Human-derived insecticidal gene and insecticidal peptide encoded thereby and application thereof

Abstract

The present invention discloses a human-derived insecticidal gene and insecticidal peptide encoded by the same and application thereof. The nucleotide sequence of the human-derived insecticidal gene is as represented by SEQ ID NO.1. The amino acid sequence of the insecticidal peptide encoded by this gene is as represented by SEQ ID NO.2. The insecticidal peptide may be expressed through prokaryotic system. The primary culture has binding activity to Cnaphalocrocis medinalis midgut peritrophic membrane specific receptor BBMV. It is obtained without animal immunization and has a short production cycle and a small amino acid sequence. It is suitable for in vitro mass production and may lower the safety risks resulting from wide use of existing Bt toxins and even might substitute Bt to biologically control agricultural pests in the future. It has important scientific and practical significance to reducing the use of insecticides.

Claims

1. A polynucleotide comprising SEQ ID NO.1.

2. A prokaryotic vector comprising the polynucleotide of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic of F2 ELISA detection result.

(2) FIG. 2 is a schematic of F2 biological determination result.

(3) FIG. 3 is a schematic showing the death condition of Cnaphalocrocis medinalis third instar larvae after they were fed with paddy leaves soaked with F2, CK+ and CK respectively.

(4) FIG. 4 is a schematic showing the death condition of Plutella xylostella third instar larvae after they were fed with cabbage leaves soaked with F2, CK+ and CK respectively.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) Reagents and medium formulae involved in the embodiment:

(6) (1) 2TY fluid medium:

(7) Add 16 g of tryptone, 10 g of yeast extract and 5 g of NaCl in 900 mL of double distilled water, mix them well, set the volume to 1 L by double distilled water, put the liquid in an autoclave, sterilize it at 121 C. for 20 minutes, cool it and store it at 4 C. for future use.
(2) 2TY-AG fluid medium:
Add ampicillin with final concentration of 100 g/ml and glucose with a mass ratio of 1% to 2TY culture medium.
(3) 2TY-AK fluid medium:
Add ampicillin with final concentration of 100 g/ml and kanamycin with final concentration of 50 g/ml to 2TY culture medium.
(4) 2TY-AKG fluid medium:
Add ampicillin with final concentration of 100 g/ml, kanamycin with final concentration of 50 g/ml and glucose with a mass ratio of 1% to 2TY culture medium.
(5) TYE solid medium:
Add 15.0 g of agarose, 8 g of NaCl, 10 g of tryptone and 5 g of yeast extract in 900 ml of double distilled water, set the volume to 1 L by double distilled water, put the liquid in an autoclave, sterilize it at 121 C. for 20 minutes, cool it and store it at 4 C. for future use.
(6) TYE-AG solid medium:
Add ampicillin with final concentration of 100 g/ml and glucose with a mass ratio of 1% to TYE solid medium.
(7) PBS solution:
Weigh 8.0 g of NaCl, 0.2 g of KCl, 2.9 g of Na.sub.2HPO.sub.4.12H.sub.2O and 0.2 g of KH.sub.2PO.sub.4, add them in distilled water respectively, dissolve them thoroughly and set the volume to 1 L.
(8) PBST solution:
0.05% PBST is prepared by adding Tween-20 with a volume ratio of 0.05% to PBS solution.
0.1% PBST is prepared by adding Tween-20 with a volume ratio of 0.1% to PBS solution.
(9) PEG/NaCl solution:
Weigh 20 g of PEG 8000 and 14.61 g of NaCl, add 80 ml of deionized water, set the volume to 100 ml, put the solution in an autoclave, sterilize it at 121 C. for 20 minutes, cool it and store it at 4 C. for future use.
(10) Citrate buffer solution (CPBS, substrate buffer solution, pH5.5):
Weigh 21 g of C.sub.6H.sub.7O.sub.8 (citric acid) and 71.6 g of Na.sub.2HPO.sub.4.12H.sub.2O, add them to distilled water respectively, dissolve them thoroughly and set the volume to 1 L.
(11) Tetramethyl benaidine (TMB) solution:
Weigh 10 mg of TMB, dissolve it in 1 ml of dimethyl sulfoxide, keep the solution in a dark place and store it at 4 C. for future use.
(12) Substrate chromogenic solution:
Composition of 10 ml formula: 9.875 ml of CPBS, 100 l of TMB solution and 25 l H.sub.2O.sub.2 with volume ratio of 20%.
(13) 3% MPBS solution:
Weigh 3 g of skim milk powder, dissolve it in 80 ml of PBS solution and add PBS solution to set the volume to 100 ml.
HRP-goat anti-rabbit IgG described in the embodiment is diluted with 3% MPBS solution.

