Molecular and physiological mechanisms of strigolactones-mediated drought stress in crab apple (Malus hupehensis Rehd.) seedlings

Drought stress severely affects apple growth and yield. Therefore, it is urgent to identify an efficient and nonpolluting method to cope with drought stress. Strigolactones (SLs), a class of carotenoid-derived phytohor-mones, play an important role in regulating plant responses to abiotic stresses. However, the role of SLs in apple seedlings in response to drought stress remains unknown. In the present study, the ameliorative effects and underlying mechanism of exogenous GR24 (a synthetic SL analog) on apple seedlings under drought stress were studied. The results indicated that drought stress inhibited the growth of apple seedlings, whereas exogenous GR24 significantly ameliorated the damage caused by drought stress. Compared with drought treatment alone, GR24+drought treatment improved leaf chlorophyll contents, photosynthetic parameters and antioxidant ca-pacity and inhibited the production of reactive oxygen species (ROS) and malondialdehyde (MDA) in apple seedlings. RNA sequencing (RNA-seq) analysis showed that 6490 genes (2753 upregulated and 3737 down-regulated) were differentially expressed between the drought treatment (D) and the drought treatment with GR24 (DSL). Further analysis showed that these differentially expressed genes (DEGs) are mainly associated with stress response, antioxidant enzyme metabolism, calcium signaling and plant hormone signaling. In addition, several transcription factor families, such as WRKY, AP2/ERF, and NAC, are also activated by exogenous GR24. Taken together, our physiological and transcriptomic data revealed the mechanisms by which SLs alleviate drought stress, which may contribute to improving apple yield and quality under drought stress.

Automated summary

Exogenous GR24 can alleviate the damage caused by drought stress in apple seedlings by improving leaf chlorophyll contents, photosynthetic parameters, and antioxidant capacity while reducing reactive oxygen species and malondialdehyde production. RNA-seq analysis revealed that exogenous GR24 activates genes associated with stress response, antioxidant enzyme metabolism, calcium signaling, and plant hormone signaling. Therefore, SLs can alleviate drought stress in apples, contributing to improved yield and quality under drought conditions.