茉莉酸甲酯诱导烟草幼苗抗炭疽病与PAL活性及细胞壁物质的关系

探讨了茉莉酸甲酯(methyl jasmonate, Me-Ja)诱导烟草幼苗抗炭疽病与苯丙氨酸解氨酶(PAL)活性、木质素和富含羟脯氨酸蛋白(HRGP)含量的关系。 Me-Ja处理烟草幼苗不仅可以提高幼苗抗炭疽病的能力,而且明显提高幼苗的PAL活性、木质素和HRGP含量; 3个不同抗性品种的烟草幼苗的PAL酶活性、木质素和HRGP含量三者与感病程度之间的负相关都达到显著水平,表明PAL、木质素和富含羟脯氨酸蛋白(HRGP)在茉莉酸甲酯诱导抗病中起关键作用。     

UV-B对不同发育时期离体蓝莓主要果实品质及相关酶活性的影响

该研究以幼果期、白果期、转色期的离体‘北陆’蓝莓果实为试材,设置0(CK)、5、10、15min紫外光辐照处理,24h后取样分析蓝莓果实中可溶性糖、总酚、类黄酮和花青苷含量,以及苯丙氨酸裂解酶(PAL)和查尔酮异构酶(CHI)活性的变化,探究UV-B紫外照射处理对不同发育时期蓝莓主要果实品质及相关酶活的影响。结果显示:(1)对于幼果期蓝莓,5min UV-B处理可显著增加果实内可溶性糖含量;10min UV-B处理果实PAL活性增加效果最为显著;15min UV-B处理对果实总酚和花青苷积累的促进作用最大,但显著降低了类黄酮含量和CHI活性。(2)对于白果期蓝莓,5min UV-B处理显著增加了果实类黄酮含量和CHI活性,10min处理使果实可溶性糖和总酚含量较对照分别增加25%和18%;15min处理对果实花青苷含量和PAL活性影响作用最大。(3)对于转色期蓝莓,各处理除果实可溶性糖及类黄酮含量降低外,其余物质含量均显著增加。(4)UV-B处理并未改变果实发育过程中可溶性糖、总酚、类黄酮和花青苷含量及PAL、CHI酶活性的积累规律。(5)蓝莓果内PAL活性与其可溶性糖、总酚和类黄酮的积累呈极显著正相关关系,而CHI活性仅与其可溶性糖呈极显著正相关。研究表明,UV-B辐照处理促进了幼果期和白果期可溶性糖的积累,也能促进不同发育时期蓝莓果实总酚和花青苷及白果期类黄酮的积累,对蓝莓果实主要品质能够产生积极的影响。     

不同基因型梨木质素代谢对石细胞含量和果实口感的影响

以五种基因型梨果实为材料,对石细胞团的大小、分布进行解剖学观察,并测定石细胞、木质素含量和木质素相关合成酶PAL、POD、PPO活性,探讨不同基因型梨果实木质素代谢对石细胞含量及口感的影响.结果表明,不同基因型梨木质素含量高时,石细胞含量也高,石细胞团相对较大,分布较密集,口感差.各基因型的梨木质素、石细胞含量和大小为...     

Azoxystrobin induces lignification-related enzymes and phenolics in rice (Oryza sativa L.) against blast pathogen (Pyricularia grisea)

Abstract

This study was conducted to analyse the induction of lignification-related enzymes and phenolic content in rice to blast disease caused by Pyricularia grisea using azoxystrobin. The severity of rice blast was reduced (70% over control) through treatment by azoxystrobin. This reduction in disease severity was mainly associated with induction of host defense mechanisms by azoxystrobin. Increased production of secondary metabolite – phenolic and lignification – related enzymes, namely, peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) were observed in rice plants treated with azoxystrobin.     

Exogenous caffeic acid inhibits the growth and enhances the lignification of the roots of soybean (Glycine max)

The allelopathic effect of caffeic acid was tested on root growth, phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities, hydrogen peroxide (H₂O₂) accumulation, lignin content and monomeric composition of soybean (Glycine max) roots. We found that exogenously applied caffeic acid inhibited root growth, decreased the PAL activity and H₂O₂ content and increased the soluble and cell wall-bound POD activities. The p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) monomers and total lignin (H + G + S) increased in the caffeic acid-exposed roots. When applied in conjunction with piperonylic acid (PIP, an inhibitor of the cinnamate 4-hydroxylase, C4H), caffeic acid equalized the inhibitory effect of PIP, whereas the application of methylene dioxocinnamic acid (MDCA, an inhibitor of the 4-coumarate:CoA ligase, 4CL) plus caffeic acid decreased lignin production. These results indicate that exogenously applied caffeic acid can be channeled into the phenylpropanoid pathway via the 4CL reaction, resulting in an increase of lignin monomers that solidify the cell wall and inhibit root growth.     

Ammonium-related metabolic changes affect somatic embryogenesis in pumpkin (Cucurbita pepo L.)

Somatic embryogenesis in pumpkin can be induced on auxin-containing medium and also on hormone-free medium containing 1 mM ammonium (NH₄⁺) as the sole source of nitrogen. Growth of NH₄⁺-induced embryogenic tissue was slow and caused considerable acidification of the culture medium. Small spherical cells with dense cytoplasma formed proembryogenic cell clusters that could not develop into late stage embryos. Buffering of NH₄⁺ medium with 25 mM 2-(N-morpholino)-ethane-sulfonic acid enhanced tissue proliferation, but no further differentiation was observed. Later stage embryos developed only after re-supply of nitrogen in form of nitrate or l-glutamine. Effects of nitrogen status and pH of culture media on ammonium assimilation were analyzed by following the activity of glutamine synthetase (GS) in relation to phenylalanine ammonia-lyase (PAL). Increased activity of GS and PAL in NH₄⁺ induced tissue coincided with significantly higher activity of stress-related enzymes superoxide dismutase (SOD) and soluble peroxidase (POD), indicating oxidative stress response of embryogenic tissue to NH₄⁺ as the sole source of nitrogen. In addition, considerable increase was observed in callose accumulation and esterase activity, the early markers of somatic embryogenesis. Activity of stress-related enzymes decreased after the re-supply of nitrate (20 mM) or Gln (10 mM) in combination with NH₄⁺ (1 mM), which subsequently triggered globular embryo development. Together, these results suggest that stress responses, as affected by nitrogen supply, contribute to the regulation of embryogenic competence in pumpkin.     

Longer action means better drug: tuning up protein therapeutics

An increasing number of proteins are currently available on the market as therapeutics and this branch of the pharmaceutical industry will expand substantially during the coming years. As many diseases result from dysfunction of proteins forming multicomponent complexes, protein drugs with their inherent high specificity and affinity seem to be optimal medical agents. On the other hand, proteins are often highly instable and sensitive to degradation, which questions their applicability as effective therapeutics. Therefore, redesign and engineering of proteins is usually a required step in the present day drug development.Several approaches have been applied to optimize the protein properties central to their pharmaceutical use. This review focuses on different strategies that improve two crucial factors influencing protein drug efficiency: protein stability and its in vivo half-life. We provide examples of successful genetic and chemical modifications applied in the design of effective protein therapeutics.