GLUTAMINE SYNTHETASE MUTANT HAVING GLUFOSINATE AMMONIUM RESISTANCE AND APPLICATION THEREOF AND CULTIVATION METHOD THEREFOR

Abstract

Glutamine synthetase mutant having glufosinate ammonium resistance, application thereof and a cultivation method therefor. Comparing with the reference sequence, the amino acid sequence of the glutamine synthetase mutant has one or a combination of the following mutations: (1) the amino acid of the glutamine synthetase mutant corresponding to amino acid site 59 of the reference sequence is mutated to X.sub.1, wherein X.sub.1=A, C, D, E, F, G, H, I, K, P, T, V or Y; (2) the amino acid of the glutamine synthetase mutant corresponding to amino acid site 296 of the reference sequence is mutated to X.sub.2, wherein X.sub.2=A, D, E, G, I, K, M, P, Q, R, S, T, or V.

Claims

1. A glutamine synthetase mutant resistant to glufosinate-ammonium, wherein the glutamine synthetase mutant has one or a combination of two of following mutations when comparing an amino acid sequence of the glutamine synthetase mutant to a reference sequence, wherein (1) the glutamine synthetase mutant has a mutation of X.sub.1 at an amino acid site corresponding to site 59 of the reference sequence, where X.sub.1=A, C, D, E, F, G, H, I, K, P, T, V, or Y; and (2) the glutamine synthetase mutant has a mutation of X.sub.2 at an amino acid site corresponding to site 296 of the reference sequence, where X.sub.2=A, D, E, G, I, K, M, P, Q, R, S, T, or V.

2. The glutamine synthetase mutant resistant to glufosinate-ammonium according to claim 1, wherein the glutamine synthetase mutant is derived from a second plant, wherein the second plant is one selected from the group consisting of rice, soybean, wheat, barley, millet, sunflower, peanut, oat, radish, mung bean, carrot, broad bean, sweet potato, potato, turnip, beet, Chinese cabbage, mustard, cabbage, melon, tomato, eggplant, kidney bean, cowpea, edamame, Chinese chives, pea, green onion, broccoli, kale, onion, leek, spinach, celery, pepper, crowndaisy chrysanthemum, day lily, cotton, lentils, rape, sesame, amaranth, lettuce, cucumber, zucchini, pumpkin, mung bean, bitter gourd, corn, sorghum, unhusked rice, buckwheat, luffa, snake melon, watermelon, alfalfa, herbage, turfgrass, tea, cassava, grape, strawberry, winter melon, tobacco, beet, and sugar cane.

3. The glutamine synthetase mutant resistant to glufosinate-ammonium according to claim 1, wherein the glutamine synthetase mutant has a mutation of S59X.sub.1 at the site corresponding to site 59 of the reference sequence or a mutation of H296X.sub.2 at the site corresponding to site 296 of the reference sequence, and the glutamine synthetase mutant has the same length and the same amino acid residues at remaining sites as SEQ ID NO.1; or the glutamine synthetase mutant has a mutation of S59G at the site corresponding to site 59 of the reference sequence and a mutation of H296R at the site corresponding to site 296 of the reference sequence, and the glutamine synthetase mutant has the same length and the same amino acid residues at remaining sites as any one of SEQ ID NOs. 1-3.

4. An isolated nucleic acid molecule, wherein the isolated nucleic acid molecule encodes the glutamine synthetase mutant resistant to glufosinate-ammonium according to claim 1.

5.-10. (canceled)

11. A method for imparting glufosinate-ammonium resistance to a plant variety, comprising: expressing the glutamine synthetase mutant resistant to glufosinate-ammonium according to claim 1 in a target plant.

12. The method for imparting glufosinate-ammonium resistance to a plant variety according to claim 11, wherein the glutamine synthetase mutant is derived from a second plant, wherein the second plant is one selected from the group consisting of rice, soybean, wheat, barley, millet, sunflower, peanut, oat, radish, mung bean, carrot, broad bean, sweet potato, potato, turnip, beet, Chinese cabbage, mustard, cabbage, melon, tomato, eggplant, kidney bean, cowpea, edamame, Chinese chives, pea, green onion, broccoli, kale, onion, leek, spinach, celery, pepper, crowndaisy chrysanthemum, day lily, cotton, lentils, rape, sesame, amaranth, lettuce, cucumber, zucchini, pumpkin, mung bean, bitter gourd, corn, sorghum, unhusked rice, buckwheat, luffa, snake melon, watermelon, alfalfa, herbage, turfgrass, tea, cassava, grape, strawberry, winter melon, tobacco, beet, and sugar cane.

