content of Cry1Ca in leaves of transformant E1CM031 was 14.94 μg g^-1 FW, and that of Cry2Aa in leaves of transformant B2A4008S was 11.90 μg g^-1 FW, but the larva mortality of fall armyworm fed on leaves of E1CM031 and B2A4008S for 5 days were 77.78% and 52.78%, respectively. Although the total Bt contents in transformants expressing one Bt protein were higher than that of transformants expressing two Bt proteins, the lethality of transformants expressing one Bt protein were obviously lower than that of transformants expressing two Bt proteins.

Conclusion: The lethal effect of accumulating both Cry1Ca and Cry2Aa proteins in rice was stronger than that of amassing Cry1Ca or Cry2Aa protein only, which meant there was synergistic effect between Cry1Ca and Cry2Aa proteins. © 2024 Society of Chemical Industry.