(8) Sources of the materials involved in the embodiment:

(9) BBMV, irrelevant Anti-Id single-chain antibody, non--type Anti-Id ScFv, cabbage leaves and Plutella xylostella third instar larvae were provided by the Key Laboratory for Agricultural Product Quality and Safety Control Technology and Standard of the Ministry of Agriculture, Jiangsu Academy of Agricultural Sciences;
Negative serum: The negative serum is collected from 1.5-2.0 kg purebred male New Zealand white rabbit. The collection time is one week prior to immunization;
Anti-Cry2Aa polyclonal antibody: Cry2A protein standard substance (Shanghai Youlong Biotech Co., Ltd.) is used as immunogen. Three 1.5-2.0 kg purebred male New Zealand white rabbits are selected as laboratory animals. The concrete immune procedure is as follows: in the first immunization, 200 micrograms of immunogen per rabbit is mixed with isovolumetric FCA (Freund's complete adjuvant). After the mixture is emulsified into an oil-in-water structure, it is subcutaneously injected at multiple points of the back (about 40 points). Two weeks later, it is enhanced by immunogen at the same dose and isovolumetric FIA (Freund's incomplete adjuvant). After that, it is enhanced once every two weeks. In the last time, immunogen is diluted with isovolumetric normal saline and then directly intravenously injected on ear margin. Eight days later, blood is collected from the heart, serum is prepared, thiomersalate with final concentration of 0.01% is added, and then the serum is purified by the method recorded in Contemporary Immunological Technology and Application (Ba Denian, United Press of Peking Medical University and Peking Union Medical College, 1998. 309-322) to obtain anti-Cry2Aa polyclonal antibody.

(10) Humanized phage antibody library, TG1 bacteria and helper phage KM13 were purchased from British Source BioScience;

(11) HRP-goat-anti-M13-IgG was purchased from Wuhan Boster Biological Technology Co., Ltd.;

(12) Cry2Aa toxin and Cry1Ab toxin were purchased from Shanghai Youlong Biotech Co., Ltd.;

(13) Paddy leaves and Cnaphalocrocis medinalis third instar larvae were provided by Yangzhou Luyuan Bio-Chemical Co., Ltd.

Embodiment 1: Screen Insecticidal Peptide

(14) (1) Add 20 l of humanized phage antibody library bacterium liquid to 200 ml of 2TY-AG fluid medium, cultivate it at constant temperature of 37 C. till OD.sub.600 is 0.4, measure 50 ml of the bacterium liquid, add 110.sup.12 pfu of helper phage KM13 for superinfection, incubate the liquid at 37 C. for 30 minutes, then centrifuge it at 3300 g for 10 minutes, discard the supernate, use 100 ml of 2TY-AKG fluid medium to resuspend the precipitate and cultivate it at 30 C. overnight; centrifuge it at 3300 g for 30 minutes next day, collect the supernate, add 20 ml of PEG/NaCl solution, keep it in ice bath for 1 h, then centrifuge it at 3300 g for 30 minutes and resuspend the precipitate by 4 ml of PBS; centrifuge the resuspension solution at 11600 g for 10 minutes. The supernate is amplified phage antibody library;

(15) (2) Use the amplified phage antibody library obtained in step 1 for four rounds of Panning: The screening method is positive and negative screening. Negative serum is used for negative screening and anti-Cry2Aa polyclonal antibody is used for positive screening. A sequence of first negative screening then positive screening is adopted. Negative serum is coated in the negative cell culture flask. Anti-Cry2Aa polyclonal antibody is coated in the positive cell culture flask. The elution method adopts four rounds of competitive elution:

