Cloning and functional identification of a Chilo suppressalis-inducible promoter of rice gene, OsHPL2.

BACKGROUND: Promoter plays a key role in driving insect-resistant genes in breeding of transgenic plants. In the current transgenic breeding process of rice resistance to striped stem borer (Chilo suppressalis Walker, SSB), the constitutive promoter is used to drive insect-resistant gene. To reduce the burden of plant growth caused by constitutive promoters, isolation and identification of insect-inducible promoters are particularly significant. However, there are few promoters specifically induced by insect feeding. RESULTS: We found that the rice hydroperoxide lyase gene (OsHPL2) (LOC_Os02g12680) was up regulated after feeding by SSB. Subsequently, we cloned the promoter of OsHPL2 and analyzed its expression pattern using the beta-glucuronidase (GUS) reporter gene. Histochemical assays and quantitative analyses of GUS activity confirmed that PHPL2 :GUS was activated by SSB and did not respond to brown planthopper (Nilaparvata lugens Stal, BPH) infested, mechanical wounding, or phytohormone treatments. A series of 5' truncated assays were conducted and three positive regulatory regions (-1452 to -1213, -903 to -624, -376 to -176) which were induced by infestation of SSB were identified. The P2R123-min 35S and P2TR2-min 35S promoters linked with cry1C of transgenic plants showed the highest expressions of Cry1C protein and SSB larval mortalities. CONCLUSION: We identified a SSB-inducible promoter and three positive regions inside, and the transgenic rice plants with OsHPL2 promoter and its positive regions driving cry1C, exhibited expected larvicidal effect on SSB. Our study is the first report of a SSB-inducible promoter that could be used as a potential resource for breeding insect-resistant transgenic crops. This article is protected by copyright. All rights reserved.