13. The method for imparting glufosinate-ammonium resistance to a plant variety according to claim 11, wherein the glutamine synthetase mutant has a mutation of S59X.sub.1 at the site corresponding to site 59 of the reference sequence or a mutation of H296X.sub.2 at the site corresponding to site 296 of the reference sequence, and the glutamine synthetase mutant has the same length and the same amino acid residues at remaining sites as SEQ ID NO.1; or the glutamine synthetase mutant has a mutation of S59G at the site corresponding to site 59 of the reference sequence and a mutation of H296R at the site corresponding to site 296 of the reference sequence, and the glutamine synthetase mutant has the same length and the same amino acid residues at remaining sites as any one of SEQ ID NOs. 1-3.

14. The method for imparting glufosinate-ammonium resistance to a plant variety according to claim 11, wherein expressing the glutamine synthetase mutant in the target plant is achieved by any one or a combination of following methods: (a): introducing a nucleic acid molecule encoding the glutamine synthetase mutant into a cell of the target plant, and culturing the cell to make the cell differentiated and developed into a glufosinate-ammonium resistant plant, thereby obtaining the glufosinate-ammonium resistant plant variety; (b): editing an endogenous glutamine synthetase gene of the target plant by gene editing technology to allow the endogenous glutamine synthetase gene to encode the glutamine synthetase mutant, thereby obtaining the glufosinate-ammonium resistant plant variety; (c): mutagenizing a cell or tissue of the target plant or an individual or population of the target plant using mutagenesis technology, and screening out a cell, tissue, or individual encoding the glutamine synthetase mutant in vivo, so as to obtain the glufosinate-ammonium resistant plant variety; and (d): obtaining a plant encoding the glutamine synthetase mutant in vivo through sexual or asexual hybridization, thereby obtaining the glufosinate-ammonium resistant plant variety.

15. The method for imparting glufosinate-ammonium resistance to a plant variety according to claim 11, wherein the target plant is one selected from the group consisting of rice, soybean, wheat, barley, millet, sunflower, peanut, oat, radish, mung bean, carrot, broad bean, sweet potato, potato, turnip, beet, Chinese cabbage, mustard, cabbage, melon, tomato, eggplant, kidney bean, cowpea, edamame, Chinese chives, pea, green onion, broccoli, kale, onion, leek, spinach, celery, pepper, crowndaisy chrysanthemum, day lily, cotton, lentils, rape, sesame, amaranth, lettuce, cucumber, zucchini, pumpkin, mung bean, bitter gourd, corn, sorghum, unhusked rice, buckwheat, luffa, snake melon, watermelon, alfalfa, herbage, turfgrass, tea, cassava, grape, strawberry, winter melon, tobacco, beet, and sugar cane.

16. The glutamine synthetase mutant resistant to glufosinate-ammonium according to claim 1, wherein the reference sequence is an amino acid sequence of a wild-type glutamine synthetase derived from a first plant, and the first plant is rice; and the reference sequence has a base sequence set forth in SEQ ID NO.1.

17. The glutamine synthetase mutant resistant to glufosinate-ammonium according to claim 3, wherein an amino acid sequence of the glutamine synthetase mutant is any one selected from following sequences: (1) a sequence obtained from SEQ ID NO.2 by a mutation of S at site 59 into G and a mutation of H at site 296 into R; and (2) a sequence obtained from SEQ ID NO.3 by a mutation of S at site 59 into G and a mutation of H at site 296 into R.

