جستجوی مقالات مرتبط با کلیدواژه "مهارکنندگی" در نشریات گروه "گیاهپزشکی"

Tomato leaf miner Tuta absoluta Meyrick (Lep.: Gelechiidae) is one of the most important pest of tomato around the world which have been introduced to Iran in recent years. Pesticides can usually reduce the damage caused by the pest, however the extensive use of pesticides substantially increase production costs and lead to development of insecticide resistance. Thus, pest resistance and also adverse effects of pesticides on the human health and the environment make search for alternative control method/s inevitable. The aim of this study was to examine the effect of proteinaceous extracts of Datura (Datura stramonium L.), Bean (Phaseolus vulgaris L.), Wild Oat (Avena fatua L.), Broad bean (Vicia faba L.), Amaranth (Amaranthus retroflexus L.), Mung bean (Vigna radiate L.), Pea (Pisum sativum L.), Canola (Brassica napus L.), Triticale (Triticosecale wittmack) and Sivand, Aflak and Alborz wheat (Triticum aestivum L.) cultivars seeds on protease activity of tomato leaf miner. Also in this study optimum pH for protease activity and effects of pH on inhibitory activity of extracts were determined.
For this work fourth instar larvae of Tuta absoluta was used for enzyme extraction. Plant proteinaceous extracts were obtained using 0.1 M NaCl. For protease activity assay 10 μl enzyme extract and 50 μl substrate solution (Azocasein 2%) were mixed with 40 μl of the 20 mM Glycine-NaOH buffer at pH 10.0 After 60 min incubation, 100 μl of 30% trichloroacetic acid (TCA) was added to the reaction mixture, and kept at 4 °C for 30 min, followed by centrifugation at 15,000gfor 15 min to precipitate non-hydrolysis substrate. 100 μl of 1 M NaOH was added to 100μl supernatant and the absorbance at 405 nm was measured. To determine the effect of the seed proteinaceous extracts on the protease activities, enzymes were pre-incubated with each seed extracts for 30 min at 35 °C followed by determination of the residual enzyme activity as described before. To determine the effect of pH on inhibitory activity of the seed extracts, highest concentration of Mung bean, Pea, Canola, Broad bean, wild oat and two wheat cultivars (Alborz and Aflak) seed proteinaceous extracts were incubated along with the enzyme for 30 min at pH set at 6-12, and then enzyme activity was recorded as described before. Protein concentration was measured using bovine serum albumin (Bio-Rad, München, Germany) as a standard.
The effect of pH on protease activity showed that the greatest activity was observed at pH 10 and in the other pHs, it was lower, that this result Corresponded with the pH in other lepidopteran larvae. Also greatest activity of protease at alkaline pH indicates high activity of serine proteases in the alimentary canal. The greatest activity of protease was observed at 40 °C that wasn’t significant compared to 35°C. Effects of all seed proteinaceous extracts on protease activity were concentration dependent, so that the results showed that at the highest concentration, extracts of datura, bean, wild oat, broad bean, amaranth, mung bean, pea, canola, triticale and Sivand, Aflak and Alborz wheat cultivars inhibited the enzyme activity of the larvae with the percentage of 26, 25, 24, 40, 37, 33, 57, 53, 44, 43, 50 and 51, and the lowest concentration of seed extracts inhibited enzyme activity with the percentage of 11, 4, 6, 15, 8, 8, 16, 22, 11, 9, 13 and 16, respectively. Also the greatest inhibition of mung bean, pea, canola, broad bean, wild oat, Alborz and Aflak seed extracts were observed at alkaline pH which is the optimum pH for the activity of this enzyme in the in vitro condition. Due to the alkaline pH of lepidopteran larval gut lumen and maximum activity of protease, which occurs at the alkaline pH, it can be expected that in the in vivo condition, the extracts are impressed protease activity. However, complementary studies will be needed to achieve that.
Our results showed that the proteinaceous seed extracts have biological activity against the tomato leaf miner and therefore it may contribute towards the development of new insect pest control strategies. Thus, further study of these inhibitors including their purification, characterization and structure elucidation as well as the feasibility of their expression in transgenic host plants will unveil more detailed feature of the inhibitor.

The Cabbage butterfly, Pieris brassicae (Lepidoptera: Pieridae), is a cosmopolitan and a destructive cruciferous pest that has been widely distributed. The aim of the current study was to investigate the effect of proteinaceous extracts of mung bean, pea and two wheat cultivars against the Pieris brassicae midgut α-amylase. Results showed that effects of obtained extracts on amylolytic activity of Pieris brassicae was as a dose dependent manner namely with increasing dose, the amylase activity decreased. Also, the results showed highest dose (1/64, 2, 1 and 1 mg.ml-1) of mung bean, cowpea, Alborz, Kavir caused 16, 4, 51, and 55% inhibition of the insect amylase, respectively. Effect of pH on amylase showed that the greatest inhibition of amylase was observed at pH 8 which is the optimum pH for the activity of the enzyme in in-vitro condition. The results revealed that pH had significant effect on inhibition of wheat seed cultivars on this insect α-amylase. It is concluded that extraction obtained from seeds of wheat cultivars affected more α-amylase of the pieris brassica than pea and mung bean seeds. Thus, proteins present in the wheat cultivars have a good potential to be studied further in order to purify them, indentify their structures and investigate their specificity for α-amylase of different animals.