Importance of ROS and antioxidant system during the beneficial interactions of mitochondrial metabolism with photosynthetic carbon assimilation

The present study suggests the importance of reactive oxygen species (ROS) and antioxidant metabolites as biochemical signals during the beneficial interactions of mitochondrial metabolism with photosynthetic carbon assimilation at saturating light and optimal CO2. Changes in steady-state photosynthesis of pea mesophyll protoplasts monitored in the presence of antimycin A [AA, inhibitor of cytochrome oxidase (COX) pathway] and salicylhydroxamic acid [SHAM, inhibitor of alternative oxidase (AOX) pathway] were correlated with total cellular ROS and its scavenging system. Along with superoxide dismutase (SOD) and catalase (CAT), responses of enzymatic components-ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), glutathione reductase (GR) and non-enzymatic redox components of ascorbate-glutathione (Asc-GSH) cycle, which play a significant role in scavenging cellular ROS, were examined in the presence of mitochondrial inhibitors. Both AA and SHAM caused marked reduction in photosynthetic carbon assimilation with concomitant rise in total cellular ROS. Restriction of electron transport through COX or AOX pathway had differential effect on ROS generating (SOD), ROS scavenging (CAT and APX) and antioxidant (Asc and GSH) regenerating (MDAR and GR) enzymes. Further, restriction of mitochondrial electron transport decreased redox ratios of both Asc and GSH. However, while decrease in redox ratio of Asc was more prominent in the presence of SHAM in light compared with dark, decrease in redox ratio of GSH was similar in both dark and light. These results suggest that the maintenance of cellular ROS at optimal levels is a prerequisite to sustain high photosynthetic rates which in turn is regulated by respiratory capacities of COX and AOX pathways

<i style="mso-bidi-font-style:normal"><span style="font-size:11.0pt;font-family:"Times New Roman";mso-fareast-font-family: "Times New Roman";mso-bidi-font-family:Mangal;mso-ansi-language:EN-GB; mso-fareast-language:EN-US;mso-bidi-language:HI" lang="EN-GB">Leucaena leucocephala</span></i><span style="font-size:11.0pt;font-family:"Times New Roman";mso-fareast-font-family: "Times New Roman";mso-bidi-font-family:Mangal;mso-ansi-language:EN-GB; mso-fareast-language:EN-US;mso-bidi-language:HI" lang="EN-GB"> (Lam.) de Wit., “subabul” stem lignin: Isolation, structural characterization and thermal properties</span>

406-413<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">Lignin is the second most abundant renewable biopolymer on earth after cellulose. It is being used in many industrial applications due to its abundance. In the present study, lignin was isolated from the stems of Leucaena leucocephala (Lam.) de Wit., a high biomass yielding plant using acidic dioxane under N2 atmosphere. Structural characterization of isolated dioxane lignin (DL) was performed by analytical techniques: UV, FT-IR, 1H NMR and 13C NMR. Their monolignol content was determined by nitrobenzene oxidation followed by HPLC-MS/MS analysis. The data was compared with commercial alkali lignin (AL). The results showed that DL is of hardwood guaiacyl-syringyl (GS) type, whereas AL is softwood type with more guaiacyl units and trace amounts of p-hydroxyphenyl units (H). Thermogravimetric analysis (TGA) of DL showed two stage thermal degradation profile similar to AL. The DTGmax for DL and AL were found in the second major loss event of second stage of TGA at 424°C and 404<span style="font-size:11.0pt;font-family:Symbol;mso-ascii-font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-hansi-font-family:="" "times="" roman";mso-bidi-font-family:mangal;mso-ansi-language:en-gb;="" mso-fareast-language:en-us;mso-bidi-language:hi;mso-char-type:symbol;="" mso-symbol-font-family:symbol"="" lang="EN-GB">°<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">C, respectively. Differential scanning calorimetry (DSC) study exhibited the glass transition temperatures (Tg) at 132<span style="font-size:11.0pt;font-family:Symbol;mso-ascii-font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-hansi-font-family:="" "times="" roman";mso-bidi-font-family:mangal;mso-ansi-language:en-gb;="" mso-fareast-language:en-us;mso-bidi-language:hi;mso-char-type:symbol;="" mso-symbol-font-family:symbol"="" lang="EN-GB">°<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">C and 122<span style="font-size:11.0pt;font-family:Symbol; mso-ascii-font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-hansi-font-family:"times="" roman";mso-bidi-font-family:mangal;mso-ansi-language:="" en-gb;mso-fareast-language:en-us;mso-bidi-language:hi;mso-char-type:symbol;="" mso-symbol-font-family:symbol"="" lang="EN-GB">°<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">C for DL and AL, respectively. The results from thermal stability studies suggest that dioxane lignin isolated from the "miracle tree" (subabul) can be exploited in various thermoplastic industrial applications.</span