18. The isolated nucleic acid molecule according to claim 4, wherein a base sequence of the nucleic acid molecule is obtained from any one of SEQ ID NOs. 4-6 by following base mutations: (1) any one of following mutations in SEQ ID NO.4: (a): mutation of AG at sites 175-176 into GC; (b): mutation of A at site 175 into T; (c): mutation of AGC at sites 175-177 into GAT; (d): mutation of AGC at sites 175-177 into GAG; (e): mutation of AG at sites 175-176 into TT; (f): mutation of A at site 175 into G; (g): mutation of AG at sites 175-176 into CA; (h): mutation of G at site 176 into T; (i): mutation of G at site 176 into A; (j): mutation of AG at sites 175-176 into CC; (k): mutation of AG at sites 175-176 into GT; (l): mutation of AG at sites 175-176 into TA; (m): mutation of CA at sites 886-887 into GC; (n): mutation of C at sites 886 and 888 into G; (o): mutation of CA at sites 886-887 into GG; (p): mutation of CA at sites 886-887 into AT; (q): mutation of C at site 886 into A and mutation of C at site 888 into G; (r): mutation of CAC at sites 886-888 into ATG; (s): mutation of C at site 888 into G; (t): mutation of A at site 887 into G; (u): mutation of CAC at sites 886-888 into TCT; (v): mutation of CA at sites 886-887 into AC; (w): mutation of CA at sites 886-887 into GT; and (x): mutation of A at site 175 into G and mutation of A at site 887 into G; (2) mutation of A at site 175 into G and mutation of A at site 887 into G in SEQ ID NO.5; and (3) mutation of A at site 175 into G and mutation of A at site 887 into G in SEQ ID NO.6.

19. The method for imparting glufosinate-ammonium resistance to a plant variety according to claim 13, wherein an amino acid sequence of the glutamine synthetase mutant is any one selected from following sequences: (1) a sequence obtained from SEQ ID NO.2 by a mutation of S at site 59 into G and a mutation of H at site 296 into R; and (2) a sequence obtained from SEQ ID NO.3 by a mutation of S at site 59 into G and a mutation of H at site 296 into R.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0062] In order to explain the technical solutions of the examples of the present disclosure more clearly, the accompanying drawings needed to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain examples of the present disclosure, and therefore should not be regarded as a limitation of the scope. Based on these drawings, those of ordinary skill in the art can obtain other related drawings without inventive work.

[0063] FIG. 1 shows the result of partial alignment of amino acid sequence of rice GS mutants OsA, OsC, OsD, OsE, OsF, OsG, OsH, OsI, OsK, OsP, OsT, OsV, and OsY, and the amino acid sequence of wild-type rice GS OsGS_WT, as provided in Example 1 of the present disclosure.

[0064] FIG. 2 shows the result of partial alignment of amino acid sequences of rice wild-type GS OsGS_WT, rice GS mutant OsGR, wheat wild-type GS TaGS_WT, wheat GS mutant TaGR, soybean wild-type GS GmGS_WT, and soybean GS mutant GmGR, as provided in Example 2 of the present disclosure.

[0065] FIG. 3 shows the result of partial alignment of amino acid sequences of rice wild-type GS OsGS_WT and rice GS mutants OA, OD, OE, OG, OI, OK, OM, OP, OQ, OR, OS, OT, and OV, as provided in Example 3 of the present disclosure.

[0066] FIG. 4 is a schematic structural diagram of a pADV7 vector provided in Experimental Example 1 of the present disclosure.

[0067] FIG. 5 shows the result of the growth of Escherichia coli that are transformed with rice GS mutants OsA, OsC, OsD, OsE, OsF, OsG, OsH, OsI, OsK, OsP, OsT, OsV, and OsY and wild-type rice GS OsGS_WT provided in Example 1 in the media containing different concentrations of glufosinate-ammonium, as provided in Experimental Example 1 of the present disclosure.

[0068] FIG. 6 shows the result of the growth of Escherichia coli that are transformed with rice GS mutant OsGR, wheat GS mutant TaGR, soybean GS mutant GmGR and the controls OsGS_WT, TaGS_WT, GmGS_WT provided in Example 2 in the media containing different concentrations of glufosinate-ammonium, as provided in Experimental Example 2 of the present disclosure.

[0069] FIG. 7 shows the result of the growth of Escherichia coli that are transformed with rice GS mutants OA, OD, OE, OG, OI, OK, OM, OP, OQ, OR, OS, OT, OV and wild-type rice GS OsGS_WT provided in Example 3 in the media containing different concentrations of glufosinate-ammonium, as provided in Experimental Example 3 of the present disclosure.

