Expression profiling of flavonoid biosynthesis genes in association with accumulation of flavonoid compounds in rice under water deficit stress

Abstract

Aim: To investigate whether the phenolic and flavonoid contents have any direct relation with the water deficit stress tolerance in rice. If so, then, which genes in the flavonoid biosynthesis pathway are involved in the tolerance mechanism was explored by comparing a well-known water deficit tolerant cv. Nagina 22 (N22) as experiment material along with a sensitive cv. Pusa Sugandh 2 (PS2). Methodology: Water deficit stress was imposed on N22 (drought tolerant) and PS2 (drought sensitive) cultivars at the seedling stage by withholding water for 7days. Further, the expression level of flavonoid biosynthesis genes (OsCHS, OsCHI, OsF3H, OsF3’H, OsDFR, and OsANS) and the accumulation of total contents of phenolics and flavonoids in rice leaves of N22 and PS2 under water deficit stress were also investigated. Results: Quantitative RT-PCR analysis revealed enhanced expression of six major genes of the flavonoid biosynthesis pathway, namely OsCHS, OsCHI, OsF3H, OsF3’H, OsDFR, and OsANS in the drought tolerant cv. N22 compared to the drought sensitive cv. PS2 under water deficit stress. Accumulation of total phenolics and flavonoids compounds increased during water deficit stress in both the genotypes, but, it was significantly higher in N22 as compared to PS2. Interpretation: Our findings conclude that enhanced drought tolerance is positively correlated with an enhanced transcription of flavonoid biosynthesis genes and higher flavonoid content, suggesting that there could be differences in the genetic control of flavonoid metabolism in rice for drought stress response that, the enhanced expression and accumulation of flavonoids is promising strategy for rice improvement.