The mitochondrial alternative oxidase pathway protects the photosynthetic apparatus against photodamage in Rumex K-1 leaves

BMC Plant Biology

Research Article

Jian-Guo Liu¹  Xiang-Long Meng²  Hui-Yuan Gao²  Qing-Wei Meng²  Zi-Shan Zhang²  Cheng Yang²  Li-Tao Zhang³ 

[1] Institute of Oceanology, Chinese Academy of Sciences, 266071, Qingdao, Shandong, China;State Key Laboratory of Crop Biology, Shandong Agricultural University, 271018, Tai'an, Shandong, China;State Key Laboratory of Crop Biology, Shandong Agricultural University, 271018, Tai'an, Shandong, China;Institute of Oceanology, Chinese Academy of Sciences, 266071, Qingdao, Shandong, China;

关键词: Electron Transport Rate;    Xanthophyll Cycle;    Sham Treatment;    Photosynthetic Electron Transport Chain;    Intense Light;   

DOI  :  10.1186/1471-2229-12-40

 received in 2011-07-31, accepted in 2012-03-20,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundIt is known that excess reducing equivalents in the form of NADPH in chloroplasts can be transported via shuttle machineries, such as the malate-oxaloacetate (OAA) shuttle, into the mitochondria, where they are efficiently oxidised by the mitochondrial alternative oxidase (AOX) respiratory pathway. Therefore, it has been speculated that the AOX pathway may protect plants from photoinhibition, but the mechanism by which this protection occurs remains to be elucidated.ResultsThe observation that the malate-OAA shuttle activity and the AOX pathway capacity increased markedly after intense light treatment in Rumex K-1 leaves indicates that excess NADPH was transported from the chloroplasts and oxidised by the AOX pathway. The inhibition of the AOX pathway by salicylhydroxamic acid (SHAM) caused the over-reduction of the photosystem I (PSI) acceptor side, as indicated by the increases in the extent of reduction of P700+. Furthermore, the photosynthetic linear electron flow was restricted, which was indicated by the decreases in the PSII electron transport rate (ETR) and the photosynthetic O2 evolution rate. The restriction of the photosynthetic linear electron flow, which generates the thylakoid ΔpH, inevitably decreased the de-epoxidation of the xanthophyll cycle (ΔPRI). Therefore, the induction of non-photochemical quenching (NPQ) was suppressed when the AOX pathway was inhibited. The effect of the inhibition of the AOX pathway on NPQ induction was less at 20 mM NaHCO3 than at 1 mM NaHCO3. The suppression of NPQ induction by the inhibition of the AOX pathway was also observed during the induction phase of photosynthesis. In addition, the inhibition of the AOX pathway increased the accumulation of hydrogen peroxide (H2O2), suggesting that the AOX pathway functions as an antioxidant mechanism.ConclusionsThe inhibition of the AOX pathway resulted in the rapid accumulation of NADPH in the chloroplasts, which caused the over-reduction of the PSI acceptor side. Furthermore, the restriction of the photosynthetic linear electron flow due to the inhibition of the AOX pathway limited the generation of the thylakoid ΔpH and suppressed the induction of NPQ. Therefore, the mitochondrial AOX pathway protected the photosynthetic apparatus against photodamage by alleviating the over-reduction of the PSI acceptor side and accelerating the induction of NPQ in Rumex K-1 leaves.

【 授权许可】

Unknown   
© Zhang et al; licensee BioMed Central Ltd. 2012. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.