NO synthase? Generation of nitric oxide in plants

It has now become well accepted that nitric oxide (NO) has a key role to play in the signalling that takes place in plant cells. However, the sources of NO in plants has been hard to determine and there is considerable debate as to exactly how NO is made by plant cells. In animals nitric oxide synthase (NOS) enzymes have been characterised and such data has been used to inform the studies which have been taking place in plants. However, despite several genomes from higher plants being sequenced, there is no evidence that such species contain NOS sequences. Despite this, a recent search using algal sequences did reveal a NOS-like sequence and such a finding may spark new enthusiasm for the search for a higher plant NOS. However, considerable care needs to be taken in such studies, as the robustness of many of the inhibitors and probes which could be used in such work has been questioned. Here, some of the previous evidence that has been presented for the existence of a plant NOS, along with a discussion of how else plants may produce NO is given

Nitric oxide: Its generation and interactions with other reactive signaling compounds

Nitric oxide (NO) is an immensely important signaling molecule in animals and plants. It is involved in plant reproduction, development, key physiological responses such as stomatal closure, and cell death. One of the controversies of NO metabolism in plants is the identification of enzymatic sources. Although there is little doubt that nitrate reductase (NR) is involved, the identification of a nitric oxide synthase (NOS)-like enzyme remains elusive and it is becoming increasingly clear that such a protein does not exist in higher plants, even though homologues have been found in algae. Downstream from its production, NO can have several potential actions, but none of these will be in isolation from other reactive signaling molecules which have similar chemistry to NO. Therefore, NO metabolism will be taking place in an environment containing reactive oxygen species (ROS), hydrogen sulfide (H2S), glutathione, other antioxidants and within a reducing redox state. Direct reactions with NO are likely to produce new signaling molecules such as peroxynitrite and nitrosothiols, and it is probable that chemical competitions will exist which will determine the ultimate end result of signaling responses. How NO is generated in plants cells and how NO fits into this complex cellular environment needs to be understood

Competition of reactive signals and thiol modifications of proteins

It is clear that cells are constantly bombarded by multiple signals, often initiating similar, or even conflicting, responses. Important players in this suite of signals are the reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), the reactive nitrogen species (RNS), such as nitric oxide (NO) and sulfur-based molecules, such as hydrogen sulfide (H2S). These compounds are often involved in stress responses and dysfunction of these signaling systems is often involved in disease [1-3]. This commentary discusses the interactions of such signals, which was discussed in a previous paper [3]. It was argued that all these molecules are not acting in the same manner, and that H2S was acting in a role which moderated the effects of ROS and NO

Oxygen: Highlights from the papers published in the journal up to February 2024

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Nitric oxide signaling in plants

Nitric oxide (NO) is an integral part of cell signaling mechanisms in animals and plants. In plants, its enzymatic generation is still controversial. Evidence points to nitrate reductase being important, but the presence of a nitric oxide synthase-like enzyme is still contested. Regardless, NO has been shown to mediate many developmental stages in plants, and to be involved in a range of physiological responses, from stress management to stomatal aperture closure. Downstream from its generation are alterations of the actions of many cell signaling components, with post-translational modifications of proteins often being key. Here, a collection of papers embraces the differing aspects of NO metabolism in plants

Distortional Buckling Formulae for Thin Walled Channel and Z-sections with Return Lips

Cold-formed Channel- and Z-sections subject to both flexure and torsion may undergo distortional buckling where the flange and lip rotate about the flange/web junction. This mode of failure is prevalent in purlin sections when lateral deformation of the section is prevented and when the sections are manufactured from high strength steel. In an attempt to prevent distortional buckling, some manufacturers have added additional return lips to the flange lips to produce complex edge stiffeners. The Australian/New Zealand Standard for Cold-Formed Steel Structures includes design rules for determining the distortional buckling strength of cold-formed beam and column sections. These design rules require the computation of the elastic distortional buckling stress. Appendix D of ASINZS 4600 provides design rules for computing the elastic distortional buckling stress of general channels in compression, simple lipped channels in compression and simple lipped Channel- and Z-sections in bending about an axis perpendicular to the web. The paper describes general formulations for computing the elastic distortional buckling stresses of sections with return lips including those with sloping lips and return lips. The accuracy of the formulations is compared with the results for a large range of section geometries using a finite strip buckling analysis which can be regarded as providing accurate solutions for distortional buckling stress. Explicit expressions are presented in the paper for the flange properties

RAZINE LIPIDNE PEROKSIDACIJE U DIJELOVIMA SJEMENA SOJE (Glycine max (L.) Merr.) KAO POSLJEDICA STRESA PRI USVAJANJU VODE

High rainfall and rapid water uptake by dry seed after sowing in the field can result in so-called seed imbibitional damage. Here, lipid peroxidation levels were evaluated in seed testa, embryos and cotyledons of three soybean cultivars (Podravka 95, Tisa and Vita), after 3, 6, 12 and 24 h of seed imbibition in water at 20oC. In general, lipid peroxidation was enhanced in soybean embryos and the lowest vales were observed in seed testa. With respect to imbibition duration, the highest lipid peroxidation was observed after 3 h of imbibition and decreased thereafter in seed of Podravka 95 and Vita, with similar trend regarding seed of the same age.Intenzivne oborine i intenzivno usvajanje vode suhoga sjemena nakon sjetve u polju mogu rezultirati takozvanim imbibicijskim oštećenjem sjemena. U ovom istraživanju analiziran je intenzitet lipidne peroksidacije u sjemenjači, klici i kotiledonima sjemena tri sorte soje (Podravka 95, Tisa i Vita), nakon 3, 6, 12 i 24 imbibicije u vodi pri 20oC. U cjelini, lipidna peroksidacija bila je povećana u klici soje, a najslabije izražena u sjemenjači. S obzirom na dužinu imbibicije, najveći intenzitet lipidne peroksidacije utvrđen je nakon 3 h imbibicije, nakon čega se smanjivao kod sorata Podravka 95 i Vita, uz sličan trend, s obzirom na sjeme iste starosti

Hydrogenases and the role of molecular hydrogen in plants

Molecular hydrogen (H2) has been suggested to be a beneficial treatment for a range of species, from humans to plants. Hydrogenases catalyze the reversible oxidation of H2, and are found in many organisms, including plants. One of the cellular effects of H2 is the selective removal of reactive oxygen species (ROS) and reactive nitrogen species (RNS), specifically hydroxyl radicals and peroxynitrite. Therefore, the function of hydrogenases and the action of H2 needs to be reviewed in the context of the signalling roles of a range of redox active compounds. Enzymes can be controlled by the covalent modification of thiol groups, and although motifs targeted by nitric oxide (NO) can be predicted in hydrogenases sequences it is likely that the metal prosthetic groups are the target of inhibition. Here, a selection of hydrogenases, and the possibility of their control by molecules involved in redox signalling are investigated using a bioinformatics approach. Methods of treating plants with H2 along with the role of H2 in plants is also briefly reviewed. It is clear that studies report significant effects of H2 on plants, improving growth and stress responses, and therefore future work needs to focus on the molecular mechanisms involved

Expression and localization of aquaporin water channels in adult pig urinary bladder

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