Role of the antioxidant system in the regulation of the chlorophyll biosynthesis pathway in the vascular plant Cucumis sativus

2018 ◽  
Vol 45 (4) ◽  
pp. 464
Author(s):  
Aarti Dhepe ◽  
Komal Joshi
Keyword(s):  
Cucumis Sativus ◽  
Antioxidant System ◽  
Chlorophyll Biosynthesis ◽  
Vascular Plant ◽  
Protoporphyrin Ix ◽  
Thioredoxin Reductase ◽  
Ros Generation ◽  
Biosynthesis Pathway ◽  
Cucumis Sativus L

In this study, the role of the antioxidant system has been examined in the regulation of the chlorophyll biosynthesis pathway in the vascular plant Cucumis sativus L. To generate reactive oxygen species (ROS), etiolated (E) and green (G) cucumber cotyledons were treated with methyl viologen (MV) or were exposed to high light (HL, 400–500 µE m–2 s–1). ROS generation was confirmed by measuring proline and H2O2 concentrations. With the effects of the MV- and HL-induced oxidative stress, it was observed that the chlorophyll biosynthesis pathway was severely affected in the HL-treated etiolated cotyledons (E-HL), MV-treated etiolated cotyledons (E-MV) and in MV-treated green cotyledons (G-MV) at 5-amino levulinic acid (ALA) as well as at protoporphyrin IX and Mg-protoporphyrin IX monomethyl ester levels. The antioxidant assays conducted showed that the ascorbate peroxidase (APX) activity had decreased in the E-HL, E-MV and G-MV cotyledons along with the levels of ascorbate and lutein. A decrease in the NADPH-dependent thioredoxin reductase (NTRC) was also observed in the MV-treated cotyledons with a significant impairment of the catalase activity in the E-HL cotyledons. Conversely, in the HL-treated green i.e. G-HL cotyledons, where the accumulation of H2O2 and the inhibition of chlorophyll biosynthesis were not observed, an increase in the levels of APX, NTRC, peroxiredoxin, ascorbate, glutathione and lutein was noted. Thus, the results obtained suggested that the antioxidant system could influence the flow of the chlorophyll biosynthesis pathway through maintaining the levels of H2O2.

scholarly journals The essential role of the transporter ABCG2 in the pathophysiology of erythropoietic protoporphyria

2019 ◽  
Vol 5 (9) ◽  
pp. eaaw6127 ◽  
Author(s):  
Pengcheng Wang ◽  
Madhav Sachar ◽  
Jie Lu ◽  
Amina I. Shehu ◽  
Junjie Zhu ◽  
...  
Keyword(s):  
Essential Role ◽  
Protoporphyrin Ix ◽  
Heme Biosynthesis ◽  
Biosynthesis Pathway ◽  
Efflux Transporter ◽  
Inherited Disease ◽  
Loss Of Function ◽  
Erythropoietic Protoporphyria

Erythropoietic protoporphyria (EPP) is an inherited disease caused by loss-of-function mutations of ferrochelatase, an enzyme in the heme biosynthesis pathway that converts protoporphyrin IX (PPIX) into heme. PPIX accumulation in patients with EPP leads to phototoxicity and hepatotoxicity, and there is no cure. Here, we demonstrated that the PPIX efflux transporter ABCG2 (also called BCRP) determines EPP-associated phototoxicity and hepatotoxicity. We found that ABCG2 deficiency decreases PPIX distribution to the skin and therefore prevents EPP-associated phototoxicity. We also found that ABCG2 deficiency protects against EPP-associated hepatotoxicity by modulating PPIX distribution, metabolism, and excretion. In summary, our work has uncovered an essential role of ABCG2 in the pathophysiology of EPP, which suggests the potential for novel strategies in the development of therapy for EPP.

scholarly journals Role of insect visits on cucumber (Cucumis sativus L.) yield

2018 ◽  
Vol 4 (2) ◽  
pp. 81-88
Author(s):  
MS Hossain ◽  
F Yeasmin ◽  
MM Rahman ◽  
S Akhtar ◽  
MA Hasnat
Keyword(s):  
Cucumis Sativus ◽  
Honey Bee ◽  
Foraging Behaviour ◽  
Apis Cerana ◽  
Bee Pollination ◽  
Cucumis Sativus L ◽  
M 10 ◽  
Hand Pollination ◽  
Insect Visitors

The foraging activities of insect visitors on cucumber (Cucumis sativus L.) were studied. The insect visitors in decreasing order of abundance were: Formica sp.>Apis mellifera>Apis cerana>syrphids≥Apis dorstata. The activity of insects was peaked at 08.00-09.00 am. The foraging behaviour of A. mellifera was also studied. The bees spent significantly more time per flower during morning hours (sec/flower) and foraged significantly fewer flowers (7.9 flowers/min) compared to evening hours. There were significantly more nectar foragers (6.03/m²/10 min) than pollen foragers (5.16/m²/10 min). Most pollen foragers were observed during morning hours (6.59/m²/10 min) whereas nectar foragers were most active during noon hours (6.63/m²/10 min). Highest fruit set was observed in hand pollination (70.68%). Percentage of misshapen fruits was maximum in without honey bee pollination (24.35%). Without honey bee pollination resulted in significantly lowest percentage of healthy fruits (75.25%). Hand pollination ranked highest among the three forms of pollination in respective of fruits (985.13 g), number of seeds per fruit (425.22), fruit diameter (27.1 cm), fruit length (26.7 cm) and weight of 1000-seeds (28.64 g). J. Biodivers. Conserv. Bioresour. Manag. 2018, 4(2): 81-88

