Publications of NIPGR Scientists

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

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    Nitrate nutrition influences multiple factors in order to increase energy efficiency under hypoxia in Arabidopsis
    (Oxford University Press, 2019) Wany, Aakanksha; Gupta, Alok Kumar; Kumari, Aprajita; Mishra, Sonal; Singh, Namrata; Pandey, Sonika; Vanvari, Rhythm; Igamberdiev, Abir U.; Fernie, Alisdair R.; Gupta, Kapuganti Jagadis
    BACKGROUND AND AIMS: Nitrogen (N) levels vary between ecosystems, while the form of available N has a substantial impact on growth, development and perception of stress. Plants have the capacity to assimilate N in the form of either nitrate (NO3-) or ammonium (NH4+). Recent studies revealed that NO3- nutrition increases nitric oxide (NO) levels under hypoxia. When oxygen availability changes, plants need to generate energy to protect themselves against hypoxia-induced damage. As the effects of NO3- or NH4+ nutrition on energy production remain unresolved, this study was conducted to investigate the role of N source on group VII transcription factors, fermentative genes, energy metabolism and respiration under normoxic and hypoxic conditions. METHODS : We used Arabidopsis plants grown on Hoagland medium with either NO3- or NH4+ as a source of N and exposed to 0.8 % oxygen environment. In both roots and seedlings, we investigated the phytoglobin-nitric oxide cycle and the pathways of fermentation and respiration; furthermore, NO levels were tested using a combination of techniques including diaminofluorescein fluorescence, the gas phase Griess reagent assay, respiration by using an oxygen sensor and gene expression analysis by real-time quantitative reverse transcription-PCR methods. KEY RESULTS : Under NO3- nutrition, hypoxic stress leads to increases in nitrate reductase activity, NO production, class 1 phytoglobin transcript abundance and metphytoglobin reductase activity. In contrast, none of these processes responded to hypoxia under NH4+ nutrition. Under NO3- nutrition, a decreased total respiratory rate and increased alternative oxidase capacity and expression were observed during hypoxia. Data correlated with decreased reactive oxygen species and lipid peroxidation levels. Moreover, increased fermentation and NAD+ recycling as well as increased ATP production concomitant with the increased expression of transcription factor genes HRE1, HRE2, RAP2.2 and RAP2.12 were observed during hypoxia under NO3- nutrition. CONCLUSIONS: The results of this study collectively indicate that nitrate nutrition influences multiple factors in order to increase energy efficiency under hypoxia.
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    Reactive oxygen species, nitric oxide production and antioxidant gene expression during development of aerenchyma formation in wheat
    (Taylor & Francis Group, 2018) Wany, Aakanksha; Gupta, Kapuganti Jagadis
    In response to hypoxia, plant roots produce very high levels of nitric oxide. Recently, it was demonstrated that NO and ethylene both are essential for development of aerenchyma in wheat roots under hypoxia. Increased NO under hypoxia correlated with induction of NADPH oxidase gene expression, ROS production and lipid peroxidation in cortical cells. Tyrosine nitration was prominent in cells developing aerenchyma suggesting that NO and ROS play a key role in development of aerenchyma. However, the role of antioxidant genes during development of aerenchyma is not known, therefore, we checked gene expression of various antioxidants such as SOD1, AOX1A, APX and MnSOD at different time points after hypoxia treatment and found that expression of these genes elevated in 2 h but downregulated in 24 h where development of aerenchyma is prominent. Further, we found that plants growing under ammonium nutrition displayed delayed aerenchyma development. Taken together, new insights presented in this short communication highlighted additional regulatory role of antioxidants gene expression during aerenchyma development.
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    Nitric oxide is essential for the development of aerenchyma in wheat roots under hypoxic stress
    (John Wiley & Sons, 2017) Wany, Aakanksha; Kumari, Aprajita; Gupta, Kapuganti Jagadis
    In response to flooding/waterlogging, plants develop various anatomical changes including the formation of lysigenous aerenchyma for the delivery of oxygen to roots. Under hypoxia, plants produce high levels of nitric oxide (NO) but the role of this molecule in plant-adaptive response to hypoxia is not known. Here, we investigated whether ethylene-induced aerenchyma requires hypoxia-induced NO. Under hypoxic conditions, wheat roots produced NO apparently via nitrate reductase and scavenging of NO led to a marked reduction in aerenchyma formation. Interestingly, we found that hypoxically induced NO is important for induction of the ethylene biosynthetic genes encoding ACC synthase and ACC oxidase. Hypoxia-induced NO accelerated production of reactive oxygen species, lipid peroxidation, and protein tyrosine nitration. Other events related to cell death such as increased conductivity, increased cellulase activity, DNA fragmentation, and cytoplasmic streaming occurred under hypoxia, and opposing effects were observed by scavenging NO. The NO scavenger cPTIO (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt) and ethylene biosynthetic inhibitor CoCl2 both led to reduced induction of genes involved in signal transduction such as phospholipase C, G protein alpha subunit, calcium-dependent protein kinase family genes CDPK, CDPK2, CDPK 4, Ca-CAMK, inositol 1,4,5-trisphosphate 5-phosphatase 1, and protein kinase suggesting that hypoxically induced NO is essential for the development of aerenchyma.