ZFP37, C3H, NAC94, and bHLH148 transcription factors regulate cultivar-specific drought response by modulating r40C1 gene expression in rice

Lectins are gradually gaining importance in regulating abiotic stress response in plants. Among them, the R40 family plays pivotal role in regulating drought response. The expression of the Osr40C1 positively correlates with the degree of drought tolerance in indica rice cultivars. Although the mechanism of Osr40C1-mediated drought tolerance is well characterized, the gene's regulation under drought remains obscure. Here, we demonstrate that the Osr40C1 promoter is activated under drought to induce its transcription. A number of single nucleotide variations in the Osr40C1 promoter of the drought-tolerant IR36 and sensitive MTU1010 cultivar are detected. However, promoter swapping analysis reveals that these variations in the promoter sequence do not explain the cultivar-specific expression pattern of this gene. Next, we identified the transcription factors that interact with the Osr40C1 promoter. Among these transcription factors, OsZFP37, OsC3H, OsNAC94, and OsbHLH148 display significantly higher transcript abundance in IR36 compared with MTU1010. Furthermore, overexpression of each of these transcription factors confers drought tolerance, whereas their silencing leads to drought sensitivity. Interestingly, the Osr40C1 expression is significantly up-regulated in the transcription factor overexpression lines, while its expression is undetectable in the silencing lines. Together our study highlights how different transcription factors regulate the cultivar-specific expression pattern of Osr40C1 in rice.