Effect of excess manganese on the antioxidant system in Cucumis sativus L. under two light intensities

2006 ◽  
Vol 58 (1-3) ◽  
pp. 197-205 ◽  
Author(s):  
Qinghua Shi ◽  
Zhujun Zhu ◽  
Min Xu ◽  
Qiongqiu Qian ◽  
Jingquan Yu
Keyword(s):  
Cucumis Sativus ◽  
Antioxidant System ◽  
Cucumis Sativus L ◽  
Light Intensities

The role of the cotyledons in the photocontrol of hypocotyl extension in Cucumis sativus L.

Planta ◽  
1974 ◽  
Vol 117 (1) ◽  
pp. 57-66 ◽  
Author(s):  
M. Black ◽  
Janet E. Shuttleworth
Keyword(s):  
Cucumis Sativus ◽  
Cucumis Sativus L

The Role of Polar Movement of IAA in the Development of the Peg in Cucumis sativus L.

1975 ◽  
Vol 136 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Allan Witztum ◽  
Mordechai Gersani
Keyword(s):  
Cucumis Sativus ◽  
Cucumis Sativus L ◽  
Polar Movement

scholarly journals Structure of GUN4 fromChlamydomonas reinhardtii

2015 ◽  
Vol 71 (8) ◽  
pp. 1094-1099 ◽  
Author(s):  
Shabnam Tarahi Tabrizi ◽  
David B. Langley ◽  
Stephen J. Harrop ◽  
Anthony P. Duff ◽  
Robert D. Willows
Keyword(s):  
Crystal Structure ◽  
Chlamydomonas Reinhardtii ◽  
Chlorophyll Biosynthesis ◽  
Conformational Dynamics ◽  
Protoporphyrin Ix ◽  
Biosynthesis Pathway ◽  
Broad Agreement ◽  
Binding Cleft ◽  
Mg Chelatase

The genomes uncoupled 4 (GUN4) protein stimulates chlorophyll biosynthesis by increasing the activity of Mg-chelatase, the enzyme that inserts magnesium into protoporphyrin IX (PPIX) in the chlorophyll biosynthesis pathway. One of the roles of GUN4 is in binding PPIX and Mg-PPIX. In eukaryotes, GUN4 also participates in plastid-to-nucleus signalling, although the mechanism for this is unclear. Here, the first crystal structure of a eukaryotic GUN4, fromChlamydomonas reinhardtii, is presented. The structure is in broad agreement with those of previously solved cyanobacterial structures. Most interestingly, conformational divergence is restricted to several loops which cover the porphyrin-binding cleft. The conformational dynamics suggested by this ensemble of structures lend support to the understanding of how GUN4 binds PPIX or Mg-PPIX.

scholarly journals Functional definition of the tobacco protoporphyrinogen IX oxidase substrate-binding site

2007 ◽  
Vol 402 (3) ◽  
pp. 575-580 ◽  
Author(s):  
Ilka U. Heinemann ◽  
Nina Diekmann ◽  
Ava Masoumi ◽  
Michael Koch ◽  
Albrecht Messerschmidt ◽  
...  
Keyword(s):  
Chlorophyll Biosynthesis ◽  
Substrate Binding ◽  
Protoporphyrin Ix ◽  
Site Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Enzyme Defects ◽  
Km Value ◽  
Function Relationship ◽  
Definition Of

PPO (protoporphyrinogen IX oxidase) catalyses the flavin-dependent six-electron oxidation of protogen (protoporphyrinogen IX) to form proto (protoporphyrin IX), a crucial step in haem and chlorophyll biosynthesis. The apparent Km value for wild-type tobacco PPO2 (mitochondrial PPO) was 1.17 μM, with a Vmax of 4.27 μM·min−1·mg−1 and a catalytic activity kcat of 6.0 s−1. Amino acid residues that appear important for substrate binding in a crystal structure-based model of the substrate docked in the active site were interrogated by site-directed mutagenesis. PPO2 variant F392H did not reveal detectable enzyme activity indicating an important role of Phe392 in substrate ring A stacking. Mutations of Leu356, Leu372 and Arg98 increased kcat values up to 100-fold, indicating that the native residues are not essential for establishing an orientation of the substrate conductive to catalysis. Increased Km values of these PPO2 variants from 2- to 100-fold suggest that these residues are involved in, but not essential to, substrate binding via rings B and C. Moreover, one prominent structural constellation of human PPO causing the disease variegate porphyria (N67W/S374D) was successfully transferred into the tobacco PPO2 background. Therefore tobacco PPO2 represents a useful model system for the understanding of the structure–function relationship underlying detrimental human enzyme defects.

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