DUF4057 Containing Express-Protein Negatively Regulates the Drought Responses in Rice

The current global climatic conditions project drought as a severe form of abiotic stress that directly impacts the agricultural productivity of economically important crops. In this study, we conducted a functional characterization of a drought-responsive express-protein (OsEP) that contains the DUF-4057 superfamily domain. In silico analysis revealed differential expression of the OsEP gene in two drought-responsive rice varieties with contrasting characteristics (Heena, drought-tolerant, and Kiran, drought-sensitive). According to phylogenetic analysis, OsEP showed a high amino acid identity with the protein of Panicum hallii and Zizania palustris. Following treatment with 20% PEG, quantitative real-time PCR demonstrated an increased abundance of OsEP gene transcripts. The OsEP gene exhibited the highest expression levels in the gynoecium and roots of the rice plant. Notably, rice lines over-expressing OsEP were found to be sensitive to PEG-induced drought stress, whereas knockdown lines exhibited improved root architecture and lignification of root cells, enabling them to withstand severe water deficit conditions. Furthermore, drought stress compromised the growth parameters and grain yield of OsEP over-expressing lines compared to knock-down lines. Increased activity of antioxidant enzymes such as CAT (catalase), APX (Ascorbate peroxidase), and SOD (Superoxide Dismutase) was observed in knock-down lines compared to both over-expressing lines and wild-type plants. Additionally, knock-down lines exhibited decreased levels of membrane stability marker (MDA) and electrolyte leakage, along with elevated proline content. Important regulatory genes such as OsHsfC1b, OsbZIP81, and OsNCED, positively impacted by osmotic/drought stress, exhibit variable expression in over-expressing and knock-down lines. These findings suggest that down-regulation of the OsEP gene modulates the genomic architecture of knock-down lines, allowing them to maintain cellular homeostasis by regulating enzymatic activity. Our results indicate that the OsEP gene is a negative regulator of drought response. Moreover, GA-JA (Gibberellic Acid-Jasmonic Acid) cross-talk is involved in the down-regulation of stress-related phenomena in over-expressing lines. Overall, this study sheds light on the crucial role of the DUF4057 superfamily gene in drought response and provides insights into its potential regulatory mechanism.