Unlocking the Synergy: ABA Seed Priming Enhances Drought Tolerance in Seedlings of Sweet Sorghum Through ABA‐IAA Crosstalk

Abscisic acid (ABA) seed priming impacts plant growth and stress resistance, yet its precise physiological and molecular mechanisms remain elusive. This study explored the role of ABA-priming in enhancing drought acclimation in sweet sorghum (Sorghum bicolor Moench) using physiological assessments and comparative transcriptomics. Under drought stress, ABA-primed seedlings exhibited increased plant height, larger leaves, and higher leaf water content compared to non-primed plants. While drought negatively affected photosynthesis through the regulation of photosystem I and II, ABA-priming improved photosynthesis and WUE by involving in differential expression of photosystem II genes. ABA-priming promoted the accumulation of cuticular wax and cutin, effectively reducing leaf water loss. Drought triggered endogenous ABA production via ABA inactivation genes (UGT, BGLU), while ABA-priming activated auxin (IAA) biosynthesis via YUCCA, enhancing auxin-mediated responses and gibberellic acid (GA) signalling. The synergistic action of ABA and IAA culminated in enhanced drought tolerance. Additionally, ABA-priming and drought stress regulated NAC transcription factors, with SbNAC21-1 emerging as a pivotal transcriptional activator intricately linked to auxin signalling. Overexpression of SbNAC21-1 in Arabidopsis effectively enhanced drought tolerance. These findings offer valuable insights into the intricate mechanisms underpinning the beneficial effects of ABA-priming, ultimately enhancing plant adaptability to environmental stressors.