Roles of the Cyclic Electron Flow Around PSI (CEF-PSI) and O2-Dependent Alternative Pathways in Regulation of the Photosynthetic Electron Flow in Short-Term Fluctuating Light in Arabidopsis thaliana
Roles of the Cyclic Electron Flow Around PSI (CEF-PSI) and O2-Dependent Alternative Pathways in Regulation of the Photosynthetic Electron Flow in Short-Term Fluctuating Light in Arabidopsis thaliana
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DOI：
10.1093/pcp/pcu033
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发表时间：
2014-05-01
影响因子：
4.9
通讯作者：
Terashima, Ichiro
中科院分区：
文献类型：
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作者：
Kono, Masaru;Noguchi, Ko;Terashima, Ichiro
为了评价PSI周围的循环电子流(CEF-PSI)和包括水-水循环在内的依赖O2的交替途径在波动光中的作用，我们在恒定光下培养了野生型和pgr5突变体拟南芥，并测量了在240(HL)和30A moL光强m(-2)S(-2)(Ll)每隔2min的波动光下其叶片的Chl荧光和P700参数。在20%O-2时，PSII的光化学量子效率在波动光处理开始后不久下降，特别是在pgr5植株中。这种处理42min对pgr5植株的PSI有明显的光抑制作用。在野生型中也观察到轻微的PSI光抑制。我们测量了PSII和PSI之间的能量分享，并估计了PSI和PSII的电子传输速率(ETRs)。PGR5显示较大的能量分配给PSI。与野生型相比，在20%O-2时，由于PSI受体侧的限制，pgr5的PSI/PSII ETR的比率在LL较高，而在HL较低。在2.7%或0%O-2时，pgr5植株的CEF-PSI增强，PSI电子流的受体侧限制被释放，没有观察到PSI光抑制。结果表明，光波动对PSI是一种强有力的胁迫，而CEF-PSI对于保护PSI免受这种胁迫是必不可少的。
To assess the roles of the cyclic electron flow around PSI (CEF-PSI) and O-2-dependent alternative pathways including the water-water cycle in fluctuating light, we grew the wild type and pgr5 mutant of Arabidopsis thaliana in constant light, and measured Chl fluorescence and P700 parameters in their leaves in the fluctuating light alternating between 240 (HL) and 30 A mu mol photons m(-2) s(-2) (LL) every 2 min. At 20% O-2, the photochemical quantum yield of PSII decreased, in particular in the pgr5 plants, soon after the start of the fluctuating light treatment. PSI of the pgr5 plants was markedly photoinhibited by this treatment for 42 min. Slight PSI photoinhibition was also observed in the wild type. We measured energy sharing between PSII and PSI and estimated the PSI and PSII electron transport rates (ETRs). pgr5 showed larger energy allocation to PSI. In contrast to the wild type, the ratio of the PSI to the PSII ETR in pgr5 was higher in LL but lower in HL at 20% O-2 due to PSI acceptor-side limitation. At 2.7% or 0% O-2, the CEF-PSI of the pgr5 plants was enhanced, the acceptor-side limitation of PSI electron flow was released and PSI photoinhibition was not observed. The results suggest that the light fluctuation is a potent stress to PSI and that the CEF-PSI is essential to protect PSI from this stress.