Contrasting Responses to Stress Displayed by Tobacco Overexpressing an Algal Plastid Terminal Oxidase in the Chloroplast
Contrasting Responses to Stress Displayed by Tobacco Overexpressing an Algal Plastid Terminal Oxidase in the Chloroplast
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DOI：
10.3389/fpls.2020.00501
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发表时间：
2020-04-28
影响因子：
5.6
通讯作者：
Nixon, Peter J.
中科院分区：
文献类型：
--
作者：
Ahmad, Niaz;Khan, Muhammad Omar;Nixon, Peter J.
质体末端氧化酶（PTOX）-一种在叶绿体类囊体膜中发现的界面二铁羧酸盐蛋白-氧化质体醌醇并将分子氧还原为水。它被认为在某些植物物种对光和盐（NaCl）胁迫的响应中发挥重要的生理作用，通过将过量的电子转移到氧，从而保护光系统II（PSII）免受光损伤。因此，PTOX是在作物植物中工程化胁迫耐受性的候选者。先前，我们使用叶绿体转化技术在烟草中过量表达来自绿色莱茵衣藻的PTOX 1（产生系Nt-PTOX-OE）。与预期相反，Nt-PTOX-OE植物的生长对光胁迫更敏感。在这里，我们详细研究了PTOX 1对生长在两种不同光照强度下的Nt-PTOX-OE烟草植物光合作用的影响。在“弱光”（50 μ mol photons m（-2）s（-1））条件下，Nt-PTOX-OE和WT植株表现出相似的光合活性。相比之下，在“强光”（125 μ mol光子m（-2）s（-1））条件下，Nt-PTOX-OE表现出比WT更低的PSII活性，而光系统I（PSI）活性不受影响。在强光下生长的Nt-PTOX-OE也未能增加叶绿素a/B比和CO2同化的最大速率相比，低光生长的植物，这表明在驯化的缺陷。相比之下，Nt-PTOX-OE植物表现出更好的发芽，根长，地上部生物量的积累比野生型暴露于高水平的NaCl时，表现出更好的恢复和更少的叶绿素漂白NaCl胁迫后，水培生长。总的来说，我们的研究结果加强了PTOX和植物对盐胁迫的抗性之间的联系。
The plastid terminal oxidase (PTOX) - an interfacial diiron carboxylate protein found in the thylakoid membranes of chloroplasts - oxidizes plastoquinol and reduces molecular oxygen to water. It is believed to play a physiologically important role in the response of some plant species to light and salt (NaCl) stress by diverting excess electrons to oxygen thereby protecting photosystem II (PSII) from photodamage. PTOX is therefore a candidate for engineering stress tolerance in crop plants. Previously, we used chloroplast transformation technology to over express PTOX1 from the green alga Chlamydomonas reinhardtii in tobacco (generating line Nt-PTOX-OE). Contrary to expectation, growth of Nt-PTOX-OE plants was more sensitive to light stress. Here we have examined in detail the effects of PTOX1 on photosynthesis in Nt-PTOX-OE tobacco plants grown at two different light intensities. Under 'low light' (50 mu mol photons m(-2) s(-1)) conditions, Nt-PTOX-OE and WT plants showed similar photosynthetic activities. In contrast, under 'high light' (125 mu mol photons m(-2) s(-1)) conditions, Nt-PTOX-OE showed less PSII activity than WT while photosystem I (PSI) activity was unaffected. Nt-PTOX-OE grown under high light also failed to increase the chlorophyll a/b ratio and the maximum rate of CO2 assimilation compared to low-light grown plants, suggesting a defect in acclimation. In contrast, Nt-PTOX-OE plants showed much better germination, root length, and shoot biomass accumulation than WT when exposed to high levels of NaCl and showed better recovery and less chlorophyll bleaching after NaCl stress when grown hydroponically. Overall, our results strengthen the link between PTOX and the resistance of plants to salt stress.