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Author: search.filters.author.Singh, PoojaSubject: search.filters.subject.reactive oxygen species

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    Serine hydroxymethyltransferase6 is involved in growth and resistance against pathogens via ethylene and lignin production in Arabidopsis
    (John Wiley & Sons, 2024) Singh, Pooja; Kumari, Aprajita; Khaladhar, Vemula Chandra; Singh, Namrata; Pathak, Pradeep Kumar; Kumar, Vinod; Kumar, Ritika Jantu; Jain, Priyanka; Thakur, Jitendra K.; Fernie, Alisdair R.; Bauwe, Hermann; Raghavendra, A.S.; Gupta, Kapuganti Jagadis
    Photorespiratory serine hydroxymethyltransferases (SHMTs) are important enzymes of cellular one-carbon metabolism. In this study, we investigated the potential role of SHMT6 in Arabidopsis thaliana. We found that SHMT6 is localized in the nucleus and expressed in different tissues during development. Interestingly SHMT6 is inducible in response to avirulent, virulent Pseudomonas syringae and to Fusarium oxysporum infection. Overexpression of SHMT6 leads to larger flowers, siliques, seeds, roots, and consequently an enhanced overall biomass. This enhanced growth was accompanied by increased stomatal conductance and photosynthetic capacity as well as ATP, protein, and chlorophyll levels. By contrast, a shmt6 knockout mutant displayed reduced growth. When challenged with Pseudomonas syringae pv tomato (Pst) DC3000 expressing AvrRpm1, SHMT6 overexpression lines displayed a clear hypersensitive response which was characterized by enhanced electrolyte leakage and reduced bacterial growth. In response to virulent Pst DC3000, the shmt6 mutant developed severe disease symptoms and becomes very susceptible, whereas SHMT6 overexpression lines showed enhanced resistance with increased expression of defense pathway associated genes. In response to Fusarium oxysporum, overexpression lines showed a reduction in symptoms. Moreover, SHMT6 overexpression lead to enhanced production of ethylene and lignin, which are important components of the defense response. Collectively, our data revealed that SHMT6 plays an important role in development and defense against pathogens.
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    Isolation and measurement of respiration and structural studies of purified mitochondria from heterotrophic plant tissues
    (John Wiley & Sons, 2021) Pandey, Sonika; Kumari, Aprajita; Singh, Pooja; Gupta, Kapuganti Jagadis
    Mitochondria are the power houses of eukaryotic cells. These organelles contain various oxidoreductase complexes. Electron transfer from different reducing equivalents channeled via these complexes drives proton translocation across the inner mitochondrial membrane, leading to ATP generation. Plant mitochondria contain alternative NAD(P)H dehydrogenases, alternative oxidase, and uncoupling protein, and TCA cycle enzymes are located in their matrix. Apart from ATP production, mitochondria are also involved in synthesis of vitamins and cofactors and participate in fatty acid, nucleotide, photorespiratory, and antioxidant metabolism. Recent emerging evidence suggests that mitochondria play a role in redox signaling and generation of reactive oxygen and nitrogen species. For mitochondrial studies, it is essential to isolate physiologically active mitochondria with good structural integrity. In this article, we explain a detailed procedure for isolation of mitochondria from various heterotrophic tissues, such as germinating chickpea seeds, potato tubers, and cauliflower florets. This procedure requires discontinuous Percoll gradient centrifugation and can give a good yield of mitochondria, in the range of 4 to 8 mg per 50 g tissue with active respiratory capacity. After MitoTracker staining, isolated mitochondria can be visualized by using a confocal microscope. The structure of mitochondria can be monitored by scanning electron microscopy.
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    Phytoglobin-NO cycle and AOX pathway play a role in anaerobic germination and growth of deepwater rice
    (John Wiley & Sons, 2021) Kumari, Aprajita; Singh, Pooja; Kaladhar, Vemula Chandra; Manbir; Paul, Debarati; Pathak, Pradeep Kumar; Gupta, Kapuganti Jagadis
    An important and interesting feature of rice is that it can germinate under anoxic conditions. Though several biochemical adaptive mechanisms play an important role in the anaerobic germination of rice but the role of phytoglobin-nitric oxide cycle and alternative oxidase pathway is not known, therefore in this study we investigated the role of these pathways in anaerobic germination. Under anoxic conditions, deepwater rice germinated much higher and rapidly than aerobic condition and the anaerobic germination and growth were much higher in the presence of nitrite. The addition of nitrite stimulated NR activity and NO production. Important components of phytoglobin-NO cycle such as methaemoglobin reductase activity, expression of Phytoglobin1, NIA1 were elevated under anaerobic conditions in the presence of nitrite. The operation of phytoglobin-NO cycle also enhanced anaerobic ATP generation, LDH, ADH activities and in parallel ethylene levels were also enhanced. Interestingly nitrite suppressed the ROS production and lipid peroxidation. The reduction of ROS was accompanied by enhanced expression of mitochondrial alternative oxidase protein and its capacity. Application of AOX inhibitor SHAM inhibited the anoxic growth mediated by nitrite. In addition, nitrite improved the submergence tolerance of seedlings. Our study revealed that nitrite driven phytoglobin-NO cycle and AOX are crucial players in anaerobic germination and growth of deepwater rice.
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    Nitric oxide accelerates germination via the regulation of respiration in chickpea
    (Oxford University Press, 2019) Pandey, Sonika; Kumari, Aprajita; Shree, Manu; Kumar, Vinod; Singh, Pooja; Bharadwaj, Chellapilla; Loake, Gary J.; Parida, Swarup K.; Masakapalli, Shyam Kumar; Gupta, Kapuganti Jagadis
    Seed germination is crucial for the plant life cycle. We investigated the role of nitric oxide (NO) in two chickpea varieties that differ in germination capacity: Kabuli, which has a low rate of germination and germinates slowly, and Desi, which shows improved germination properties. Desi produced more NO than Kabuli and had lower respiratory rates. As a result of the high respiration rates, Kabuli had higher levels of reactive oxygen species (ROS). Treatment with the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP) reduced respiration in Kabuli and decreased ROS levels, resulting in accelerated germination rates. These findings suggest that NO plays a key role in the germination of Kabuli. SNAP increased the levels of transcripts encoding enzymes involved in carbohydrate metabolism and the cell cycle. Moreover, the levels of amino acids and organic acids were increased in Kabuli as a result of SNAP treatment. 1 H-nuclear magnetic resonance analysis revealed that Kabuli has a higher capacity for glucose oxidation than Desi. An observed SNAP-induced increase in 13C incorporation into soluble alanine may result from enhanced oxidation of exogenous [13C]glucose via glycolysis and the pentose phosphate pathway. A homozygous hybrid that originated from a recombinant inbred line population of a cross between Desi and Kabuli germinated faster and had increased NO levels and a reduced accumulation of ROS compared with Kabuli. Taken together, these findings demonstrate the importance of NO in chickpea germination via the control of respiration and ROS accumulation.