Zhang Zhe, Chen Yunli, Yang Fang, Yang Kunjian, Li Wenqiao, Zhang Xiao, Liu Wanhong, Deng Hongping
Key Laboratory of Eco-Environment in the Three Gorges Reservoir Region, Ministry of Education, School of Life Sciences, Southwest University, Chongqing 400715, China.
School of Chemistry and Chemical Engineering, Chongqing University of Science and Technology, Chongqing 401331, China.
Plants (Basel). 2025 Aug 24;14(17):2636. doi: 10.3390/plants14172636.
Drought stress limits seedling growth, hindering morphological development and population establishment. , a critically endangered species endemic to the karst regions of southwest China, exhibits poor population structure and limited natural regeneration in the wild, with water deficit during the seedling stage identified as a major factor contributing to its endangered status. Elucidating the physiological and molecular mechanisms underlying drought tolerance in seedlings is essential for improving their drought adaptability and facilitating population recovery. In this study, 72 two-year-old seedlings were divided into two groups: drought (PEG) and ethephon (PEG + Ethephon), and subjected to drought-rehydration experiments. The results showed that exogenous application of 100 mg·L ethephon significantly improved stomatal conductance and photosynthetic pigment content in seedlings. Under drought stress, the PEG + Ethephon group exhibited rapid stomatal closure, maintaining water balance and higher photosynthetic pigment levels. After rehydration, the PEG + Ethephon group significantly outperformed the PEG group in terms of photosynthetic rate. Ethephon treatment reduced HO and MDA levels, enhanced antioxidant enzyme activity (SOD, CAT, POD, GR), and increased osmotic regulator activity (soluble sugars, soluble proteins, and proline), improving ROS-scavenging capacity and reducing oxidative damage. Ethephon application significantly enhanced ethylene accumulation in seedlings, while drought stress stimulated the concentrations of key ethylene biosynthetic enzymes (SAMS, ACS, and ACO), thereby further contributing to improved drought resistance. Transcriptomic data revealed that drought stress significantly upregulated key ethylene biosynthesis genes, with expression levels increasing with stress duration and rapidly decreasing after rehydration. WGCNA analysis identified eight key drought-resistance genes, providing valuable targets for future research. This study provides the first mechanistic insight into the physiological and molecular responses of seedlings to drought and rehydration, underscoring the central role of endogenous ethylene in drought tolerance. Ethephon treatment effectively enhanced ethylene accumulation and biosynthetic enzyme activity, thereby improving drought adaptability. These findings lay a theoretical foundation for subsequent molecular functional studies and the conservation biology of this endangered species.
干旱胁迫限制幼苗生长，阻碍形态发育和种群建立。 是中国西南喀斯特地区特有的极度濒危物种，其种群结构不佳，野外自然更新有限，幼苗期水分亏缺被认为是导致其濒危状态的主要因素。阐明 幼苗耐旱性的生理和分子机制对于提高其干旱适应性和促进种群恢复至关重要。在本研究中，将72株两岁大的幼苗分为两组：干旱组（PEG）和乙烯利组（PEG + 乙烯利），并进行干旱 - 复水实验。结果表明，外源施加100 mg·L乙烯利显著提高了 幼苗的气孔导度和光合色素含量。在干旱胁迫下，PEG + 乙烯利组气孔迅速关闭，维持水分平衡并保持较高的光合色素水平。复水后，PEG + 乙烯利组在光合速率方面显著优于PEG组。乙烯利处理降低了HO和MDA水平，增强了抗氧化酶活性（SOD、CAT、POD、GR），并提高了渗透调节物质活性（可溶性糖、可溶性蛋白和脯氨酸），提高了ROS清除能力并减少了氧化损伤。乙烯利处理显著增强了幼苗中乙烯的积累，而干旱胁迫刺激了关键乙烯生物合成酶（SAMS、ACS和ACO）的浓度，从而进一步有助于提高抗旱性。转录组数据显示，干旱胁迫显著上调了关键乙烯生物合成基因，其表达水平随胁迫持续时间增加而升高，复水后迅速下降。WGCNA分析确定了八个关键抗旱基因，为未来研究提供了有价值的靶点。本研究首次深入了解了 幼苗对干旱和复水的生理和分子反应，强调了内源乙烯在耐旱性中的核心作用。乙烯利处理有效增强了乙烯积累和生物合成酶活性，从而提高了干旱适应性。这些发现为后续分子功能研究和该濒危物种的保护生物学奠定了理论基础。
