Effects of exogenous GR24 on the growth and gene expression of maize seedlings under drought stress

The growth and production of maize (Zea mays L.) are severely impaired by drought stress. Strigolactones (SLs), a novel class of phytohormones, play key roles in regulating plant development and adaptation to drought stress. However, little is known regarding how GR24 (a synthetic SL analog) modulates the growth and gene expression of maize seedlings to drought stress (DS). In this study, we conducted physiological analysis and transcriptome sequencing to investigate the mechanisms by which GR24 alleviates DS-induced effects on maize seedlings. Our results revealed that compared to seedlings subjected to DS alone, GR24 application significantly increased leaf fresh weight, leaf dry weight, root fresh weight, root dry weight, and leaf relative water content. Furthermore, chlorophyll a, b, and total chlorophyll content increased. Conversely, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and proline (Pro) content decreased. Following 10 days of rewatering, GR24-treated seedlings exhibited 100 % survival; leaf and root fresh weight increased by 223 % and 203 %, respectively, and leaf relative water content increased by 53 %. Meanwhile, MDA and proline content decreased by 87 % and 96 %, respectively. Transcriptome analysis indicated that exogenous GR24 enhanced maize drought tolerance by modulating plant hormone signal transduction and MAPK signaling pathway. Thus, exogenous GR24 effectively improves the drought tolerance and post-stress recovery capacity in maize seedlings.