[0070] FIG. 8 shows the enzymatic kinetic parameters and glufosinate-ammonium resistance parameter IC.sub.50 of rice GS mutants OsC, OsF, OsG, OsP, OR, OsY, OsH, wheat GS mutant TaGR, wild-type rice GS OsGS_WT and wild-type wheat GS TaGS_WT, as provided in Experimental Example 4 of the present disclosure.

[0071] FIG. 9 shows the performance of rice that is transformed with provided rice GS mutant OR and wild-type rice after spraying 1× field dose of glufosinate-ammonium, as provided in Experimental Example 5 of the present disclosure.

[0072] FIG. 10 shows the partial sequence alignment result of rice wild-type GS (SEQ ID NO.1), wheat wild-type GS (SEQ ID NO.2), and soybean wild-type GS (SEQ ID NO.3).

[0073] FIG. 11 is a schematic structural diagram of the pGVP1 vector.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0074] In order to make the objects, technical solutions, and advantages of the examples of the present disclosure clearer, the technical solutions in the examples of the present disclosure will be described clearly and completely below. If specific conditions are not indicated in the examples, it shall be carried out in accordance with the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used without the manufacturer are all conventional products that are commercially available.

[0075] The characteristics and performances of the present disclosure will be further described in detail below in conjunction with examples.

Example 1

[0076] This example provides a plurality of glutamine synthetase (hereinafter referred to as GS) mutants derived from rice (Oryza sativa), and these GS mutants are respectively named: OsA, OsC, OsD, OsE, OsF, OsG, OsH, OsI, OsK, OsP, OsT, OsV, and OsY. These GS mutants, when compared to rice wild-type GS (i.e., the reference sequence, SEQ ID NO.1), have a mutation at a site corresponding to the site 59 of rice wild-type GS, with the specific mutation type as shown in Table 1 and FIG. 1. These GS mutants have the same length and amino acid residues at the remaining sites as those of rice wild-type GS.

TABLE-US-00001 TABLE 1 GS mutants Reference sequence Mutation Type OsA SEQ ID NO. 1 S59A OsC S59C OsD S59D OsE S59E OsF S59F OsG S59G OsH S59H OsI S59I OsK S59K OsP S59P OsT S59T OsV S59V OsY S59Y

Example 2

[0077] This example provides another GS mutant derived from rice, named as OsGR. OsGR, when compared to rice wild-type GS (i.e., the reference sequence, SEQ ID NO.1) has mutations, with the specific mutation type as shown in Table 2 and FIG. 2, at sites corresponding to the sites 59 and 296 of rice wild-type GS. OsGR has the same length and amino acid residue types at the remaining sites as those of rice wild-type GS (SEQ ID NO.1). Namely, the rice wild-type GS (SEQ ID NO.1) is mutated at site 59 thereof into G and at site 296 thereof into R, thereby obtaining OsGR.

[0078] This example also provides a GS mutant derived from wheat (Triticum aestivum), named as TaGR. TaGR, when compared to rice wild-type GS (i.e., the reference sequence, SEQ ID NO.1) has mutations, with the specific mutation type as shown in Table 2 and FIG. 2, at sites corresponding to the sites 59 and 296 of rice wild-type GS. TaGR has the same length and amino acid residue types at the remaining sites as those of wheat wild-type GS (SEQ ID NO.2). Namely, the wheat wild-type GS (SEQ ID NO.2) is mutated at site 59 thereof into G and at site 296 thereof into R, thereby obtaining TaGR.

[0079] This example also provides a GS mutant derived from soybean (Glycine max), named as GmGR. GmGR, when compared to rice wild-type GS (i.e., the reference sequence, SEQ ID NO.1) has mutations, with the specific mutation type as shown in Table 2 and FIG. 2, at sites corresponding to the sites 59 and 296 of rice wild-type GS. GmGR has the same length and amino acid residue types at the remaining sites as those of soybean wild-type GS (SEQ ID NO.3). Namely, the soybean wild-type GS (SEQ ID NO.3) is mutated at site 59 thereof into G and at site 296 thereof into R, thereby obtaining GmGR.

