基于生理和转录组解析褪黑素提高杜鹃花热耐受的机制

doi:10.1016/j.jia.2023.07.005

摘要/Abstract

摘要：

杜鹃花是杜鹃花属的总称，是具有很高的观赏和经济价值的著名木本植物。热胁迫是影响杜鹃花生长的主要环境因子。褪黑素近年来被报道可以缓解非生物胁迫对植物的影响。然而，褪黑素在杜鹃花中的作用尚不清楚。本研究探讨了褪黑素对热胁迫下杜鹃花的影响及其潜在机制。叶绿素荧光结果表明，喷施200 µmol L^-1褪黑素对杜鹃花抵抗热胁迫效果最佳。为了阐明褪黑素如何限制高温的不利影响，本研究分别在25、35和40°C处理下分析了杜鹃花叶片中褪黑素含量、光合参数、Rubisco酶活性和ATP含量。结果表明，与对照相比，外源喷施褪黑素提高了杜鹃花叶片中褪黑素含量、热应激下的电子传递速率、光系统II和I活性、Rubisco酶活性和ATP含量。转录组分析结果表明，许多热胁迫下的差异表达基因富集在光合作用途径，这些基因中的大部分均在热处理后下调表达，且在无褪黑素处理的植株中下调幅度大于外源喷施褪黑素处理的植株。本研究鉴定出RhPGR5A、RhATPB、RhLHCB3和RhRbsA作为关键基因。综合以上结果，我们推测褪黑素通过调控包括RhRbsA在内的特定基因的表达，促进光合电子传递，提高卡尔文循环酶活性，增加ATP的产生，由此提高了热应激下的光合效率和CO₂同化能力。因此，施用外源褪黑素可提高杜鹃花对热胁迫的耐受性。

Abstract:

Rhododendron is a well-known genus consisting of commercially valuable ornamental woody plant species. Heat stress is a major environmental factor that affects rhododendron growth. Melatonin was recently reported to alleviate the effects of abiotic stress on plants. However, the role of melatonin in rhododendron plants is unknown. In this study, the effect of melatonin on rhododendron plants exposed to heat stress and the potential underlying mechanism were investigated. Analyses of morphological characteristics and chlorophyll a fluorescence indicated 200 µmol L^–1 was the optimal melatonin concentration for protecting rhododendron plants from heat stress. To elucidate how melatonin limits the adverse effects of high temperatures, melatonin contents, photosynthetic indices, Rubisco activity, and adenosine triphosphate (ATP) contents were analyzed at 25, 35, and 40°C, respectively. Compared with the control, exogenous application of melatonin improved the melatonin contents, electron transport rate, photosystem II and I activities, Rubisco activity, and ATP contents under heat stress. The transcriptome analysis revealed many of the heat-induced differentially expressed genes were associated with the photosynthetic pathway; the expression of most of these genes was down-regulated by heat stress more in the melatonin-free plants than in the melatonin-treated plants. We identified RhPGR5A, RhATPB, RhLHCB3, and RhRbsA as key genes. Thus, we speculate that melatonin promotes photosynthetic electron transport, improves Calvin cycle enzyme activities, and increases ATP production. These changes lead to increased photosynthetic efficiency and CO₂ assimilation under heat stress conditions via the regulated expression of specific genes, including RhRbsA. Therefore, the application of exogenous melatonin may increase the tolerance of rhododendron to heat stress.

Key words: ornamental woody , high temperature , stress , melatonin , photosynthesis

XU Yan-xia, ZHANG Jing, WAN Zi-yun, HUANG Shan-xia, DI Hao-chen, HE Ying, JIN Song-heng. 基于生理和转录组解析褪黑素提高杜鹃花热耐受的机制[J]. Journal of Integrative Agriculture, 2023, 22(8): 2397-2411.

XU Yan-xia, ZHANG Jing, WAN Zi-yun, HUANG Shan-xia, DI Hao-chen, HE Ying, JIN Song-heng. Physiological and transcriptome analyses provide new insights into the mechanism mediating the enhanced tolerance of melatonin-treated rhododendron plants to heat stress[J]. Journal of Integrative Agriculture, 2023, 22(8): 2397-2411.

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