Ferroni Lorenzo, Živčak Marek, Kovar Marek, Colpo Andrea, Pancaldi Simonetta, Allakhverdiev Suleyman I, Brestič Marian
Laboratory of Plant Cytophysiology, Department of Environmental and Prevention Sciences, University of Ferrara, Ferrara, Italy; Department of Plant Physiology, Slovak University of Agriculture, Nitra, Slovakia.
Department of Plant Physiology, Slovak University of Agriculture, Nitra, Slovakia.
J Photochem Photobiol B. 2022 Sep;234:112549. doi: 10.1016/j.jphotobiol.2022.112549. Epub 2022 Aug 19.
The wheat lines affected by a decrease in the leaf chlorophyll content typically experience a biomass loss. A known major problem of the chlorophyll-deficient wheat mutants is their limited prevention of Photosystem I (PSI) over-reduction brought about by an insufficient cyclic electron flow, potentially exposing them to a higher sensitivity to light fluctuations. However, the resistance of some mutant lines against fluctuating light suggests the occurrence of regulatory processes compensating for the defect in cyclic electron flow. In this study, a phenotyping approach based on fast chlorophyll a fluorescence induction (OJIP transient), corroborated by P700 redox kinetics, was applied to a collection of chlorophyll-deficient wheat lines, grown under continuous or fluctuating light. Quantitative parameters calculated from the OJIP transient are considered informative about Photosystem II (PSII) functional antenna size and photochemistry, as well as the functioning of the entire photosynthetic electron transport chain. The mutants tended to recover a wild-type-like chlorophyll content, and mature plants could hardly be distinguished based on their effective PSII antenna size. Nevertheless, specific OJIP-derived parameters were strongly correlated with the phenotype severity, in particular the amplitude of the I-P phase and the I-P/J-P amplitude ratio, which are indicative of a more capacitive pool of PSI final electron acceptors (ferredoxin and ferredoxin-NADP oxidoreductase, FNR). We propose that the enlargement of such pool of electron carriers is a compensatory response operating at the acceptor side of PSI to alleviate potentially harmful over-reduced states of PSI. Our results also suggest that, in chlorophyll-deficient mutants, higher F /F cannot prove a superior PSII photochemistry and wider I-P phase is not indicative of a higher relative content of PSI.
受叶片叶绿素含量降低影响的小麦品系通常会出现生物量损失。叶绿素缺乏型小麦突变体的一个已知主要问题是，由于循环电子流不足导致光系统I（PSI）过度还原的预防能力有限，这可能使它们对光波动更敏感。然而，一些突变品系对波动光的抗性表明存在补偿循环电子流缺陷的调节过程。在本研究中，一种基于快速叶绿素a荧光诱导（OJIP瞬态）并由P700氧化还原动力学证实的表型分析方法，被应用于在连续光或波动光下生长的一组叶绿素缺乏型小麦品系。从OJIP瞬态计算出的定量参数被认为能提供有关光系统II（PSII）功能天线大小和光化学以及整个光合电子传输链功能的信息。这些突变体倾向于恢复类似野生型的叶绿素含量，成熟植株基于其有效PSII天线大小几乎无法区分。然而，特定的OJIP衍生参数与表型严重程度密切相关，特别是I-P相的振幅和I-P/J-P振幅比，它们表明PSI最终电子受体（铁氧还蛋白和铁氧还蛋白-NADP氧化还原酶，FNR）的电容性更强。我们提出，这种电子载体池的扩大是一种在PSI受体侧起作用的补偿反应，以减轻PSI潜在有害的过度还原状态。我们的结果还表明，在叶绿素缺乏型突变体中，较高的F /F不能证明PSII光化学更优，且较宽的I-P相并不表示PSI的相对含量更高。
