銅是植物生長發育所需的微量營養元素之一，參與多個生物生理過程，包括光合作用、呼吸、超氧化物清除、細胞壁代謝、木質化和乙烯感知。然而，當植物處於高濃度銅離子環境中，會對細胞造成許多有害影響，包括影響細胞壁穩定性、引發有害的氧化壓力 (ROS) 和對蛋白質、DNA 與其他生物分子造成損傷。在這種重金屬逆境下，細胞壁成為植物的第一道防線，起著至關重要的保護作用，因此 THE1 (THESEUS1) 被認為在細胞壁完整性和感知細胞壁損害中扮演重要角色，本研究發現，在 50 μM CuCl₂ 處理下，the1-1 突變株的生長受到顯著抑制且細胞死亡率高於野生型，胼胝質沉積顯著減少。此外，過氧化酵素 (POD) 活性在銅逆境下顯著增加，尤其是在突變株中，這表明植物在銅逆境下啟動了強烈的抗氧化防禦反應以應對氧化壓力；在基因表現方面，經過RT-qPCR實驗確認發現， 在銅逆境處理後MPK3基因表現量在the1-1突變株中相較於野生型被誘發的更高。在後續轉錄體分析以及RT-qPCR確認基因表現量後發現MAPK 訊息傳遞之 MEKK1、MKK2/MKK4被顯著上調，而防禦性相關基因在銅逆境下的表現也顯著上升，特別是與細胞壁生物合成、調控和防禦反應相關的基因在突變株中擁有更高的轉錄量。因此本研究揭示了 THE1 在銅逆境下對阿拉伯芥細胞壁完整性和防禦反應的影響，並且對於植物在銅逆境壓力下的生理生化反應具有重要影響。本研究不僅有助於理解植物在銅逆境下的反應，還可能為農作物在重金屬污染環境中的生長和生存能力提供新的觀點。

Copper is one of the essential micronutrients required for plant growth and development, participating in several physiological processes, including photosynthesis, respiration, superoxide scavenging, cell wall metabolism, lignification, and ethylene perception. However, when plants are exposed to high concentrations of copper ions, numerous harmful effects occur, including affecting cell wall integrity, generation of toxic free radicals leading to detrimental oxidative stress, which causing damage to proteins, DNA, and other biomolecules. Under heavy metal stress, the cell wall becomes the first line of defense for plants and plays a vital protective role. THE1 (THESEUS1) is thought to play an important role in maintaining cell wall integrity and sensing cell wall damage. This study found that under 50 μM CuCl₂ treatment, the growth of the1-1 mutant was significantly inhibited, compared with the wild type, cell death rate was higher and callose deposition was significantly reduced. Furthermore, peroxidase (POD) activity significantly increased under copper stress, especially in the mutant, indicating that plants activated a strong antioxidant defense response under copper stress to cope with oxidative stress. Meanwhile, RT-qPCR experiments confirmed that after copper stress treatment, the expression level of the MPK3 gene was induced higher in the the1-1 mutants compared to the wild type. Transcriptome analysis and RT-qPCR validation revealed that the MAPK signaling components MEKK1, MKK2/MKK4 were significantly upregulated. The expression of defense related genes also increased significantly under copper stress, particularly those involved in cell wall biosynthesis, regulation, and defense responses, which had higher transcription levels in the mutants.Therefore, this study reveals the impact of THE1 on cell wall integrity and defense responses in Arabidopsis thaliana under copper stress, its important role in plant physiological and biochemical responses under copper stress. This research not only helps to understand basic plant biology, but also provides a new perspective on the growth and survival ability of crops in heavy metal-contaminated environments.

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