Abstract
Opisthopappus taihangensis (Ling) Shih, as a relative of chrysanthemum, mainly survives on the cracks of steep slopes and cliffs. Due to the harsh environment in which O. taihangensis lives, it has evolved strong adaptive traits to drought stress. The root system first perceives soil water deficiency, triggering a multi-pronged response mechanism to maintain water potential; however, the drought tolerance mechanism of O. taihangensis roots remains unclear. Therefore, roots were selected as materials to explore the physiological and molecular responsive mechanisms. We found that the roots had a stronger water retention capacity than the leaves. This result was attributed to ABA accumulation, which promoted an increased accumulation of proline and trehalose to maintain cell osmotic pressure, activated SOD and POD to scavenge ROS to protect root cell membrane structure and induced suberin depositions to minimize water backflow to dry soil. Transcriptome sequencing analyses further confirmed that O. taihangensis strongly activated genes involved in the ABA signalling pathway, osmolyte metabolism, antioxidant enzyme activity and biosynthesis of suberin monomer. Overall, these results not only will provide new insights into the drought response mechanisms of O. taihangensis but also will be helpful for future drought breeding programmes of chrysanthemum.
Highlights
Chrysanthemum (Chrysanthemum × morifolium Ramat.) is one of the most valuable ornamental flowers in the world[12]
The root system of plants is responsive for water absorption and firstly perceive the decrease in soil water potential, triggering the sophisticated water stress responsive mechanisms to hold water potential[37]
At the beginning of this study, we found that the RWC of the root zone decreased by 7.81% at the first stage and remained relatively constant from 3 h to 24 h after PEG treatment, while the RWC of the leaves decreased by 36.46%
Summary
Chrysanthemum (Chrysanthemum × morifolium Ramat.) is one of the most valuable ornamental flowers in the world[12]. Recent studies have indicated that the CmWRKY10, DgNAC1, and ClCBF1 transcription factors could improve the level of drought tolerance in C. morifolium[18,19,20]. Some candidate genes of chrysanthemum and O. taihangensis have been explored, the regulatory mechanisms of the drought stress response in O. taihangensis roots are not well understood. O. taihangensis mainly survives on the cracks of steep slopes and cliffs at an altitude of approximately 1000 m in the Taihang Mountains (Supplementary Fig. S1) This habitat determines that its root system has strong water absorption and water retention abilities. Our study aims to effectively screen physiological changes and identify candidate genes in the response of O. taihangensis roots to drought stress
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