[0080] The partial sequence alignment result of rice wild-type GS (SEQ ID NO.1), wheat wild-type GS (SEQ ID NO.2), and soybean wild-type GS (SEQ ID NO.3) is shown in FIG. 10. FIG. 10 shows that both sites 59 and 296 of GS derived from two different plants of wheat wild-type GS and soybean wild-type GS correspond to sites 59 and 296 of rice wild-type GS.

[0081] The identity and similarity of the sequences of the rice wild-type GS (SEQ ID NO. 1), wheat wild-type GS (SEQ ID NO. 2) and soybean wild-type GS (SEQ ID NO.3) are as follows:

TABLE-US-00002 SEQ ID NO.1 SEQ ID NO.2 SEQ ID NO.3 Identity Similarity Identity Similarity Identity Similarity SEQ ID 100% 100%  92%  98%  89%  96% NO. 1 SEQ ID  92%  98% 100% 100%  86%  96% NO. 2 SEQ ID  89%  96%  86%  96% 100% 100% NO. 3

[0082] Obviously, it should be noted that the site S of the wild-type GS from different plant sources corresponding to site 59 of the rice wild-type GS may not be its own site 59, and the site S may also be its own site 55, 58, 60, 65 and other sites than site 59. The site S is determined according to the specific wild-type GS. As long as the amino acid residues at sites corresponding to site 59 and/or site 296 of the rice wild-type GS are mutated according to the mutation type in Table 2, the resulting GS mutants belong to the protection scope of the present disclosure.

TABLE-US-00003 TABLE 2 GS mutant Reference sequence Mutation Type OsGR SEQ ID NO. 1 S59G and H296R TaGR S59G and H296R GmGR S59G and H296R

Example 3

[0083] This example provides a plurality of other GS mutants derived from rice, and these GS mutants are named: OA, OD, OE, OG, OI, OK, OM, OP, OQ, OR, OS, OT, and OV. These GS mutants, when compared to rice wild-type GS (i.e., the reference sequence, SEQ ID NO.1) have a mutation, with the specific mutation type as shown in Table 3 and FIG. 3, at a site corresponding to the site 296 of rice wild-type GS. These GS mutants have the same length and amino acid residue types at the remaining sites as those of rice wild-type GS (SEQ ID NO.1).

TABLE-US-00004 TABLE 3 GS mutant Reference sequence Mutation Type OA SEQ ID NO. 1 H296A OD H296D OE H296E OG H296G OI H296I OK H296K OM H296M OP H296P OQ H296Q OR H296R OS H296S OT H296T OV H296V

Example 4

[0084] This example provides nucleic acid molecules encoding the GS mutants in the above Examples 1-3.

[0085] The nucleic acid sequence encoding rice wild-type GS (SEQ ID NO.1) is set forth in SEQ ID NO.4; the nucleic acid sequence encoding wheat wild-type GS (SEQ ID NO.2) is set forth in SEQ ID NO.5; and the nucleic acid sequence encoding soybean wild-type GS (SEQ ID NO. 3) is set forth in SEQ ID NO. 6.

[0086] The sequences of the nucleic acid molecules encoding the GS mutants in Examples 1-3 can be obtained by adaptive mutation of base (see Table 4) at base site corresponding to site 59 or 296 of the nucleic acid sequence encoding wild-type GS derived from the same plant. The resulting mutated nucleic acid sequence encodes the corresponding GS mutant. According to the degeneracy of the codons, those of skill in the art can understand that there may be many situations for the codon at the base site that encodes the mutation site of site 59 or 296. Regardless of the codon, as long as it encodes the amino acids of the aforementioned GS mutant, it belongs to the protection scope of the present disclosure.

[0087] The GS mutants in Examples 1-3 and the nucleic acid molecules encoding the same can be obtained by conventional chemical synthesis.

[0088] In this example, the sequences of the nucleic acid molecules encoding the GS mutants in Examples 1-3 are shown in Table 4 below.

