Novel small molecules targeting bZIP23 TF improve stomatal conductance and photosynthesis under mild drought stress by regulating ABA

• Published in: The FEBS journal Vol. 289; no. 19; pp. 6058 - 6077
• Main Authors: PA, Vanitha, Vijayaraghavareddy, Preethi, Uttarkar, Akshay, Dawane, Akashata, D, Sujitha, V, Ashwin, KC, Babitha, Niranjan, Vidya, MS, Sheshshayee, CV, Anuradha, Makarla, Udayakumar, Vemanna, Ramu S.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.10.2022
• Subjects: ABA; Abscisic acid; Antagonists; Biosynthesis; Conductance; Crop production; Drought; Fertility; Gene regulation; Genomics; Germination; Photosynthesis; Plants (botany); Productivity; Rice; Seeds; Serotonin; small molecules; Soybeans; Stomata; Stomatal conductance; Stress; transcription factor; Water relations; ABA; transcription factor; rice; drought; photosynthesis; small molecules
• ISSN: 1742-464X; 1742-4658
• DOI: 10.1111/febs.16461

Drought‐induced abscisic acid (ABA) accumulation plays a key role in plant water relations by regulating stomatal movements. Although ABA helps in the survival of the plants, reduced carbon gain affects plant productivity. To improve crop productivity under mild drought stress conditions, it is necessary to manipulate ABA responses. Other research groups have used forward chemical genomics for the identification of ABA agonists and antagonists aiming to manipulate ABA biosynthesis and signalling. In the present study, we identified indolyl‐ethyl amine and serotonin small molecules using a reverse chemical genomics approach, with these acting as potent inhibitors of ABA biosynthesis through transient regulation of bZIP23 transcription factor activity. In rice, wheat and soybean, each of the small molecules enhanced the germination of seeds, even in the presence of ABA. These molecules nullified the effect of ABA on intact and detached leaves, resulting in higher photosynthesis. Furthermore, these small molecules effectively reduced the transcription levels of bZIP23 targeting NCED4, PP2C49 and CO3 genes. Rice plants treated with the small molecules were found to have improved stomatal conductance, spikelet fertility and yield compared to untreated plants under mild drought stress conditions. Our results suggest that indolyl‐ethyl amine and serotonin small molecules could be utilized to improve yield under mild drought conditions. The small‐molecule indolyl‐ethyl amine (IEA) and serotonin inhibit OsbZIP23 transcription factor activity. Inhibition of OsbIZP23 results in downregulation of NCED4, an abscisic acid (ABA) biosynthesis gene, and PP2C49, involved in ABA signalling. The small molecules reduce the effect of ABA‐induced seed germination in rice, soybean and wheat. Exogenous application of small molecules on rice plants exposed to mild drought increases the stomatal conductance and photosynthesis to maintain yields.