Abstract

Effect of UV-A radiation (10 W/m², 2 h) and modifying effect of brief exposure to red light (RL) (1.8 W/m², 20 min) on photochemical activity of photosystem II (PSII) (F_v/F_m), as well as on activity of ascorbate peroxidase (AsP) and phenylalanine ammonia-lyase (PAL), were investigated in the leaves of 26–28-day-old Аrabidopsis thaliana (L.) Heynh. plants of wild type (WT) and mutants: hy3 deficient in phytochrome B (phyB) and hy2 defective in phytochromobilin synthesis. UV-A reduced photochemical activity of PSII and activities of AsP and PAL. Exposure to RL increased PAL activity in only WT plants and in mutant hy3. Elevation of expression of genes APX1, sAPX, tAPX, and PAL encoding enzymes AsP and PAL was detected upon the exposure to RL and UV-A. For instance, expression of gene APX1 in WT plants and in mutant hy3 rose upon exposure to RL and UV-A; in mutant hy2, it increased only upon UV-A treatment. Expression of gene tAPX in WT plants rose only under the effect of RL, whereas expression of gene sAPX did not rise in any type of treatment. In mutant hy2, expression of the above-named genes decreased upon the effect of RL. Upon joint action of RL and UV-A (RL followed by UV), the negative effect of UV-A on the activity of the total pool of AsP was nullified by RL in only WT plants and in mutant hy3. Partial removal of the negative effect of UV-A on activity of PSII as a result of pretreatment of plants with RL is probably related to a rise in the activity of antioxidant enzymes. This is evident in WT plants whose PSII is more sensitive to RL radiation than in mutants deficient in phytochromes. We believe that PSII resistance to UV-A radiation depends on the potential of the plant antioxidant system, which rises when the share of the active form of phytochrome in its total pool increases as a result of plants’ pretreatment with RL and is partially realized by way of induction of transcriptional activity of antioxidant genes.

中文翻译：

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植物色素缺乏对抗UV-A和红光照射下拟南芥植物叶片抗坏血酸过氧化物酶和苯丙氨酸氨化酶活性及APX1，tAPX，sAPX和PAL基因表达的影响

摘要

UV-A辐射（10瓦/米的效果²，2小时）和修改短暂暴露的效果为红色光（RL）（1.8瓦/米²的光系统II（PSII）（的光化学活性，20分钟）˚F _v / F _m）以及抗坏血酸过氧化物酶（AsP）和苯丙氨酸氨裂合酶（PAL）的活性，在26–28天大的拟南芥（L.）Heynh的叶片中进行了研究。野生型（WT）和突变体的植物：hy3缺乏植物色素B（phyB），hy2缺乏植物叶绿素合成。UV-A降低了PSII的光化学活性以及AsP和PAL的活性。暴露于RL仅在野生植物和突变体hy3中增加了PAL活性。暴露于RL和UV-A后，检测到基因APX1， sAPX， tAPX和PAL编码酶AsP和PAL的表达升高。例如，暴露于RL和UV-A后，WT植物和突变体hy3中APX1基因的表达上升。在突变体hy2中，它仅在UV-A处理后增加。WT植物中tAPX基因的表达仅在RL的作用下增加，而sAPX基因的表达在任何处理中均未升高。在hy2突变体中RL的作用使上述基因的表达降低。在RL和UV-A共同作用下（RL随后是UV），仅在野生植物和突变体hy3中，UV消除了UV-A对AsP总库活性的负面影响。。用RL预处理植物后，部分消除UV-A对PSII活性的负面影响可能与抗氧化酶活性的提高有关。这在其PSII对RL辐射比缺乏植物色素的突变体的WT植物中更为明显。我们认为PSII对UV-A辐射的抗性取决于植物抗氧化剂系统的潜力，当植物进行RL预处理后，当植物总活性物质中植物色素的活性形式所占份额增加时，PSII的潜力就会增加，并且可以通过以下方式部分实现：抗氧化剂基因转录活性的诱导方法。