Diverse roles for chloroplast stromal and thylakoid-bound ascorbate peroxidases in plant stress responses
Diverse roles for chloroplast stromal and thylakoid-bound ascorbate peroxidases in plant stress responses
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DOI：
10.1042/bj20080030
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发表时间：
2008-06-01
影响因子：
4.1
通讯作者：
Rintamaki, Eevi
中科院分区：
文献类型：
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作者：
Kangasjarvi, Saijaliisa;Lepisto, Anna;Rintamaki, Eevi
光合光反应包括在被照射的叶片中的过氧化氢（H2 O2）的重要来源。抗坏血酸过氧化物酶（APX）是将H2 O2还原为水的酶，在植物抗氧化系统中起重要作用。在本研究中，我们解决了拟南芥叶绿体APXs在胁迫耐受性和信号转导的意义。为此，T-DNA（转移DNA）插入突变体tapx，sapx和tapx sapx，缺乏tAPX（类囊体结合的APX），sAPX（基质APX）或两者，分别进行了表征。萌发过程中的光氧化胁迫导致漂白的叶绿体在sapx单突变体，特别是在tapx sapx双突变体植物，而野生型和tapx植物的绿化过程中只有部分受损。tapx sapx双突变体的成熟叶片也容易受到强光或甲基紫精处理诱导的短期光氧化胁迫。在强光或低温下驯化2周后，没有突变体表现出增强的胁迫症状。免疫印迹分析表明，高光应力驯化tapx sapx双突变体补偿的情况下，tAPX和sAPX的2-半胱氨酸过氧化物酶的水平增加。此外，tAPX和sAPX的情况下，诱导的tapx sapx双突变体植物的转录组学谱的变化已经在相当理想的生长条件下。我们得出结论，sAPX是特别重要的光保护在早期绿化过程中。在成熟叶片中，tAPX和sAPX在功能上是冗余的，并且在氧化应激突然发生时至关重要。此外，叶绿体APXs有助于叶绿体逆行信号转导途径后，在叶绿体中的积累H2 O2的轻微波动。
Photosynthetic light reactions comprise a significant source of hydrogen peroxide (H2O2) in illuminated leaves. APXs (ascorbate peroxidases) reduce H2O2 to water and play an important role in the antioxidant system of plants. In the present study we addressed the significance of chloroplast APXs in stress tolerance and signalling in Arabidopsis thaliana. To this end, T-DNA (transfer DNA) insertion mutants tapx, sapx and tapx sapx, lacking the tAPX (thylakoid-bound APX), sAPX (stromal APX) or both respectively, were characterized. Photo-oxidative stress during germination led to bleaching of chloroplasts in sapx single-mutant and particularly in the tapx sapx double-mutant plants, whereas the greening process of wild-type and tapx plants was only partially impaired. Mature leaves of tapx sapx double mutants were also susceptible to short-term photo-oxidative stress induced by high light or methyl viologen treatments. After a 2-week acclimation period under high light or under low temperature, none of the mutants exhibited enhanced stress symptoms. Immunoblot analysis revealed that high-light-stress-acclimated tapx sapx double mutants compensated for the absence of tAPX and sAPX by increasing the level of 2-cysteine peroxiredoxin. Furthermore, the absence of tAPX and sAPX induced alterations in the transcriptomic profile of tapx sapx double-mutant plants already under quite optimal growth conditions. We conclude that sAPX is particularly important for photoprotection during the early greening process. In mature leaves, tAPX and sAPX are functionally redundant, and crucial upon sudden onset of oxidative stress. Moreover, chloroplast APXs contribute to chloroplast retrograde signalling pathways upon slight fluctuations in the accumulation of H2O2 in chloroplasts.