Strand Deserah D, Livingston Aaron K, Satoh-Cruz Mio, Froehlich John E, Maurino Veronica G, Kramer David M
Plant Research Laboratory and Departments of Plant Biology and.
School of Molecular Biosciences and Institute for Biological Chemistry, Washington State University, Pullman, WA 99164; and.
Proc Natl Acad Sci U S A. 2015 Apr 28;112(17):5539-44. doi: 10.1073/pnas.1418223112. Epub 2015 Apr 13.
Cyclic electron flow (CEF) around photosystem I is thought to balance the ATP/NADPH energy budget of photosynthesis, requiring that its rate be finely regulated. The mechanisms of this regulation are not well understood. We observed that mutants that exhibited constitutively high rates of CEF also showed elevated production of H2O2. We thus tested the hypothesis that CEF can be activated by H2O2 in vivo. CEF was strongly increased by H2O2 both by infiltration or in situ production by chloroplast-localized glycolate oxidase, implying that H2O2 can activate CEF either directly by redox modulation of key enzymes, or indirectly by affecting other photosynthetic processes. CEF appeared with a half time of about 20 min after exposure to H2O2, suggesting activation of previously expressed CEF-related machinery. H2O2-dependent CEF was not sensitive to antimycin A or loss of PGR5, indicating that increased CEF probably does not involve the PGR5-PGRL1 associated pathway. In contrast, the rise in CEF was not observed in a mutant deficient in the chloroplast NADPH:PQ reductase (NDH), supporting the involvement of this complex in CEF activated by H2O2. We propose that H2O2 is a missing link between environmental stress, metabolism, and redox regulation of CEF in higher plants.
围绕光系统I的循环电子流（CEF）被认为是为了平衡光合作用中ATP/NADPH的能量收支，这就要求其速率受到精确调控。然而，这种调控的机制尚未完全明确。我们观察到，那些表现出持续高CEF速率的突变体也显示出过氧化氢（H2O2）产量的增加。因此，我们测试了H2O2在体内能否激活CEF这一假设。通过渗透或叶绿体定位的乙醇酸氧化酶原位产生H2O2，均可使CEF显著增加，这意味着H2O2可能通过对关键酶进行氧化还原调节直接激活CEF，或者通过影响其他光合过程间接激活CEF。暴露于H2O2后约20分钟，CEF出现，这表明之前表达的与CEF相关的机制被激活。依赖H2O2的CEF对抗霉素A不敏感，也不受PGR5缺失的影响，这表明CEF的增加可能不涉及与PGR5-PGRL1相关的途径。相反，在叶绿体NADPH:PQ还原酶（NDH）缺陷的突变体中未观察到CEF的增加，这支持了该复合体参与H2O2激活的CEF过程。我们提出，H2O2是高等植物环境胁迫、代谢和CEF氧化还原调节之间缺失的一环。
