scholarly journals Monodehydroascorbate Reductase Plays a Role in the Tolerance of Chlamydomonas reinhardtii to Photooxidative Stress

2019 ◽  
Vol 60 (10) ◽  
pp. 2167-2179 ◽  
Author(s):  
Hui-Ling Yeh ◽  
Tsen-Hung Lin ◽  
Chi-Chih Chen ◽  
Tian-Xing Cheng ◽  
Hsin-Yang Chang ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Enzyme Activity ◽  
Chlamydomonas Reinhardtii ◽  
Light Stress ◽  
Light Condition ◽  
Transcript Level ◽  
Transcript Abundance ◽  
Monodehydroascorbate Reductase ◽  
Photooxidative Stress

Abstract Monodehydroascorbate reductase (MDAR; EC 1.6.5.4) is one of the key enzymes in the conversion of oxidized ascorbate (AsA) back to reduced AsA in plants. This study investigated the role of MDAR in the tolerance of Chlamydomonas reinhardtii P.A. Dangeard to photooxidative stress by overexpression and downregulation of the CrMDAR1 gene. For overexpression of CrMDAR1 driven by a HSP70A:RBCS2 fusion promoter, the cells survived under very high-intensity light stress (VHL, 1,800 μmol�m−2�s−1), while the survival of CC-400 and vector only control (vector without insert) cells decreased for 1.5 h under VHL stress. VHL increased lipid peroxidation of CC-400 but did not alter lipid peroxidation in CrMDAR1 overexpression lines. Additionally, overexpression of CrMDAR1 showed an increase in viability, CrMDAR1 transcript abundance, enzyme activity and the AsA: dehydroascorbate (DHA) ratio. Next, MDAR was downregulated to examine the essential role of MDAR under high light condition (HL, 1,400 μmol�m−2�s−1). The CrMDAR1 knockdown amiRNA line exhibited a low MDAR transcript abundance and enzyme activity and the survival decreased under HL conditions. Additionally, HL illumination decreased CrMDAR1 transcript abundance, enzyme activity and AsA:DHA ratio of CrMDAR1-downregulation amiRNA lines. Methyl viologen (an O2�− generator), H2O2 and NaCl treatment could induce an increase in CrMDAR1 transcript level. It represents reactive oxygen species are one of the factor inducing CrMDAR1 gene expression. In conclusion, MDAR plays a role in the tolerance of Chlamydomonas cells to photooxidative stress.

scholarly journals ND3 and ND4L Subunits of Mitochondrial Complex I, Both Nucleus Encoded in Chlamydomonas reinhardtii, Are Required for Activity and Assembly of the Enzyme

2006 ◽  
Vol 5 (9) ◽  
pp. 1460-1467 ◽  
Author(s):  
Pierre Cardol ◽  
Marie Lapaille ◽  
Pierre Minet ◽  
Fabrice Franck ◽  
René F. Matagne ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Chlamydomonas Reinhardtii ◽  
Complex I ◽  
Nuclear Genome ◽  
Mitochondrial Respiratory Chain ◽  
Nadh:Ubiquinone Oxidoreductase ◽  
Unicellular Green Alga ◽  
Membrane Bound ◽  
Highly Hydrophobic

ABSTRACT Made of more than 40 subunits, the rotenone-sensitive NADH:ubiquinone oxidoreductase (complex I) is the most intricate membrane-bound enzyme of the mitochondrial respiratory chain. In vascular plants, fungi, and animals, at least seven complex I subunits (ND1, -2, -3, -4, -4L, -5, and -6; ND is NADH dehydrogenase) are coded by mitochondrial genes. The role of these highly hydrophobic subunits in the enzyme activity and assembly is still poorly understood. In the unicellular green alga Chlamydomonas reinhardtii, the ND3 and ND4L subunits are encoded in the nuclear genome, and we show here that the corresponding genes, called NUO3 and NUO11, respectively, display features that facilitate their expression and allow the proper import of the corresponding proteins into mitochondria. In particular, both polypeptides show lower hydrophobicity compared to their mitochondrion-encoded counterparts. The expression of the NUO3 and NUO11 genes has been suppressed by RNA interference. We demonstrate that the absence of ND3 or ND4L polypeptides prevents the assembly of the 950-kDa whole complex I and suppresses the enzyme activity. The putative role of hydrophobic ND subunits is discussed in relation to the structure of the complex I enzyme. A model for the assembly pathway of the Chlamydomonas enzyme is proposed.

