Nitric oxide mediates the fungal elicitor-induced puerarin biosynthesis in Pueraria thomsonii Benth. suspension cells through a salicylic acid (SA)-dependent and a jasmonic acid (JA)-dependent signal pathway

Nitric oxide (NO) has emerged as a key signaling molecule in plant secondary metabolite biosynthesis recently. In order to investigate the molecular basis of NO signaling in elicitor-induced secondary metabolite biosynthesis of plant cells, we determined the contents of NO, salicylic acid (SA), jasmonic acid (JA), and puerarin in Pueraria thomsonii Benth. suspension cells treated with the elicitors prepared from cell walls of Penicillium citrinum. The results showed that the fungal elicitor induced NO burst, SA accumulation and puerarin production of P. thomsonii Benth. cells. The elicitor-induced SA accumulation and puerarin production was suppressed by nitric oxide specific scavenger cPITO, indicating that NO was essential for elicitor-induced SA and puerarin biosynthesis in P. thomsonii Benth. cells. In transgenic NahG P. thomsonii Benth. cells, the fungal elicitor also induced puerarin biosynthesis, NO burst, and JA accumulation, though the SA biosynthesis was impaired. The elicitor-induced JA accumulation in transgenic cells was blocked by cPITO, which suggested that JA acted downstream of NO and its biosynthesis was controlled by NO. External application of NO via its donor sodium nitroprusside (SNP) enhanced puerarin biosynthesis in transgenic NahG P. thomsonii Benth. cells, and the NO-triggered puerarin biosynthesis was suppressed by JA inhibitors IBU and NDGA, which indicated that NO induced puerarin production through a JA-dependent signal pathway in the transgenic cells. Exogenous application of SA suppressed the elicitor-induced JA biosynthesis and reversed the inhibition of IBU and NDGA on elicitor-induced puerarin accumulation in transgenic cells, which indicated that SA inhibited JA biosynthesis in the cells and that SA might be used as a substitute for JA to mediate the elicitor-and NO-induced puerarin biosynthesis. It was, therefore, concluded that NO might mediate the elicitor-induced puerarin biosynthesis through SA-and JA-dependent signal pathways in wildtype P. thomsonii Benth. cells and transgenic NahG cells respectively.     

Nitric oxide mediates the fungal elicitor-induced puerarin biosynthesis in Pueraria thomsonii Benth. suspension cells through a salicylic acid (SA)-dependent and a jasmonic acid (JA)-dependent signal pathway

Higher plants constitute one of our most important natural resources, which provide not only foodstuffs, fibers, and woods, but also many chemicals, such as flavorings, dyes, and pharmaceuticals. Although plants are renewable resources, some species are b…     

南美斑潜蝇幼虫为害对黄瓜叶片中水杨酸和茉莉酸的诱导作用

【目的】为揭示南美斑潜蝇Liriomyza huidobrensis (Blanchard)与其寄主相互作用的机理, 为利用诱导抗性控制南美斑潜蝇的发生为害奠定必要的基础。【方法】本文采用高效液相色谱法（HPLC）和超高效液相色谱法-质谱联用法（UPLC MS）, 分别测定了南美斑潜蝇幼虫为害对黄瓜叶片中茉莉酸（jasmonic acid, JA）和水杨酸（salicylic acid, SA）的诱导作用。【结果】南美斑潜蝇幼虫持续为害1 d后, 受害黄瓜叶片内JA含量即显著高于健康对照, 轻度受害处理和重度受害处理分别在第3天和第5天上升幅度最大, 分别比健康对照增加2.01倍和1.62倍; 而SA含量在3 d后才显著高于健康对照, 轻度受害处理和重度受害处理在第9天上升幅度最大, 分别比健康对照增加4.66倍和1.67倍; 轻度受害对JA和SA的系统诱导作用不明显, 而重度受害对JA和SA具有明显的系统诱导作用。【结论】南美斑潜蝇幼虫为害对黄瓜叶片内JA和SA具有诱导作用。     

水杨酸对黄瓜幼苗抗高温胁迫能力的影响

对津绿2号黄瓜四叶期的幼苗分别喷施0、50、100和200μmol·L-1的水杨酸(SA)溶液,24h后以42℃的高温胁迫24h。结果表明:不同浓度的SA溶液均可降低黄瓜叶片中的相对电导率和丙二醛(MDA)含量,增加SOD活性,以50μmol·L-1的效果最优。但相对电导率和MDA含量的降幅及SOD活性的增幅则随SA浓度的增加而减小。     

