Exogenous strigolactones alleviate drought stress in wheat (Triticum aestivum L.) by promoting cell wall biogenesis to optimize root architecture.

Exogenous strigolactones (SLs, GR24) are widely used to alleviate drought stress in wheat. The physiological and biochemical mechanisms via which SLs help overcome drought stress in wheat shoots have been reported; however, the mechanisms in wheat roots are unclear. The present study explored the effects of the exogenous application of SLs on wheat roots' growth and molecular responses under drought stress using physiological analysis and RNA-seq. RNA-seq of roots showed that SLs mainly upregulated signal transduction genes (SIS8, CBL3, GLR2.8, LRK10L-2.4, CRK29, and CRK8) and transcription factors genes (ABR1, BHLH61, and MYB93). Besides, SLs upregulated a few downstream target genes, including antioxidant genes (PER2, GSTF1, and GSTU6), cell wall biogenesis genes (SUS4, ADF3, UGT13248, UGT85A24, UGT709G2, BGLU31, and LAC5), an aquaporin-encoding gene (TIP4-3), and dehydrin-encoding genes (DHN2, DHN3, and DHN4). As a result, SLs reduced oxidative damage, optimized root architecture, improved leaf-water relation, and alleviated drought damage. Thus, the present study provides novel insights into GR24-mediated drought stress management and a scientific basis for proposing GR24 application.