scholarly journals Photoprotective Role of Photosynthetic and Non-Photosynthetic Pigments in Phillyrea latifolia: Is Their “Antioxidant” Function Prominent in Leaves Exposed to Severe Summer Drought?

2021 ◽  
Vol 22 (15) ◽  
pp. 8303
Author(s):  
Antonella Gori ◽  
Cecilia Brunetti ◽  
Luana Beatriz dos Santos Nascimento ◽  
Giovanni Marino ◽  
Lucia Guidi ◽  
...  
Keyword(s):  
Photosynthetic Pigments ◽  
Light Stress ◽  
Climatic Conditions ◽  
Photochemical Quenching ◽  
Severe Drought ◽  
Summer Drought ◽  
Photooxidative Stress ◽  
Phillyrea Latifolia ◽  
Antioxidant Function

Carotenoids and phenylpropanoids play a dual role of limiting and countering photooxidative stress. We hypothesize that their “antioxidant” function is prominent in plants exposed to summer drought, when climatic conditions exacerbate the light stress. To test this, we conducted a field study on Phillyrea latifolia, a Mediterranean evergreen shrub, carrying out daily physiological and biochemical analyses in spring and summer. We also investigated the functional role of the major phenylpropanoids in different leaf tissues. Summer leaves underwent the most severe drought stress concomitantly with a reduction in radiation use efficiency upon being exposed to intense photooxidative stress, particularly during the central hours of the day. In parallel, a significant daily variation in both carotenoids and phenylpropanoids was observed. Our data suggest that the morning-to-midday increase in zeaxanthin derived from the hydroxylation of ß-carotene to sustain non-photochemical quenching and limit lipid peroxidation in thylakoid membranes. We observed substantial spring-to-summer and morning-to-midday increases in quercetin and luteolin derivatives, mostly in the leaf mesophyll. These findings highlight their importance as antioxidants, countering the drought-induced photooxidative stress. We concluded that seasonal and daily changes in photosynthetic and non-photosynthetic pigments may allow P. latifolia leaves to avoid irreversible photodamage and to cope successfully with the Mediterranean harsh climate.

scholarly journals Understanding the Role of Gibberellic Acid and Paclobutrazol in Terminal Heat Stress Tolerance in Wheat

2021 ◽  
Vol 12 ◽  
Author(s):  
Shivani Nagar ◽  
V. P. Singh ◽  
Ajay Arora ◽  
Rajkumar Dhakar ◽  
Neera Singh ◽  
...  
Keyword(s):  
Gene Expression ◽  
Lipid Peroxidation ◽  
Enzyme Activity ◽  
Abiotic Stress ◽  
Gibberellic Acid ◽  
Stress Tolerance ◽  
Antioxidant Enzyme ◽  
Abiotic Stress Tolerance ◽  
Antioxidant Enzyme Activity