水杨酸对黄瓜幼苗壮苗的形成及抗低温胁迫能力的生理效应

用一定浓度的ＳＡ溶液喷布黄瓜幼苗,结果表明,ＳＡ可显著提高黄瓜幼苗的壮苗 数,促进壮苗的形成,ＳＡ的最佳深度为２５０ｍｇ．Ｌ＾－１。同时,当低温胁地,２５０ｍｇ．ｌ＾１－的ＳＡ可显著提高黄瓜幼苗叶片细胞膜的千钧一发生,抑制叶片中ＭＤＡ的累积。     

Interaction between abscisic acid and nitric oxide in PB90‐induced catharanthine biosynthesis of catharanthus roseus cell suspension cultures

Elicitations are considered to be an important strategy to improve production of secondary metabolites of plant cell cultures. However, mechanisms responsible for the elicitor‐induced production of secondary metabolites of plant cells have not yet been fully elucidated. Here, we report that treatment of Catharanthus roseus cell suspension cultures with PB90, a protein elicitor from Phytophthora boehmeriae, induced rapid increases of abscisic acid (ABA) and nitric oxide (NO), subsequently followed by the enhancement of catharanthine production and up‐regulation of Str and Tdc, two important genes in catharanthine biosynthesis. PB90‐induced catharanthine production and the gene expression were suppressed by the ABA inhibitor and NO scavenger respectively, showing that ABA and NO are essential for the elicitor‐induced catharanthine biosynthesis. The relationship between ABA and NO in mediating catharanthine biosynthesis was further investigated. Treatment of the cells with ABA triggered NO accumulation and induced catharanthine production and up‐regulation of Str and Tdc. ABA‐induced catharanthine production and gene expressions were suppressed by the NO scavenger. Conversely, exogenous application of NO did not stimulate ABA generation and treatment with ABA inhibitor did not suppress NO‐induced catharanthine production and gene expressions. Together, the results showed that both NO and ABA were involved in PB90‐induced catharanthine biosynthesis of C. roseus cells. Furthermore, our data demonstrated that ABA acted upstream of NO in the signaling cascade leading to PB90‐induced catharanthine biosynthesis of C. roseus cells. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:994–1001, 2013     

Arbuscular mycorrhizal fungal inoculation increases phenolic synthesis in clover roots via hydrogen peroxide,salicylic acid and nitric oxide signaling pathways

Arbuscular mycorrhizal fungi can increase the host resistance to pathogens via promoted phenolic synthesis, however, the signaling pathway responsible for it still remains unclear. In this study, in order to reveal the signaling molecules involved in this process, we inoculated Trifolium repense L. with an arbuscular mycorrhizal fungus (AMF), Glomus mosseae, and monitored the contents of phenolics and signaling molecules (hydrogen peroxide (H₂O₂), salicylic acid (SA), and nitric oxide (NO)) in roots, measured the activities of l-phenylalanine ammonia-lyase (PAL) and nitric oxide synthase (NOS), and the expression of pal and chs genes. Results demonstrated that AMF colonization promoted the phenolic synthesis, in parallel with the increase in related enzyme activity and gene expression. Meanwhile, the accumulation of all three signaling molecules was also up-regulated by AMF. This study suggested that AMF increased the phenolic synthesis in roots probably via signaling pathways of H₂O₂, SA and NO in a signaling cascade.     

Exploring the regulatory role of nitric oxide (NO) and the NO-p38MAPK/cGMP pathway in larval settlement of the bryozoan Bugula neritina

The bryozoan Bugula neritina is a cosmopolitan marine fouling species that causes major fouling problems in sub-tropical waters. Settlement of B. neritina larvae can be triggered without an obvious external cue. Here, the negative regulatory role of nitric oxide (NO) during larval settlement of B. neritina was demonstrated to be mediated by cyclic guanosine monophosphate (cGMP). Although the regulatory role of the NO-p38 MAPK signaling axis in larval settlement was not evident, inhibition of nitric oxide synthase (NOS) led to the deactivation of p38 MAPK. Exclusive localization of NO and NO signaling components in sensory-related organs of the larvae is consistent with its signal transduction function in metamorphosis. Overall, this study provides new insights into the regulatory roles of the NO-p38MAPK/cGMP pathway in B. neritina settlement.     