(16) The first round of screening: Coat 4 mL of 100 g/ml negative serum and 4 mL of 100 g/ml anti-Cry2Aa polyclonal antibody to the bottom of the negative cell culture flask and that of the positive cell culture flask respectively, keep it at 4 C. overnight, wash the negative cell culture flask with PBS for 3 times next day, add 1 ml of amplified phage antibody library obtained in step 1, and 4 ml of 3% MPBS solution, put the flask on a shaking table, slowly shake it at room temperature for 1 h, let it rest for 1 h, wash the positive cell culture flask with PBS, suck the liquid in the negative cell culture flask, which has rested for 1 h, into the positive cell culture flask, put the flask on a shaking table, slowly shake it at room temperature for 1 h, let it rest for 1 h again, discard the liquid in the positive cell culture flask, wash the positive flask with 1 ml of 0.05% PBST for 10 times, add 1 ml of 10 mg/ml trypsin to elute the specifically bound phage antibody for 30 minutes. The eluent is phage antibody obtained in the first round of Panning.

(17) The concentrations of the coated anti-Cry2Aa polyclonal antibody panned in the second, third and fourth rounds and negative serum are still 100 g/ml. All the phage antibodies are the phage antibodies obtained from the previous round of panning. The panning method still adopts the strategy of positive and negative screening adopted in the first round. Different from the first round, in the second round, the positive flask is washed with 0.1% PBST solution for 10 times, 1 ml of 10 mg/ml trypsin is added to carry out competitive elution for 1 h; in the third and fourth rounds, the positive flask is washed with 0.1% PBST solution for 20 times and then 500 l of 100 g/ml Cry2Aa polyclonal antibody is added to substitute trypsin for competitive elution, the time of competitive elution in the third round is 1 h, and the time of competitive elution in the fourth round is 30 minutes.

(18) 10 l of the phage antibody panned in the fourth round is used to infect 1 ml of TG1 bacteria in a logarithmic phase. After it is incubated at 37 C. for 1 h, it is coated on TYE-AG solid medium and cultivated at 37 C. overnight; next day, single colonies are picked randomly, incubated on a 96-well plate containing 100 l/well of 2TY-AG fluid medium and cultivated at 37 C. overnight; next day, 2 l of bacterium liquid is sucked from the well plate, transferred to a new 96-well plate and incubated at 37 C. for 2 h. 25 l of helper phage KM13 with titer of 10.sup.12 is added to every well, incubated at 30 C. for 2 h, centrifuged at 1800 g for 10 minutes, the precipitate is resuspended with 150 l of 2TY-AK fluid medium and then cultivated at 30 C. overnight. Next day, it is centrifuged at 1800 g for 30 minutes. The supernate is collected;

(19) (3) 4 g/ml anti-Cry2Aa polyclonal antibody is measured and added to a 96-well plate, 100 l/well, and stored at 4 C. overnight. Next day, 100 l of the supernate obtained in step 2 is added to every well. 100 l of 2TY-AK fluid medium is added to the negative control. They are kept in 37 C. water bath for 2 h. After the plate is washed with 250 l/well of PBST, 100 l of 1:5000 diluted HRP-goat-anti-M13-IgG is added to each well and incubated at 37 C. for 2 h. 100 l of substrate chromogenic solution is added to each well and takes reaction at room temperature for 10 to 20 minutes till blue appears. Lastly 50 l of 2 mol/L H.sub.2SO.sub.4 is added to each well to quickly terminate the reaction. OD.sub.450 is determined by ELIASA. If OD.sub.450 of the solution/OD.sub.450 of negative control is greater than 2.1, it will be considered positive. The supernate in step 2 corresponding to this solution is the screened supernate containing anti-Cry2Aa toxin idiotype single-chain antibody, i.e.: the supernate of insecticidal peptide.

(20) The nucleotide sequence of the screened insecticidal peptide determined by Sanger sequencing method is SEQ ID NO.1, as shown below:

