Analysis of regulating factor of photosynthesis by two-dimensional fluorescence screening

虽然光对植物的生存是不可或缺的，但过多的光会导致产生活性氧物种，从而损害光合作用装置。为了避免这种损害，植物进化出了多种机制，在转换到强光时下调光合作用电子传递。为了找出在HL条件下调节光合作用电子传递初始激活的关键蛋白，我们通过12秒的叶绿素荧光动力学筛选，分离到了一个拟南芥突变体cfa1(叶绿素荧光改变)。用脉冲放大调制系统测量叶绿素荧光表明，无论是在750μE/m2s(HL)的强光条件下还是在80μE/m2s(L1)的生长光条件下，cfa1突变体的稳态光合作用参数都不能与Wt区分。然而，非光化学猝灭(NPQ)和光化学猝灭(QP)的时间进程表明，与WT相比，HL对cfa1突变体NPQ和QP的诱导延迟。在250μE/m2光照条件下，突变体的生长速度慢于WT，这种表型特征在较高光照条件下增强。有趣的是，在250με/m2s的强光条件下生长的Cfa1突变体的NPQ和QP的诱导即使在L1下也延迟了。这些结果表明，CFA1可能不仅参与了光合作用电子传递的初始激活，而且还参与了对强光的适应。T-DNA插入位点位于叶绿体转运肽和羧基肽酶A为基序的未知蛋白质的5‘端非编码区，对cfa1突变体的进一步研究将揭示强光条件下电子传递反应的调控机制。

Although light is indispensable for plants survival, excessive light can lead to produce active oxygen species, giving damage to the photosynthetic apparatus. In order to avoid this damage, plants have evolved multiple mechanisms that down-regulate photosynthetic electron transport upon the shift to high light. To find out the key proteins that regulate the initial activation of photosynthetic electron transport under HL condition, we isolated an Arabidopsis mutant, cfa1 (chlorophyll fluorescence alteration), by the screening based on the kinetics of chlorophyll fluorescence for 12 seconds. Measurement of chlorophyll fluorescence by pulse amplified modulating system (PAM) showed that none of the photosynthetic parameters in the steady state were distinguishable between the cfa1 mutant and WT either under high light condition at 750 μE/m2s (HL) or under growth light condition at 80 μE/m2s (LL). However, time course of non photochemical quenching (NPQ) and photochemical quenching (qP) indicated that induction of NPQ and qP delayed in the cfa1 mutant when exposed to HL compared to those of WT. This phenatypic character was enhanced in the plants grown under higher light condition at 250 μE/m2s, where the mutants grew slower than WT. Interestingly, induction of NPQ and qP of the cfa1 mutant grown under higher light condition at 250 με/m2s delayed even under LL. These results suggest that CFA1 may be involved not only in the initial activation of photosynthetic electron transport upon the shift to HL but also in acclimation to high light. The site of T-DNA insertion was on 5'-UTR of unknown protein having motifs of chloroplast transit peptide and of carboxypeptidase A. Further study of the cfa1 mutant should reveal the regulatory mechanism of the response of electron transport to high light condition.