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Calcium and Calmodulin Are Involved in Nitric Oxide-Induced Adventitious Rooting of Cucumber under Simulated Osmotic Stress.

ABSTRACT: Osmotic stress is a major form of abiotic stress that adversely affects growth and development of plants and subsequently reduces yield and quality of crops. In this study, the effect of nitric oxide (NO) and calcium (Ca²⁺) on the process of adventitious rooting in cucumber (Cucumis sativus L.) under simulated osmotic stress was investigated. The results revealed that the effect of exogenous NO and Ca²⁺ in promoting the development of adventitious roots in cucumber seedlings under simulated osmotic stress was dose-dependent, with a maximal biological response at 10 μM NO donor nitroprusside (SNP) or 200 μM Ca²⁺. The application of Ca²⁺ chelators or channel inhibitors and calmodulin (CaM) antagonists significantly reversed NO-induced adventitious rooting, implying that endogenous Ca²⁺/CaM might be involved in NO-induced adventitious rooting under osmotic stress. Moreover, intracellular Ca amount was also increased by NO in cucumber hypocotyls during the development of adventitious roots under osmotic stress. This increase of endogenous Ca²⁺ was inhibited by NO specific scavenger 2-(4-carboxyphenyl) -4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO), nitrate reductase inhibitors tungstate (Na₂WO₄) and sodium azide (NaN₃)_. This gives an indication that Ca²⁺ might be a downstream signaling molecule in the adventitious root development by NO under osmotic condition. The results also show that NO or Ca²⁺ play a positive role in improving plant water status and photosynthetic system by increasing chlorophyll content and photochemical activity in leaves. Furthermore, NO and Ca²⁺ treatment might alleviate the negative effects of osmotic stress by decreasing membrane damage and reactive oxygen species (ROS) production by enhancing the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). Therefore, Ca²⁺/CaM may act as a downstream signaling molecule in NO-induced development of adventitious root under simulated osmotic stress through improving the photosynthetic performance of leaves and activating antioxidative system in plants.

SUBMITTER: Niu L

PROVIDER: S-EPMC5623940 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Nitric oxide (NO) acts an essential signaling molecule that is involved in regulating various physiological and biochemical processes in plants. However, whether S-nitrosylation is a crucial molecular mechanism of NO is still largely unknown. In this study, 50 ?M S-nitrosoglutathione (GSNO) treatment was found to have a maximum biological effect on promoting adventitious rooting in cucumber. Meanwhile, removal of endogenous NO significantly inhibited the development of adventitious roots implying that NO is responsible for promoting the process of adventitious rooting. Moreover, application of GSNO resulted in an increase of intracellular S-nitrosothiol (SNO) levels and endogenous NO production, while decreasing the S-nitrosoglutathione reductase (GSNOR) activity during adventitious rooting, implicating that S-nitrosylation might be involved in NO-induced adventitious rooting in cucumber. Furthermore, the identification of S-nitrosylated proteins was performed utilizing the liquid chromatography/mass spectrometry/mass spectrometry (LC-MS/MS) and biotin-switch technique during the development of adventitious rooting. Among these proteins, the activities and S-nitrosylated level of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), tubulin alpha chain (TUA), and glutathione reductase (GR) were further analyzed as NO direct targets. Our results indicated that NO might enhance the S-nitrosylation level of GAPDH and GR, and was found to subsequently reduce these activities and transcriptional levels. Conversely, S-nitrosylation of TUA increased the expression level of TUA. The results implied that S-nitrosylation of key proteins seems to regulate various pathways through differential S-nitrosylation during adventitious rooting. Collectively, these results suggest that S-nitrosylation could be involved in NO-induced adventitious rooting, and they also provide fundamental evidence for the molecular mechanism of NO signaling during adventitious rooting in cucumber explants.

Project description:Abscisic acid (ABA) affects many important plant processes, such as seed germination, root elongation and stomatal movement. However, little information is available about the relationship between ABA and sugar synthesis during adventitious root formation. The aim of this study was to evaluate the effect of ABA on adventitious root formation in cucumber and whether the effect of this plant hormone on sugar synthesis could be included as a causative factor for adventitious root development. We determined the contents of glucose, sucrose, starch, total sugar and sugar-related enzymes, including sucrose synthase (SS), sucrose phosphate synthase (SPS), hexokinase (HK) and pyruvate kinase (PK) activities in ABA treatment. We also quantified the relative expression of sucrose or glucose synthesis genes during this process. Increasing ABA concentrations significantly improved adventitious root formation, with the most considerable effect at 0.05 μM. Compared to the control, ABA treatment showed higher glucose, sucrose, starch and total sugar contents. Moreover, ABA treatment increased glucose-6-phosphate (G6P), fructose-6-phosphate (F6P) and glucose-1-phosphate (G1P) contents in cucumber explants during adventitious root development, which was followed by an increase of activities of sucrose-related enzymes SS and SPS, glucose-related enzymes HK and PK. ABA, meanwhile, upregulated the expression levels of sucrose or glucose synthesis-related genes, including CsSuSy1, CsSuSy6, CsHK1 and CsHK3. These results suggest that ABA may promote adventitious root development by increasing the contents of glucose, sucrose, starch, total sugar, G6P, F6P and G1P, the activities of SS, SPS, HK, SPS and the expression levels of CsSuSy1, CsSuSy6, CsHK1 and CsHK3 genes. These findings provide evidence for the physiological role of ABA during adventitious root formation and provide a new understanding of the possible relationship between ABA and sugar synthesis during adventitious rooting in plants.

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Calcium and Calmodulin Are Involved in Nitric Oxide-Induced Adventitious Rooting of Cucumber under Simulated Osmotic Stress.

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