Stress-inducible expression of chalcone isomerase2 gene improves accumulation of flavonoids and imparts enhanced abiotic stress tolerance to rice

Abstract Analysis of rice microarray data indicated that a gene encoding for chalcone isomerase2 (OsCHI2) showed upregulation in response to abiotic stress. Hence, we isolated OsCHI2 from a popular drought tolerant upland rice variety Nagina22 and developed transgenic plants of a drought stress sensitive rice cv. Pusa Sugandh 2 expressing OsCHI2 under the control of stress inducible promoter AtRd29A and further studied their response to different abiotic stresses. Stable chromosomal integration of transgene was confirmed in the transgenic plants through PCR, Southern hybridization and expression analysis. Physio-biochemical studies revealed that the Rd29A::OsCHI2 transgenic rice plants upheld higher relative water content, more photosynthetic pigments and proline with lower relative electrolyte leakage and less malondialdehyde content as compared to WT plants under abiotic stresses. Quantitative RT-PCR analysis demonstrated that the expression level of the transgene in the OsCHI2 transgenic lines was higher than WT plants under stress conditions. Stress-inducible expression of OsCHI2 also enhanced transcript abundance of structural genes of flavonoids biosynthesis pathway leading to higher production of flavonoids under abiotic stresses in the transgenic plants. In brief, our results demonstrated that OsCHI2 is not only capable of modulating flavonoid metabolism but also can impart enhanced adaptation to different abiotic stresses other than heat stress.