Nezamivand Chegini Saber, Jafarinia Mojtaba, Ghotbi-Ravandi Ali Akbar
Department of Biology, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran.
Department of Plant Sciences and Biotechnology, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran.
Cell Mol Biol (Noisy-le-grand). 2024 Nov 27;70(11):176-184. doi: 10.14715/cmb/2024.70.11.25.
The present study aimed to investigate the impact of progressive drought stress (100%, 75%, 50%, and 25% of field capacity) on photosynthetic light reactions of tomato plants. The imposed drought caused a gradual reduction in leaf RWC leading to a decline in pigment concentration and growth indices. Significant alteration in the OJIP fluorescence transient curves and the formation of specific fluorescence bands (L, K, J, H, and G) gradually increased as drought severity increased. Phenomenological energy fluxes per excited cross-section (ABS/CS, TRo/CS, DIo/CS, ETo/CS and RC/CS) decreased with intensifying drought. As drought stress progressed, JIP-test parameters including The efficiencies of light reactions [φPo/(1- φPo )], the efficiencies of redox reactions [(ψo/(1-ψo)] and the efficiency of PSI to reduce the last electron acceptors [δRo/(1-δRo)] were significantly attenuated. The quantum yields for primary photochemistry (φPo), electron transfer from QA to QB (yO), electron transport (φEo), and reduction of end electron acceptors at the PSI acceptor side (φRo) were negatively affected by drought stress. These results indicate that drought progression leads to structural and functional damage in PSII, characterized by a decrease in active reaction centers, reduced energy absorption and trapping, diminished energetic connectivity within PSII, and inhibition of the oxygen-evolving complex. Additionally, reduced plastoquinone pool size, over-reduction of plastoquinone, and impaired redox state downstream of QB were observed at the donor side of PSII. The quantum yield and efficiency of PSI to reduce electron acceptors were reduced by drought progression. Our results showed that the transcript levels of PetE and PetF genes, encoding the key electron careers plastocyanin and ferredoxin, were significantly downregulated in response to an increase in drought severity, contributing to reduced PSI efficiency. The Transcript levels of PetE and PetF were reduced by 79% and 66% under 25% field capacity treatment, respectively. These results highlight critical points within the photosynthetic apparatus that are highly sensitive to drought, providing valuable insights into the mechanisms of drought-induced damage in tomato plants.
本研究旨在探究渐进性干旱胁迫（田间持水量的100%、75%、50%和25%）对番茄植株光合光反应的影响。施加的干旱导致叶片相对含水量逐渐降低，进而导致色素浓度和生长指标下降。随着干旱严重程度的增加，OJIP荧光瞬态曲线发生显著变化，特定荧光带（L、K、J、H和G）的形成逐渐增加。每个激发截面的现象学能量通量（ABS/CS、TRo/CS、DIo/CS、ETo/CS和RC/CS）随着干旱加剧而降低。随着干旱胁迫的进展，包括光反应效率[φPo/(1 - φPo)]、氧化还原反应效率[(ψo/(1 - ψo)]和PSI还原最终电子受体的效率[δRo/(1 - δRo)]在内的JIP-test参数显著减弱。干旱胁迫对初级光化学量子产率（φPo）、从QA到QB的电子转移（yO）、电子传递（φEo）以及PSI受体侧最终电子受体的还原（φRo）产生负面影响。这些结果表明，干旱进展导致PSII的结构和功能受损，其特征是活性反应中心减少、能量吸收和捕获降低、PSII内的能量连接性减弱以及氧释放复合体受到抑制。此外，在PSII的供体侧观察到质体醌库大小减小、质体醌过度还原以及QB下游的氧化还原状态受损。干旱进展降低了PSI还原电子受体的量子产率和效率。我们的结果表明，编码关键电子载体质体蓝素和铁氧还蛋白的PetE和PetF基因的转录水平随着干旱严重程度的增加而显著下调，导致PSI效率降低。在田间持水量25%的处理下，PetE和PetF基因的转录水平分别降低了79%和66%。这些结果突出了光合装置中对干旱高度敏感的关键点，为番茄植株干旱诱导损伤的机制提供了有价值的见解。
