Li Dejun, Xia Zhihui, Wang Xuncheng, Yang Hong, Li Yao
State Key Laboratory of Tropical Crop Breeding, Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture and Rural Affairs, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China.
Sanya Research Institute, Chinese Academy of Tropical Agricultural Sciences, Sanya 572025, China.
Plants (Basel). 2025 Jul 21;14(14):2243. doi: 10.3390/plants14142243.
Melatonin (MT) can enhance plant stress tolerance by activating the internal defense system, but its application in rubber trees has been barely reported up to now. In this study, we found that the relative electrical conductivity (REC), HO, and malondialdehyde (MDA) contents were significantly higher in the leaves of rubber tree seedlings under drought stress compared to the control (water treatment), whereas chlorophyll contents were obviously lower in the leaves under drought stress compared to the control. MT partly relieves the aforementioned drought-induced adverse effects by dramatically reducing chlorophyll degradation, HO accumulation, MDA content, and REC. Comparative transcriptomes among the PEG (P), MT (M), and PEG + MT (PM) treatments against the control showed that 213, 896, and 944 genes were differently expressed in rubber tree seedlings treated with M, P, and PM in contrast to the control. Among the 64 differently expressed genes (DEGs) being common among the three comparisons, the expression profiles of 25 were opposite in MH compared with PH. Intriguingly, all the KEGG pathways of the DEGs mentioned above belonged to metabolism including energy metabolism, carbohydrate metabolism, amino acid metabolism, and the metabolism of cofactors and vitamins. Exogenous application of MT mainly regulated the genes associated with photosynthesis and the anti-oxidative defense system, thereby enhancing the antioxidant protection of rubber tree seedlings under drought stress. These results suggest that exogenous melatonin application can effectively enhance drought tolerance by heightening ROS scavenging to decrease HO accumulation in rubber tree seedlings. Our results elucidate the molecular mechanisms of MT's roles in drought stress, which help to employ exogenous MT to boost drought tolerance in the rubber tree.
褪黑素（MT）可通过激活植物内部防御系统来增强其抗逆性，但迄今为止，其在橡胶树中的应用鲜有报道。在本研究中，我们发现，与对照（水处理）相比，干旱胁迫下橡胶树幼苗叶片的相对电导率（REC）、过氧化氢（HO）和丙二醛（MDA）含量显著更高，而干旱胁迫下叶片中的叶绿素含量明显低于对照。MT通过显著减少叶绿素降解、HO积累、MDA含量和REC，部分缓解了上述干旱诱导的不利影响。对聚乙二醇（P）、MT（M）和聚乙二醇+MT（PM）处理组与对照组进行比较转录组分析，结果显示，与对照组相比，M、P和PM处理的橡胶树幼苗分别有213、896和944个基因差异表达。在三个比较组中共有的64个差异表达基因（DEG）中，有25个基因在MH组中的表达模式与PH组相反。有趣的是，上述DEG的所有KEGG通路均属于代谢，包括能量代谢、碳水化合物代谢、氨基酸代谢以及辅因子和维生素代谢。外源施用MT主要调控与光合作用和抗氧化防御系统相关的基因，从而增强干旱胁迫下橡胶树幼苗的抗氧化保护能力。这些结果表明，外源施用褪黑素可通过增强活性氧清除能力以减少橡胶树幼苗中HO的积累，从而有效提高其耐旱性。我们的研究结果阐明了MT在干旱胁迫中发挥作用的分子机制，有助于利用外源MT提高橡胶树的耐旱性。