Understanding the physiological mechanism of tolerance under stress conditions is an imperative aspect of the crop improvement programme. The role of plant hormones is well-established in abiotic stress tolerance. However, the information on the role of gibberellic acid (GA) in abiotic stress tolerance in late sown wheat is still not thoroughly explored. Thus, we aimed to investigate the role of endogenous GA3 level in stress tolerance in contrasting wheat cultivars, viz., temperature-tolerant (HD 2643 and DBW 14) and susceptible (HD 2189 and HD 2833) cultivars under timely and late sown conditions. We created the variation in endogenous GA3 level by exogenous spray of GA3 and its biosynthesis inhibitor paclobutrazol (PBZ). Tolerant genotypes had higher antioxidant enzyme activity, membrane stability, and photosynthesis rate, lower lipid peroxidase activity, and better growth and yield traits under late sown conditions attributed to H2O2 content. Application of PBZ escalated antioxidant enzymes activity and photosynthesis rate, and reduced the lipid peroxidation and ion leakage in stress, leading to improved thermotolerance. GA3 had a non-significant effect on antioxidant enzyme activity, lipid peroxidation, and membrane stability. However, GA3 application increased the test weight in HD 2643 and HD 2833 under timely and late sown conditions. GA3 upregulated GA biosynthesis and degradation pathway genes, and PBZ downregulated kaurene oxidase and GA2ox gene expression. GA3 also upregulated the expression of the cell expansins gene under both timely and late sown conditions. Exogenous GA3 did not increase thermotolerance but positively affected test weight and cell expansins gene expression. No direct relationship existed between endogenous GA3 content and stress tolerance traits, indicating that PBZ could have conferred thermotolerance through an alternative mechanism instead of inhibiting GA3biosynthesis.

Role of dyslipidaemia and lipid peroxidation in pregnancy induced hypertension

2015 ◽  
Vol 4 (3) ◽  
pp. 205 ◽  
Author(s):  
Shikha Saxena ◽  
KV Thimmaraju ◽  
PremC Srivastava ◽  
AyazK Mallick ◽  
Biswajit Das ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Pregnancy Induced Hypertension ◽  
Induced Hypertension ◽  
In Pregnancy

Glioblastoma invasion and NMDA receptors: A novel prospect

2019 ◽  
Vol 106 (3) ◽  
pp. 250-260 ◽  
Author(s):  
DN Nandakumar ◽  
P Ramaswamy ◽  
C Prasad ◽  
D Srinivas ◽  
K Goswami
Keyword(s):  
Glutamate Receptors ◽  
Cell Lines ◽  
Intracellular Signaling ◽  
Transcript Level ◽  
Glioblastoma Cells ◽  
Invasion And Migration ◽  
Matrigel Invasion ◽  
Nmdar Activation ◽  
And Migration

Purpose Glioblastoma cells create glutamate-rich tumor microenvironment, which initiates activation of ion channels and modulates downstream intracellular signaling. N-methyl-D-aspartate receptors (NMDARs; a type of glutamate receptors) have a high affinity for glutamate. The role of NMDAR activation on invasion of glioblastoma cells and the crosstalk with α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) is yet to be explored. Main methods LN18, U251MG, and patient-derived glioblastoma cells were stimulated with NMDA to activate NMDAR glutamate receptors. The role of NMDAR activation on invasion and migration and its crosstalk with AMPAR were evaluated. Invasion and migration of glioblastoma cells were investigated by in vitro trans-well Matrigel invasion and trans-well migration assays, respectively. Expression of NMDARs and AMPARs at transcript level was evaluated by quantitative real-time polymerase chain reaction. Results We determined that NMDA stimulation leads to enhanced invasion in LN18, U251MG, and patient-derived glioblastoma cells, whereas inhibition of NMDAR using MK-801, a non-competitive antagonist of the NMDAR, significantly decreased the invasive capacity. Concordant with these findings, migration was significantly augmented by NMDAR in both cell lines. Furthermore, NMDA stimulation upregulated the expression of GluN2 and GluA1 subunits at the transcript level. Conclusions This study demonstrated the previously unexplored role of NMDAR in invasion of glioblastoma cells. Furthermore, the expression of the GluN2 subunit of NMDAR and the differential overexpression of the GluA1 subunit of AMPAR in both cell lines provide a plausible rationale of crosstalk between these calcium-permeable subunits in the glutamate-rich microenvironment of glioblastoma.

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