Preparation and characterisation of lignin nanoparticles: evaluation of their potential as antioxidants and UV protectants

<div><p>Lignin, an abundant plant biopolymer, is known to possess antioxidant and UV protectant properties in its native state. Nanoparticles exhibit either improved or different properties corresponding to their bulk materials or parent polymers. In the present study, using nanoprecipitation method, dioxane lignin nanoparticles (DLNP) and alkali lignin nanoparticles (ALNP) are fabricated from two different sources of lignin, i.e., hardwood dioxane lignin (DL) extracted from subabul stems and softwood alkali lignin (AL) which is available as a commercial source. Both DLNP and ALNP were fabricated in spherical shape with mean size of 80–104 nm. Analysis of radical scavenging activity revealed that both DLNP and ALNP possess higher antioxidant activity when compared with their parent polymers DL and AL, respectively. UV protectant potential of DLNP and ALNP was validated by monitoring the survival rates of <i>E</i><i>scherichia coli</i> upon UV-induced mortality. DLNP and ALNP were more efficient than DL and AL in protecting <i>E. coli</i> against UV-irradiation-induced mortality. However, upon irradiation for different time periods, DLNP offered pronounced protection for <i>E. coli</i> against UV when compared with ALNP. Thus, the present study demonstrates that the antioxidant and UV protection properties of DLNP can be exploited further in food, pharmaceutical and cosmetic industries.</p></div

Purification and Partial Characterization of Trypsin-Specific Proteinase Inhibitors from Pigeonpea Wild Relative Cajanus platycarpus L.(Fabaceae) active against Gut Proteases of Lepidopteran pest Helicoverpa armigera

AbstractProteinase inhibitors (PIs) are natural defense proteins of plants found to be active against gut proteases of various insects. A pigeonpea wild relative Cajanus platycarpus was identified as a source of resistance against Helicoverpa armigera, a most devastating pest of several crops including pigeonpea. In the light of earlier studies, trypsin-specific PIs (CpPI 63) were purified from mature dry seeds of C. platycarpus (ICPW-63) and characterized their biochemical properties in contributing to H. armigera resistance. CpPI 63 possessed significant H. armigera gut trypsin-like proteinase inhibitor (HGPI) activity than trypsin inhibitor (TI) activity. Analysis of CpPI 63 using two-dimensional (2-D) electrophoresis and matrix assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry revealed that it contained several isoinhibitors and small oligomers with masses ranging between 6-58 kDa. The gelatin activity staining studies suggest that these isoinhibitors and oligomers possessed strong inhibitory activity against H. armigera gut trypsin-like proteases (HGPs). The N-terminal sequence of the isoinhibitors (pI 6.6 and pI 5.6) of CpPI 63 exhibited 80% homology with several Kunitz trypsin inhibitors (KTIs) as well as miraculin-like proteins (MLPs). Further, modification of lysine residue(s) lead to 80% loss in both TI and HGPI activities of CpPI 63. In contrast, the TI and HGPI activities of CpPI 63 were stable over a wide range of temperature and pH conditions. The reported results provide a biochemical basis for pod borer resistance in C. platycarpus

Attenuation of hydrogen peroxide-mediated oxidative stress by Brassica juncea annexin-3 counteracts thiol-specific antioxidant (TSA1) deficiency in Saccharomyces cerevisiae

Dalal A, Vishwakarma A, Singh NK, et al. Attenuation of hydrogen peroxide-mediated oxidative stress by Brassica juncea annexin-3 counteracts thiol-specific antioxidant (TSA1) deficiency in Saccharomyces cerevisiae. FEBS Letters. 2014;588(4):584-593.Brassica juncea annexin-3 (BjAnn3) was functionally characterized for its ability to modulate H(2)O(2-)mediated oxidative stress in Saccharomyces cerevisiae. BjAnn3 showed a significant protective role in cellular-defense against oxidative stress and partially alleviated inhibition of mitochondrial respiration in presence of exogenously applied H2O2. Heterologous expression of BjAnn3 protected membranes from oxidative stress-mediated damage and positively regulated antioxidant gene expression for ROS detoxification. We conclude that, BjAnn3 partially counteracts the effects of thioredoxin peroxidase 1 (TSA1) deficiency and aids in cellular-protection across kingdoms. Despite partial compensation of TSA1 by BjAnn3 in cell-viability tests, the over-complementation in ROS-related features suggests the existence of both redundant (e. g. ROS detoxification) and distinct features (e. g. membrane protection versus proximity-based redox regulator) of both proteins. (C) 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved