Department of Botany, University of Delhi, 110007, India.
Department of Botany, University of Delhi, 110007, India.
Nitric Oxide. 2020 Apr 1;97:33-47. doi: 10.1016/j.niox.2020.01.014. Epub 2020 Feb 8.
The present study unravels origin of nitric oxide (NO) and the interaction between 24-Epibrassinolide (EBL) and nitrate reductase (NR) for NO production in Indian mustard (Brassica juncea L.) under salinity stress. Two independent experiments were performed to check whether (i) Nitrate reductase or Nitric oxide synthase takes part in the biosynthesis of endogenous NO and (ii) EBL has any regulatory effect on NR-dependent NO biosynthesis in the alleviation of salinity stress. Results revealed that NR-inhibitor tungstate significantly (P ≤ 0.05) decreased the NR activity and endogenous NO content, while NOS inhibitor l-NAME did not influence NO biosynthesis and plant growth. Under salinity stress, inhibition in NR activity decreased the activities of antioxidant enzymes, increased HO, MDA, protein carbonyl content and caused DNA damage, implying that antioxidant defense might be related to NO signal. EBL supplementation enhanced the NR activity but did not influence NOS activity, suggesting that NR was involved in endogenous NO production. EBL supplementation alleviated the inhibitory effects of salinity stress and improved the plant growth by enhancing nutrients, photosynthetic pigments, compatible osmolytes, and performance of AsA-GSH cycle. It also decreased the superoxide ion accumulation, leaf epidermal damages, cell death, DNA damage, and ABA content. Comet assay revealed significant (P ≤ 0.05) enhancement in tail length and olive tail moment, while flow cytometry did not showed any significant (P ≤ 0.05) changes in genome size and ploidy level under salinity stress. Moreover, EBL supplementation increased the G6PDH activity and S-nitrosothiol content which further boosted the antioxidant responses under salinity stress. Taken together, these results suggested that NO production in mustard occurred in NR-dependent manner and EBL in association with endogenous NO activates the antioxidant system to counter salinity stress.
本研究揭示了一氧化氮（NO）的起源以及 24-表油菜素内酯（EBL）与硝酸还原酶（NR）之间的相互作用，以研究盐胁迫下印度芥菜（Brassica juncea L.）中 NO 的产生。进行了两项独立的实验，以检查（i）硝酸还原酶或一氧化氮合酶是否参与内源性 NO 的生物合成，以及（ii）EBL 是否对缓解盐胁迫过程中 NR 依赖性 NO 生物合成具有任何调节作用。结果表明，硝酸盐还原酶抑制剂钨酸钠显著（P≤0.05）降低了 NR 活性和内源性 NO 含量，而一氧化氮合酶抑制剂 l-NAME 不影响 NO 生物合成和植物生长。在盐胁迫下，NR 活性的抑制降低了抗氧化酶的活性，增加了 HO、MDA、蛋白质羰基含量并导致 DNA 损伤，这表明抗氧化防御可能与 NO 信号有关。EBL 补充增强了 NR 活性，但不影响 NOS 活性，表明 NR 参与了内源性 NO 的产生。EBL 补充缓解了盐胁迫的抑制作用，并通过增强养分、光合色素、相容性渗透物和 ASA-GSH 循环的性能来改善植物生长。它还减少了超氧阴离子的积累、叶片表皮损伤、细胞死亡、DNA 损伤和 ABA 含量。彗星试验显示，尾巴长度和橄榄尾矩显著（P≤0.05）增加，而流式细胞术在盐胁迫下未显示基因组大小和倍性水平有任何显著变化（P≤0.05）。此外，EBL 补充增加了 G6PDH 活性和 S-亚硝基硫醇含量，这进一步增强了盐胁迫下的抗氧化反应。总之，这些结果表明，芥菜中的 NO 产生是依赖于 NR 的方式，EBL 与内源性 NO 一起激活抗氧化系统以应对盐胁迫。
