Regulatory mechanisms of Nitraria tangutorum in response to drought stress and functional verification of NtPP2C51-like

Nitraria tangutorum is a pioneer shrub species for windbreak and sand fixation in desert regions. Drought stress caused by continuous global warming poses a significant environmental challenge to the growth and development of N. tangutorum . This study employed the N. tangutorum 2-17-16 from the Zhangye provenance as the experimental material to analyze the physiological and biochemical changes and transcriptome data of N. tangutorum seedlings under PEG-simulated drought stress, systematically elucidating the regulatory mechanisms underlying responses to drought stress in N. tangutorum at physiological and molecular levels. Furthermore, the function of the core regulatory gene NtPP2C51-like in drought resistance responses of N. tangutorum was investigated via heterologous overexpression in Nicotiana benthamiana . The results indicated that N. tangutorum responded to PEG-simulated drought stress by specifically increasing the content of osmoprotectants and activity of antioxidant enzymes. Under PEG-simulated drought stress, differentially expressed genes were significantly enriched in pathways such as Plant hormone signal transduction and MAPK signaling pathway-plant. Genes such as IAA , GID1 , ETR , EBF1/2 , and PP2C play significant roles in the response of N. tangutorum to drought stress. Under drought stress, N. benthamiana plants overexpressing NtPP2C51-like exhibited faster water loss, higher MDA content, lower contents of osmoprotectants, and lower antioxidant enzyme activities than wild-type plants. At 7 d of drought treatment, MDA content in the overexpression lines was 1.31–1.39-fold higher, whereas soluble sugar content was only 57–61% of that in wild-type plants, indicating that NtPP2C51-like overexpression increases drought sensitivity in the heterologous N. benthamiana system and suggesting a potential negative role of NtPP2C51-like in the drought response of N. tangutorum . These results provide a theoretical basis for understanding the physiological and molecular mechanisms underlying drought adaptation in N. tangutorum and provide candidate genes for further drought-tolerance studies and genetic improvement of this ecologically important desert plant overall.