叶绿体脱氢抗坏血酸还原酶和谷胱甘肽共同决定光氧化胁迫条件下抗坏血酸积累的能力,The Plant Journal

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叶绿体脱氢抗坏血酸还原酶和谷胱甘肽共同决定光氧化胁迫条件下抗坏血酸积累的能力
The Plant Journal ( IF 6.2 ) Pub Date : 2023-01-24 , DOI: 10.1111/tpj.16117
Akane Hamada ₁ , Yasuhiro Tanaka _{1,

2} , Takahiro Ishikawa _{1,

2,

3} , Takanori Maruta _{1,

2,

3}

Affiliation

抗坏血酸是一种不可或缺的氧化还原缓冲液，对植物生长和胁迫适应至关重要。其氧化形式脱氢抗坏血酸 (DHA) 会快速降解，除非它通过谷胱甘肽 (GSH) 依赖性酶促或非酶促反应再循环回到抗坏血酸，而酶促反应由脱氢抗坏血酸还原酶 (DHAR) 催化。我们最近的研究利用拟南芥四重突变体 (Δ dhar pad2 )，它缺乏所有三种 DHAR (Δ dhar ) 并且缺乏 GSH ( pad2), 假设这些 GSH 依赖性反应以互补的方式运作, 使抗坏血酸在强光胁迫下大量积累。然而，由于拟南芥 DHAR 在胞质溶胶或叶绿体中发挥作用，目前尚不清楚哪种亚型在与 GSH 依赖性非酶促反应的合作中发挥更重要的作用。为了进一步理解植物中抗坏血酸循环系统的复杂网络，我们在另一个缺乏 GSH 的背景（cad2). 在由各种光强度或甲基紫精诱导的光氧化应激条件下，对这些突变体中抗坏血酸谱的综合比较明确表明，叶绿体 DHAR3（而非细胞溶质同种型）与 GSH 协同工作以积累抗坏血酸。我们的研究结果进一步表明，应激强度和循环能力之间的不平衡会显着影响抗坏血酸池的大小和对光氧化应激的耐受性。此外，发现缺乏 DHAR 和缺乏 GSH 不会阻碍抗坏血酸的生物合成，至少在生物合成酶的转录或活性方面是这样。这项研究提供了抗坏血酸回收稳健性的见解。

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Chloroplast dehydroascorbate reductase and glutathione cooperatively determine the capacity for ascorbate accumulation under photooxidative stress conditions

Ascorbate is an indispensable redox buffer essential for plant growth and stress acclimation. Its oxidized form, dehydroascorbate (DHA), undergoes rapid degradation unless it is recycled back into ascorbate by glutathione (GSH)-dependent enzymatic or non-enzymatic reactions, with the enzymatic reactions catalyzed by dehydroascorbate reductases (DHARs). Our recent study utilizing an Arabidopsis quadruple mutant (∆dhar pad2), which lacks all three DHARs (∆dhar) and is deficient in GSH (pad2), has posited that these GSH-dependent reactions operate in a complementary manner, enabling a high accumulation of ascorbate under high-light stress. However, as Arabidopsis DHAR functions in the cytosol or chloroplasts, it remained unclear which isoform played a more significant role in cooperation with GSH-dependent non-enzymatic reactions. To further comprehend the intricate network of ascorbate recycling systems in plants, we generated mutant lines lacking cytosolic DHAR1/2 or chloroplastic DHAR3, or both, in another GSH-deficient background (cad2). A comprehensive comparison of ascorbate profiles in these mutants under conditions of photooxidative stress induced by various light intensities or methyl viologen unequivocally demonstrated that chloroplastic DHAR3, but not cytosolic isoforms, works in concert with GSH to accumulate ascorbate. Our findings further illustrate that imbalances between stress intensity and recycling capacity significantly impact ascorbate pool size and tolerance to photooxidative stress. Additionally, it was found that the absence of DHARs and GSH deficiency do not impede ascorbate biosynthesis, at least in terms of transcription or activity of biosynthetic enzymes. This study provides insights into the robustness of ascorbate recycling.

更新日期：2023-01-24

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