(21) TABLE-US-00001 ccggccctttggcatgcaatttctatttcaggagacagtcataatgaaatacctattgcc 60 tacggcagccgctggattgttattactcgcggcccagccggccatggccgaggtgcagct 120 gttggagtctgggggaggcttggtacagcctggggggtccctgagactctcctgtgcagc 180 ctctggattcacctttagcagctatgccatgagctgggtccgccaggctccagggaaggg 240 gctggagtgggtctcaagtattgattcttatggtactaatacagattacgcagactccgt 300 gaagggccggttcaccatctccagagacaattccaagaacacgctgtatctgcaaatgaa 360 cagcctgagagccgaggacacggccgtatattactgtgcgaaagcttttaattcttttga 420 ctactggggccagggaaccctggtcaccgtctcgagcggtggaggcggttcaggcggagg 480 tggcagcggcggtggcgggtcgacggacatccagatgacccagtctccatcctccctgtc 540 tgcatctgtaggagacagagtcaccatcacttgccgggcaagtcagagcattagcagcta 600 tttaaattggtatcagcagaaaccagggaaagcccctaagctcctgatctatgctgcatc 660 cgctttgcaaagtggggtcccatcaaggttcagtggcagtggatctgggacagatttcac 720 tctcaccatcagcagtctgcaacctgaagattttgcaacttactactgtcaacagtatag 780 ttctagtccttctacgttcggccaagggaccaaggtggaaatcaaacgggcggccgcaca 840 tcatcatcaccatcacggggccgcagaacaaaaactcatctcagaagaggatctgaatgg 900 ggccgcatagactgttgaaagttgtttagcaaaacctcatacagaaaattcatttactaa 960 cgtctggaaagacgacaaaactttaaatcgttacgctaac 1000

(22) The amino acid sequence of the screened insecticidal peptide determined by Sanger sequencing method is SEQ ID NO.2, as shown below:

(23) TABLE-US-00002 MKYLLPTAAAGLLLLAAQPAMAEVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVR 60 H-CDR2 QAPGKGLEWVSSIDSYGTNTDYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAK 120 H-CDR3----Link---- AFNSFDYWGQGTLVTVSSGGGGSGGGGSGGGGSTDIQMTQSPSSLSASVGDRVTITCRAS 180 L-CDR1L-CDR2 QSISSYLNWYQQKPGKAPKLLIYAASALQSGVPSRFSGSGSGTDFTLTISSLQPEDFATY 240 L-CDR3His-tag YCQQYSSSPSTFGQGTKVEIKRAAAHHHHHHGAAEQKLISEEDLNGAA 288

(24) The applicant names this insecticidal peptide as F2.

Embodiment 2: Prepare Primary Culture of F2

(25) The supernate obtained through screening in Embodiment 1 and containing insecticidal peptide is transferred to 10 ml of 2TY-AG fluid medium at a volume ratio of 1:100 and incubated at 37 C. for 2 h. 100 l of helper phage KM13 with titer of 10.sup.12 is added for rescue, incubated at 30 C. for 2 h and centrifuged at 1800 g for 10 minutes. The supernate is removed. 2TY-AK fluid medium is used to resuspend the precipitated bacteria. It is cultivated while being shaken at 30 C. with 250 rpm overnight. Next day it is centrifuged at 1800 g for 30 minutes. Its supernate is supernate containing F2 primary culture.

Embodiment 3: Subtype Identification of F2

(26) (1) ELISA Detection Experiment of Competitive Inhibition

(27) The experiment adopts 6 experimental groups and corresponding control groups. Solutions are prepared based on Table 1.

(28) TABLE-US-00003 TABLE 1 Preparation of solutions for ELISA detection experiment of competitive inhibition Irrelevant Anti-Id 2 TY fluid Group F2 single-chain antibody medium Experimental group 1 5 l 45 l Control group 1 5 l 45 l Experimental group 2 10 l 40 l Control group 2 10 l 40 l Experimental group 3 20 l 30 l Control group 3 20 l 30 l Experimental group 4 30 l 20 l Control group 4 30 l 20 l Experimental group 5 40 l 10 l Control group 5 40 l 10 l Experimental group 6 50 l Control group 6 50 l

(29) In Table 1, F2 is the supernate obtained in Embodiment 2 and containing F2 primary culture;

(30) Add 50 l of 10 g/ml anti-Cry2Aa polyclonal antibody to the solutions prepared in Table 1 respectively, incubate them at 37 C. for 2 h, add them to a 96-well plate coated with 2 g/ml Cry2Aa toxin respectively (the 96-well plate coated with 2 g/ml Cry2Aa toxin is obtained by adding 2 g/ml Cry2Aa toxin to a 96-well plate on the previous day, 100 l/well and keeping it at 4 C. overnight), react for 2 h; wash the plate with 250 l/well of PBST for 3 times, add 100 l/well of 1:5000 diluted HRP-goat anti-rabbit IgG incubate it at room temperature for 1 h; wash the plate with 250 l/well of PBST for 3 times, add 100 l/well of substrate chromogenic solution, take reaction at room temperature for 10 to 20 minutes till blue appears and in the end add 50 l/well of 2 mol/L H.sub.2SO.sub.4 to quickly terminate the reaction; determine OD.sub.450 by ELIASA.

