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Author: search.filters.author.Wany, AakankshaSubject: search.filters.subject.Nitric oxide

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    Methods for measuring nitrate reductase, nitrite levels, and nitric oxide from plant tissues
    (Springer Nature Publishing AG, 2020) Wany, Aakanksha; Pathak, Pradeep Kumar; Gupta, Kapuganti Jagadis
    Nitrogen (N) is one of the most important nutrients which exist in both inorganic and organic forms. Plants assimilate inorganic form of N [nitrate (NO3−), nitrite (NO2−) or ammonium (NH4+)] and incorporate into amino acids. The metabolism of N involves a series of events such as sensing, uptake, and assimilation. The initial stage is sensing, triggered by nitrate or ammonium signals initiating signal transduction processes in N metabolism. The assimilation pathway initiates with NO3−/NH4+ transport to roots via specific high and low affinity (HATs and LATs) nitrate transporters or directly via ammonium transporters (AMTs). In cytosol the NO3− is reduced to NO2− by cytosolic nitrate reductase (NR) and the produced NO2− is further reduced to NH4+ by nitrite reductase (NiR) in plastids. NR has capability to reduce NO2− to nitric oxide (NO) under specific conditions such as hypoxia, low pH, and pathogen infection. The produced NO acts as a signal for wide range of processes such as plant growth development and stress. Here, we provide methods to measure NR activity, NO2− levels, and NO production in plant tissues.
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    Measurement of nitrate reductase activity in tomato (Solanum lycopersicum L.) leaves under different conditions
    (Springer Nature Publishing AG, 2020) Bulle, Mallesham; Kishorekumar, Reddy; Pathak, Pradeep K.; Wany, Aakanksha; Gupta, Kapuganti Jagadis
    Nitrogen is one of the crucial macronutrients essential for plant growth, development, and survival under stress conditions. Depending on cellular requirement, plants can absorb nitrogen mainly in multiple forms such as nitrate (NO3−) or ammonium (NH4+) or combination of both via efficient and highly regulated transport systems in roots. In addition, nitrogen-fixing symbiotic bacteria can fix atmospheric nitrogen in to NH4+ via highly regulated complex enzyme system and supply to the roots in nodules of several species of leguminous plants. If NO3− is a primary source, it is transported from roots and then it is rapidly converted to nitrite (NO2−) by nitrate reductase (NR) (EC 1.6.6.1) which is a critical and very important enzyme for this conversion. This key reaction is mediated by transfer of two electrons from NAD(P)H to NO3−. This occurs via the three redox centers comprised of two prosthetic groups (FAD and heme) and a MoCo cofactor. NR activity is greatly influenced by factors such as developmental stage and various stress conditions such as hypoxia, salinity and pathogen infection etc. In addition, light/dark dynamics plays crucial role in modulating NR activity. NR activity can be easily detected by measuring the conversion of NO3− to NO2− under optimized conditions. Here, we describe a detailed protocol for measuring relative NR enzyme activity of tomato crude extracts. This protocol offers an efficient and straightforward procedure to compare the NR activity of various plants under different conditions.
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    Current approaches to measure nitric oxide in plants
    (Oxford University Press, 2019) Vishwakarma, Abhaypratap; Wany, Aakanksha; Pandey, Sonika; Bulle, Mallesham; Kumari, Aprajita; Kishorekumar, Reddy; Igamberdiev, Abir U.; Mur, Luis A.J.; Gupta, Kapuganti Jagadis
    Nitric oxide (NO), is now established as an important signalling molecule in plants where they influence growth, development and responses to stress. Despite of extensive research, the most appropriate methods to measure and localise these signalling radicals are debated and still needs investigation. Many confounding factors such as presence of other reactive intermediates, scavenging enzymes and compartmentation, influence how accurately each can be measured. Further, these signalling radicals have short half-lives ranging from seconds to minutes based on the cellular redox condition. Hence, it is necessary to use the sensitive and specific methods in order to understand the contribution of each signalling molecule to various biological processes. In this review, we will provide current state knowledge on NO measurement in plant samples, via various methods. We will also discuss advantages, limitations and wider applications of each method.
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    Chemiluminescence detection of nitric oxide from roots, leaves, and root mitochondria
    (Springer, 2016) Wany, Aakanksha; Gupta, Alok Kumar; Kumari, Aprajita; Gupta, Shika; Mishra, Sonal; Jaintu, Ritika; Pathak, Pradeep K.; Gupta, Kapuganti Jagadis
    NO is a free radical with short half-life and high reactivity; due to its physiochemical properties it is very difficult to detect the concentrations precisely. Chemiluminescence is one of the robust methods to quantify NO. Detection of NO by this method is based on reaction of nitric oxide with ozone which leads to emission of light and amount of light is proportional to NO. By this method NO can be measured in the range of pico moles to nano moles range. Using direct chemiluminescence method, NO emitted into the gas stream can be detected whereas using indirect chemiluminescence oxidized forms of NO can also be detected. We detected NO using purified nitrate reductase, mitochondria, cell suspensions, and roots; detail measurement method is described here.
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    Localization of nitric oxide in wheat roots by DAF fluorescence
    (Springer, 2016) Wany, Aakanksha; Gupta, Kapuganti Jagadis
    Nitric oxide is a free radical signal molecule. Various methods are available for measurement of NO. Out of all methods, fluorescent probes to localize NO is very widely used method. Diaminofluorescein in diacetate form (DAF-2DA) is most widely probe for NO measurement. This method is based on application of 4,5-diaminofluorescein diacetate (DAF-2DA) which is actively diffused into cells, once taken up by cells cytoplasmic esterases cleave the acetate groups to generate 4,5-diaminofluorescein; DAF-2. The generated DAF-2 can readily react with N2O3, which is an oxidation product of NO to generate the highly fluorescent DAF-2T (triazolofluorescein). There are various advantages and disadvantages associated with this method, but to its advantage in diffusion closely to NO producing sites, it is widely used for localization studies. Here, we describe method to make sections of the roots and localization of NO in roots subjected to hypoxic stress.
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    The functional role of nitric oxide in plant mitochondrial metabolism
    (Elsevier B.V., 2016) Gupta, Alok Kumar; Kumari, Aprajita; Mishra, Sonal; Wany, Aakanksha; Gupta, Kapuganti Jagadis
    In recent years, mitochondrial nitric oxide (NO) production has attracted increasing attention. Mitochondria generate NO using nitrite as a substrate. Cytochrome c oxidase and other components of the electron transport chain also contribute to NO generation. Accumulating evidence indicates that mitochondria are scavengers of NO. Furthermore, several genes encoding mitochondrial proteins, as well as mitochondrial proteins, are regulated by NO. In this chapter, we provided an overview of the mechanisms of NO generation and scavenging in mitochondria and of the NO-dependent regulation of proteins and genes encoding mitochondrial proteins. In addition, the functional roles of NO in mitochondrial metabolism, such as inhibition of aconitase, production of ATP and induction of alternative oxidase are presented.