Publications of NIPGR Scientists

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Author: search.filters.author.Singh, PoojaSubject: search.filters.subject.mitochondria

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    Nitric oxide regulates mitochondrial biogenesis in plants
    (John Wiley & Sons, 2023) Kumari, Aprajita; Kaladhar, Vemula Chandra; Yadav, Nidhi; Singh, Pooja; Reddy, Kishorekumar; Gupta, Kapuganti Jagadis
    The site of nitric oxide (NO) production in mitochondrial cytochrome c oxidase and the role of NO in mitochondrial biogenesis are not known in plants. By imposing osmotic stress and recovery on Arabidopsis seedlings we investigated the site of NO production and its role in mitochondrial biogenesis. Osmotic stress reduced growth and mitochondrial number while increasing NO production. During the recovery phase the mitochondrial number increased and this increase was higher in wild type and the high NO-producing Pgb1 silencing line in comparison to the NO-deficient nitrate reductase double mutant (nia1/nia2). Application of nitrite stimulated NO production and mitochondrial number in the nia1/nia2 mutant. Osmotic stress induced COX6b−3 and COA6-L genes encoding subunits of COX. The mutants cox6b-3 and coa6-l were impaired both in NO production and mitochondrial number during stress to recovery suggesting the involvement of these subunits in nitrite-dependent NO production. Transcripts encoding the mitochondrial protein import machinery showed reduced expression in cox6b-3 and coa6-l mutants. Finally, COX6b-3 and COA6-L interacted with the VQ27 motif-containing protein in the presence of NO. The vq27 mutant was impaired in mitochondrial biogenesis. Our results suggest the involvement of COX derived NO in mitochondrial biogenesis.
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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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    The power of the phytoglobin-NO cycle in the regulation of nodulation and symbiotic nitrogen fixation
    (John Wiley & Sons, Inc., 2020) Singh, Pooja; Kumari, Aprajita; Foyer, Christine H.; Gupta, Kapuganti Jagadis
    Recent years have seen a large increase in our understanding of the multifaceted roles of nitric oxide (NO) in plant biology, particularly in the regulation of symbiotic interactions with soil microorganisms. NO serves key functions in the initiation and maintenance of legume–rhizobium symbiosis. Extensive molecular crosstalk between the host legume and the soil rhizobium results in the initiation of symbiosis and the establishment of a highly specialized organ called the nodule, which provides the conditions required for bacterial nitrogen fixation. Within the nodules, the rhizobium bacteria are housed in bacteroids, in which the oxygen is maintained at very low levels allowing the bacterial nitrogenase to function. This enzyme is oxygen sensitive (half maximal inhibitory concentration (IC50) oxygen for nitrogenase is 2.9 µM; Goldberg et al., 1987). Hence, a key feature of the nodule is the maintenance of a strong oxygen diffusion barrier, in which leghaemoglobin is used to transfer oxygen to the plant mitochondria to sustain respiration.