Oligoglucans as Elicitors of an Enzymatic Antioxidant System in Zucchini Squash (<i>Cucurbita pepo</i> L.) Seedlings at Low Temperature

Abstract

Problem statement: Non-controlled low temperatures affect physiological and biochemical processes leading to Reactive Oxygen Species (ROS) accumulation in plants, which normally are stabilized by the antioxidant system. Superoxide Dismutase (SOD), Ascorbate Peroxidase (APX) and Catalase (CAT) are the most important ROS-detoxification enzymes in stressed plants. Approach: The activity of these enzymes were examined in response to fungal Oligoglucans (OG) in cold-stressed cotyledons of Cucurbita pepo L. Cold stress condition was settled in zucchini cotyledons using relative Ion Leakage (IL) and H 2 O 2 accumulation. Then, OG were obtained from Trichoderma harzianum cellwall by enzymatic and chemical hydrolysis. These elicitors were purified by size-exclusion and anionexchange chromatography and tested in cold-stressed cotyledons. Results: No significant changes on H 2 O 2 content and IL were observed between treated and control cold-stressed cotyledons, during the first 7 days of storage at 5°C. Afterwards H 2 O 2 values increased greatly after cold-stressed. Then, cold stress conditions were established (7 d, 5°C). The APX and CAT activities remained stable, but not SOD activity, which decreased about 42% in control cotyledons. When a chemical OG mixture (CM) was applied to cold-stressed cotyledons, APX and CAT activity levels increased. The SOD activity was only increased by an enzymatic OG mixture (EM). The APX activity level was increased in coldstressed cotyledons using OG size-exclusion chromatography fractions from both CM and EM; however, changes in CAT activity were only possible using EM fractions and no changes were detected in SOD activity. The highest CAT activity levels were triggered using OG anion-exchange chromatography sub-fractions from both CM and EM fractions (120 and 119 % of enzymatic activity, respectively). Conclusion: The oxidative stress can be counteracted by the triggering of APX and CAT activity in cold-stressed zucchini cotyledons mediated by T. harzianum cell-wall OG.

Potential of a fly gut microbiota incorporated gel-based larval diet for rearing Bactrocera dorsalis (Hendel)

“…Oriental fruit flies were obtained from a colony maintained for 60 generations on a liquid artificial larval diet [48] in the laboratory of Insect Biotechnology Division (IBD), Institute of Food and Radiation Biology (IFRB), Atomic Energy Research Establishment (AERE), Savar, Dhaka. Approximately 5000 adult flies were maintained in steel-framed cages (76.2 cm × 66 cm × 76.2 cm, H × L × W) covered with wire nets.…”

Electrically induced changes in amaranth seed enzymatic activity and their effect on bioactive compounds content after germination

“…Enzyme extracts were obtained according to Cerón-García et al (2011). For each sample, 1 mL of the reaction mixture (0.1 M sodium phosphate dibasic pH 7.8, 0.01 M L-Methionine, 0.025 M Triton X-100, 11 lM EDTA, 5.7 lM nitroblue tetrazolium chloride (NBT), 1.3 lM riboflavin) was added to aliquot equal to 50 lg of the enzyme extract and the reaction mixtures were illuminated with 30 W white light lamps (General Electric, Connecticut, USA) for 10 min.…”

“…Enzymatic activity of CAT (Aebi 1984) was determined by following the consumption of H 2 O 2 at 240 nm for 3 min at 30°C. Enzyme extracts were obtained according to Cerón-García et al (2011). CAT activity was calculated as the H 2 O 2 molar extinction coefficient (28 mM/cm), which was expressed in mmol of reduced H 2 O 2 /mg of protein per min.…”

“…The enzymatic activity of APX was determined by monitoring absorbance changes at 290 nm for 3 min at 25°C (Nakano and Asada 1987). Enzyme extracts were obtained according to Cerón-García et al (2011). The APX activity was expressed in mmol of oxidized ascorbate/mg of protein per min and the ascorbate molar extinction coefficient (2.8 mM/cm) was used to calculate this enzymatic activity.…”

Oligoglucan Elicitor Effects During Plant Oxidative Stress

“…Our work team, evaluated the triggering of some important antioxidant enzymes in squash (Cucurbita pepo L.) seedlings at low temperature by the spraying of a novel mixture of fungal glucans isolated from Trichoderma harzianum by chemical and/or enzymatic fungal cell wall hydrolysis (Cerón-García et al, 2011). Two of the most active antioxidant enzymes, catalase and ascorbate peroxidase, were triggered by the exogenous elicitation with fungal oligoglucans in cold-stressed squash seedlings.…”