Polyethylene Glycol Priming Improves Drought Resistance in Sweet Sorghum ( Sorghum bicolor ) via Hormone‐Mediated Regulation of Cuticular Wax Biosynthesis

ABSTRACT Seed priming is a widely used pre‐sowing treatment to enhance plant resistance to drought stress. However, the effects of seed priming with polyethylene glycol on plant cuticle, which plays a crucial role in reducing water loss, remain unclear. In this study, we primed sweet sorghum ( Sorghum bicolor (L.) Moench) seeds with PEG and subjected the seedlings to drought stress. PEG priming increased the accumulation of cuticular wax and cutin under drought conditions, resulting in reduced leaf water loss and improved leaf relative water content compared to non‐primed seedlings. Transcriptome and hormone analyses revealed that PEG priming influenced the accumulation of ACC, JA‐Ile, JA, ABA and SA under drought stress. Exogenous applications of ABA, JA and ABA/JA led to 6.1%, 19.7% and 23.1% increases in total wax coverage, respectively, on seedlings under non‐stress conditions. We also identified MYB30, a transcription factor from sorghum, and transgenically overexpressed it in Arabidopsis. The MYB30‐overexpression lines showed significantly increased wax accumulation and enhanced drought resistance compared to wild‐type (WT) plants. These findings suggest that PEG priming modulates hormone levels, which regulate transcription factors such as MYB30, ultimately promoting the expression of genes involved in wax and cutin biosynthesis and improving drought tolerance.