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Inhibitory Effects of Plant Trypsin Inhibitors Msti-94 and Msti-16 on Therioaphis trifolii (Monell) (Homoptera: Aphididae) in Alfalfa

1
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
2
College of Plant Protection, Shenyang Agricultural University, Shenyang 110161, China
3
Department of Agriculture, The University of Swabi, Anbar-23561, Swabi, Khyber Pakhtunkhwa, Pakistan
4
AgResearch, Lincoln Research Centre, Christchurch 8140, New Zealand
5
National Animal Husbandry Service, Beijing 100125, China
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this study.
Insects 2019, 10(6), 154; https://doi.org/10.3390/insects10060154
Received: 6 March 2019 / Revised: 22 May 2019 / Accepted: 24 May 2019 / Published: 30 May 2019
The spotted alfalfa aphid (Therioaphis trifolii (Monell)) is a known destructive pest that can significantly reduce alfalfa yields. Two differentially up-regulated alfalfa trypsin inhibitors ‘Msti-94’ and ‘Msti-16’ in transcriptome were verified in terms of their mRNA levels using RT-qPCR. The prokaryotic expression vector was constructed and its biological functions, including phenotypic and physiological responses, were verified through feeding spotted alfalfa aphids with active recombinant protein mixed with an artificial diet. Gene clone and gene prokaryotic expression confirmed that Msti-94 had a size of 651 bp, encoded 216 amino acids with a predicted protein weight of 23.5 kDa, and a pI value of 6.91. Similarly, the size of Msti-16 was 612 bp, encoded 203 amino acids, and had a predicted protein weight of 22.2 kDa with a pI value of 9.06. We concluded that both Msti-94 and Msti-16 acted as a stomach poison with survival rates reduced to 21.7% and 18.3%, respectively, as compared to the control, where the survival rate was significantly (p < 0.05) higher (60.0%). Aphid reproduction rates were significantly reduced, after 72 h of feeding, in both the Msti-94 and Msti-16 treatments compared to the controls. A concentration of 800 μg/mL (0.8 mg/mL) of recombinant protein and 5000 μg/mL (5 mg/mL) of recombinant expressing bacteria that inhibits the total protease, which ultimately disrupted the activity of trypsin, chymotrypsin, and aminopeptidase. View Full-Text
Keywords: enzyme activity; reproduction; spotted alfalfa aphid; survival; trypsin inhibitor enzyme activity; reproduction; spotted alfalfa aphid; survival; trypsin inhibitor
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MDPI and ACS Style

Zhao, H.; Ullah, H.; McNeill, M.R.; Du, G.; Hao, K.; Tu, X.; Zhang, Z. Inhibitory Effects of Plant Trypsin Inhibitors Msti-94 and Msti-16 on Therioaphis trifolii (Monell) (Homoptera: Aphididae) in Alfalfa. Insects 2019, 10, 154.

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