Li Xin-Guo, Duan Wei, Meng Qing-Wei, Zou Qi, Zhao Shi-Jie
College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong, 271018, P.R. China.
Plant Cell Physiol. 2004 Jan;45(1):103-8. doi: 10.1093/pcp/pch011.
The function of chloroplastic NAD(P)H dehydrogenase (NDH) was examined by comparing a tobacco transformant (DeltandhB) in which the ndhB gene had been disrupted with its wild type, upon exposure to chilling temperature (4 degrees C) under low irradiance (100 micro mol m(-2) s(-1) PFD). During the chilling stress, the maximum photochemical efficiency of PSII (F(v)/F(m)) decreased markedly in both the wild type and DeltandhB. However, both F(v)/F(m) and P700(+), as well as the PSII-driven electron transport rate (ETR), in DeltandhB were lower than that in the wild type, implying that NDH-dependent cyclic electron flow around PSI functioned to protect the photosynthetic apparatus from chilling stress under low irradiance. Under the stress, non-photochemical quenching (NPQ), particularly the fast relaxing NPQ component (qf) and the de-epoxidized ratio of the xanthophyll cycle pigments, (A+Z)/(V+A+Z), were distinguishable in DeltandhB from those in the wild type. The lower NPQ in DeltandhB might be related to an inefficient proton gradient across thylakoid membranes (DeltapH) because of lacking an NDH-dependent cyclic electron flow around PSI at chilling temperature under low irradiance.
通过比较在低光照（100微摩尔·米⁻²·秒⁻¹光合光子通量密度）下暴露于低温（4摄氏度）时，ndhB基因被破坏的烟草转化体（DeltandhB）及其野生型，研究了叶绿体NAD(P)H脱氢酶（NDH）的功能。在冷胁迫期间，野生型和DeltandhB中PSII的最大光化学效率（F(v)/F(m)）均显著下降。然而，DeltandhB中的F(v)/F(m)、P700⁺以及PSII驱动的电子传递速率（ETR）均低于野生型，这意味着围绕PSI的NDH依赖型循环电子流在低光照下的冷胁迫中起到保护光合机构的作用。在胁迫下，DeltandhB中的非光化学猝灭（NPQ），特别是快速弛豫的NPQ组分（qf）以及叶黄素循环色素的脱环氧化率（(A + Z)/(V + A + Z)）与野生型有所不同。DeltandhB中较低的NPQ可能与由于在低温低光照下缺乏围绕PSI的NDH依赖型循环电子流而导致的类囊体膜两侧质子梯度（ΔpH）效率低下有关。
