Objective To study the effects of the histone deacetylase inhibitor Trichostatin A (TSA) on the physiological characteristics of leaf morphology, photosynthetic indexes, proline, malondialdehyde and abscisic acid content, synthetic histone deacetylase, abscisic acid and flavonoid-related genes of sea buckthorn cuttings under the conditions of simulated drought and post-drought rehydration of 20% polyethylene glycol.

Methods The drought-related physiological indexes of sea buckthorn cuttings were measured, and the gene expression was detected by quantitative real-time PCR.

Result TSA-pretreated (1 μmol·L⁻¹) sea buckthorn was enhanced in drought tolerance under equal drought stress. Compared with the drought treatment, (1) the degree of leaf sagging and wilting reduced, the degree of fresh weight decline was smaller, and the degree of plant recovery after rehydration was greater. (2) The net photosynthetic rate, transpiration rate, stomatal conductivity, PSII maximum photochemical efficiency Fv/Fm value, PSII effective photochemical quantum yield Y(II) value and chlorophyll relative content (SPAD) value all significantly increased, and all were adjusted down after rehydration. (3) The content of proline and flavonoids increased significantly, the content of malondialdehyde and abscisic acid decreased significantly, and the trend was the same after rehydration. (4) The expression of histone deacetylase genes HrHDA6 and HrHDA19, abscisic acid synthesis-related genes ABF1 and NAC2 were significantly down-regulated, and the expression of flavonoid synthesis-related genes C4H2 and CHS4 were significantly upregulated, and the trend after rehydration was the same.

Conclusion TSA can improve the drought resistance of sea buckthorn by regulating the physiological and gene expression of sea buckthorn cuttings in response to drought stress, and this study lays an important foundation for in-depth analysis of the regulatory mechanism of histone acetylation affecting sea buckthorn drought resistance.