(31) The experimental results are as shown in FIG. 1. The inhibition ratio increases with the increase of F2 content. The control groups do not have the phenomenon of competitive inhibition, suggesting F2 is -type Anti-Id single-chain antibody and can simulate Cry2Aa toxin to competitively bind with anti-Cry2Aa toxin polyclonal antibody.

(32) (2) Biological Determination Experiment

(33) The experiment has experimental group 1, experimental group 2, experimental group 3, positive control group, negative control group 1, negative control group 2 and negative control group 3; the experimental procedure is as follows: (a) Blocking: Coat 100 l/well of 5 g/ml BBMV in a 96-well plate, keep it at 4 C. overnight, wash the plate with 250 l/well of PBST for 3 times next day, add 200 l of BAS with a mass ratio of 3% respectively, incubate it at room temperature for 2 h, and carry out blocking; (b) Sample addition: Wash the 96-well plate blocked in step 1 with 250 l/well of PBST for 3 times, and add samples to the 96-well plate according to Table 2:

(34) TABLE-US-00004 TABLE 2 Preparation of solutions for biological determination experiment of F2 2 g/ml Non--type 2 TY-AG fluid Group Cry2Aa toxin F2 Anti-Id ScFv medium CPBS Experimental group 1 50 l 10 l 40 l Experimental group 2 50 l 30 l 20 l Experimental group 3 50 l 50 l Positive control group 50 l 50 l Negative control group 1 50 l 10 l 40 l Negative control group 2 50 l 30 l 20 l Negative control group 3 50 l 50 l

(35) In Table 2, F2 is the supernate obtained in Embodiment 2 and containing F2 primary culture; (c) Incubate the 96-well plate added with sample in step b at room temperature for 2 h, wash the plate with 250 l/well of PBST for 3 times, add 100 l/well of 10 g/ml anti-Cry2Aa polyclonal antibody, then wash the plate with 250 l/well of PBST for 3 times, add 100 l/well of 1:5000 diluted HRP-goat anti-rabbit IgG and incubate it at room temperature for 1 h; wash the plate with 250 l/well of PBST for 3 times, add 100 l/well of substrate chromogenic solution per well, take reaction at room temperature for 10 to 20 minutes till blue appears and in the end add 50 l/well of 2 mol/L H.sub.2SO.sub.4 to quickly terminate the reaction, and determine OD.sub.450 by ELIASA.

(36) The experimental result is as shown in FIG. 2. Compared with positive control, insecticidal peptide F2 (Experimental groups 1, 2 and 3) can inhibit the binding between Cry2Aa toxin and its receptor BBMV; non--type negative control does not have the phenomenon of inhibition, which further proves that F2 is type.

Embodiment 4: Verify Insecticidal Activity of Insecticidal Peptide F2

(37) The experiment has experimental groups and control groups:

(38) The experimental groups use the supernate (F2) obtained in Embodiment 2 and containing F2 primary culture;

(39) The positive control groups adopt 0.2 g/L Cry1Ab toxin (CK+);

(40) The negative control groups adopt non- type Anti-Id ScFvs (CK);

(41) Experimental Procedure:

(42) Measure experimental groups, positive control groups and negative control groups each 10 ml, put them in sterilized culture dishes, add 6 paddy leaves and 6 cabbage leaves respectively, soak them for 30 minutes, take them out and dry them in the air; feed Cnaphalocrocis medinalis third instar larvae and Plutella xylostella third instar larvae with dried leaves.

(43) The experimental result is as shown in FIG. 3 and FIG. 4. FIG. 3 shows the death condition of Cnaphalocrocis medinalis third instar larvae respectively fed with paddy leaves, which have been soaked with experimental groups (F2), positive control groups (CK+) and negative control groups (CK). FIG. 4 shows the death condition of Plutella xylostella third instar larvae respectively fed with cabbage leaves, which have been soaked with experimental group (F2), positive control group (CK+) and negative control group (CK). It can be seen that insecticidal peptide F2 in the experimental groups has a good insecticidal effect.