The role of nitric oxide in delta-aminolevulinic acid (ALA)-induced photosensitivity of cancerous cells

Application of delta-aminolevulinic acid (ALA) results in the endogenous accumulation of protoporphyrin IX and is a useful approach in the photodynamic therapy (PDT) of cancers. To investigate the role of nitric oxide (NO) in the specific accumulation of protoporphyrin and ALA-induced PDT of cancerous cells, we transfected inducible-nitric oxide synthase (NOS2) cDNA into human embryonic kidney (HEK) 293T cells and examined the ALA-induced photo-damage as well as the accumulation of porphyrin in the cells. When the NOS2-expressing HEK293T cells were treated with ALA and then exposed to visible light, they became more sensitive to the light with accumulating porphyrins, as compared with the ALA-treated control cells. An increase in the generation of NO in transfected cells led to the accumulation of protoporphyrin with a concomitant decrease of ferrochelatase, the final step enzyme of heme biosynthesis. When mouse macrophage-like RAW264.7 cells were cultured with lipopolysaccharide and interferon-gamma, the expression of NOS2 was induced. The addition of ALA to these cells led to the accumulation of protoporphyrin and cell death upon exposure to light. The treatment of cells with an NOS inhibitor, NG-monomethyl-L-arginine acetate, resulted in the inhibition of protoporphyrin accumulation and cell death. The levels of mitochondrial ferrochelatase and rotenone-sensitive NADH dehydrogenase in the NOS2-induced cells decreased. These results indicated that the generation of NO augments the ALA-induced accumulation of protoporphyrin IX and subsequent photo-damage in cancerous cells by decreasing the levels of mitochondrial iron-containing enzymes. Based on the fact that the production of NO in cancerous cells is elevated, NO in the cells is responsible for susceptibility with ALA-induced PDT.     

Nitric oxide imbalance provokes a nitrosative response in plants under abiotic stress

Nitric oxide (NO), a free radical generated in plant cells, belongs to a family of related molecules designated as reactive nitrogen species (RNS). When an imbalance of RNS takes place for any adverse environmental circumstances, some of these molecules can cause direct or indirect damage at the cellular or molecular level, promoting a phenomenon of nitrosative stress. Thus, this review will emphasize the recent progress in understanding the function of NO and its production under adverse environmental conditions.     

Expression profile of jasmonic acid-induced genes and the induced resistance against the root-knot nematode (Meloidogyne incognita) in tomato plants (Solanum lycopersicum) after foliar treatment with methyl jasmonate

We investigated what gene(s) in the plant roots have the positive role against repressing root-knot nematode (RKN) infection. We investigated the interaction between RKN infection and gene expression in the plant roots induced by methyl jasmonate (MeJA). We focused on the induced resistance response and the duration after foliar treatment with MeJA of 0.1, 0.5, 1.0, and 5.0mM at 1, 24, 48, and 72h prior to the inoculation of RKN. As a result, the foliar treatment with MeJA at 0.5mM or higher concentrations significantly reduced the infection of RKN in plants and the effect lasted for about 1 week. The repressing effect on RKN population declined to the lowest level in two weeks after MeJA treatment. The expression of proteinase inhibitors (PIs) and multicystatin (MC) were induced while the repressing effect on RKN was valid and a negative correlation was found between the expression of PIs or MC and RKN infection. In addition, when tomato plants no longer expressing MC and PIs were treated again with MeJA, the repressing effect revived. These phenomena appeared to be regardless of the existence of Mi-genes or isolate of RKN. Our results indicate that the expression level of MC and PIs may be effective as marker genes for estimating the induced resistance response against RKN infection.     

The message of nitric oxide in cadmium challenged plants

During the last decade it has been found that cadmium (Cd), one of the most toxic elements occurring in polluted environments, interferes with nitric oxide (NO), a multifunctional signaling molecule in living organisms. The formation of NO has been demonstrated in vivo in various plant tissues exposed to Cd stress, but unfortunately, the time and intensity of NO generation, relatively frequently shows conflicting data. What is more, there is still limited information regarding the functional role of endogenously produced NO in plants challenged with heavy metals. The first pharmacological approaches revealed that exogenously applied NO can alleviate cadmium toxicity in plants, promoting the direct scavenging of reactive oxygen species (ROS) or activating antioxidant enzymes. However, recent reports have indicated that NO even contributes to Cd toxicity by promoting Cd uptake and participates in metal-induced reduction of root growth. In view of this heterogeneous knowledge, much more puzzling if we consider results first obtained using exogenous NO sources, this review is focused mainly on the implication of endogenous NO in plant response to Cd exposure. Furthermore, a basic draft for NO mode of action during cadmium stress is proposed.