TABLE-US-00005 TABLE 4 Mutation included in the encoding Encoding sequence of the GS mutant when GS Plant sequence of compared to the encoding mutant source wild-type GS sequence of wild-type GS OsA rice SEQ ID mutation of AG at sites 175-176 into NO. 4 GC OsC mutation of A at site 175 into T OsD mutation of AGC at sites 175-177 into GAT OsE mutation of AGC at sites 175-177 into GAG OsF mutation of AG at sites 175-176 into TT OsG mutation of A at site 175 into G OsH mutation of AG at sites 175-176 into CA OsI mutation of G at site 176 into T OsK mutation of G at site 176 into A OsP mutation of AG at sites 175-176 into CC OsT mutation of G at site 176 into T; OsV mutation of AG at sites 175-176 into GT OsY mutation of AG at sites 175-176 into TA OA mutation of CA at sites 886-887 into GC OD mutation of C at site 886 into G and mutation of C at site 888 into T OE mutation of C at sites 886 and 888 into G OG mutation of CA at sites 886-887 into GG OI mutation of CA at sites 886-887 into AT OK mutation of C at site 886 into A and mutation of C at site 888 into G OM mutation of CAC at sites 886-888 into ATG OP mutation of A at site 887 into C OQ mutation of C at site 888 into G OR mutation of A at site 887 into G OS mutation of CAC at sites 886-888 into TCT OT mutation of CA at sites 886-887 into AC OV mutation of CA at sites 886-887 into GT OsGR mutation of A at site 175 into G and mutation of A at site 887 into G TaGR wheat SEQ ID mutation of A at site 175 into G and NO. 5 mutation of A at site 887 into G GmGR soybean SEQ ID mutation of A at site 175 into G and NO. 6 mutation of A at site 887 into G

Experimental Example 1

[0089] The rice GS mutants OsA, OsC, OsD, OsE, OsF, OsG, OsH, OsI, OsK, OsP, OsT, OsV, and OsY provided by Example 1 were tested for their glufosinate-ammonium resistance according to the method as follows.

[0090] According to the sequences of the nucleic acid molecules provided in Example 4, the nucleic acid sequences encoding rice GS mutants OsA, OsC, OsD, OsE, OsF, OsG, OsH, OsI, OsK, OsP, OsT, OsV, and OsY were synthesized using chemical synthesis method. Restriction digestion sites (Pac1 and Sbf1) were introduced at both ends thereof, and after restriction digestion, they were linked under the action of ligase to an expression vector (such as pADV7 vector, whose structure is shown in FIG. 4) that was subjected to the same restriction digestion treatment. Then, glutamine synthetase-deficient Escherichia coli was transformed with the resultant. After verification, positive clones were picked up and inoculated in M9 medium containing different concentrations of glufosinate-ammonium to grow, and the growth status of defective Escherichia coli was observed.

[0091] With wild-type rice GS (its amino acid sequence shown in SEQ ID NO. 1 and its encoding gene shown in SEQ ID NO. 4) as a negative control, the glufosinate-ammonium resistance for the GS mutant OsA (S59A, wherein the amino acid S at site 59 of the rice GS is mutated into A), OsC (S59C), OsD (S59D), OsE (S59E), OsF (S59F), OsG (S59G), OsH (S59H), OsI (S591), OsK (S59K), OsP (S59P), OsT (S59T), OsV (S59V), OsY (S59Y) was detected. The results are shown in FIG. 5.

[0092] According to the results in FIG. 5, it can be seen that:

[0093] in a medium containing 0 mM glufosinate-ammonium, deficient strains transformed with the encoding gene that encodes wild-type rice GS (OsGS_WT) and rice GS mutants OsA, OsC, OsD, OsE, OsF, OsG, OsH, OsI, OsK, OsP, OsT, OsV, and OsY could normally grow, indicating that the GS encoded by OsA, OsC, OsD, OsE, OsF, OsG, OsH, OsI, OsK, OsP, OsT, OsV, and OsY had normal GS enzymatic activity; and

[0094] in a medium containing 10 mM glufosinate-ammonium, E. coli (Escherichia coli) transformed with wild-type rice GS could hardly grow, but the growth of E. coli transformed with rice GS mutants OsA, OsC, OsD, OsE, OsF, OsG, OsH, OsI, OsK, OsP, OsT, OsV, and OsY was significantly superior to that of the negative control, indicating that the single mutants including OsA, OsC, OsD, OsE, OsF, OsG, OsH, OsI, OsK, OsP, OsT, OsV, and OsY had glufosinate-ammonium resistance that is significantly better than that of the wild type; and even in a medium with a higher glufosinate-ammonium concentration (50 mM/100 mM), E. coli transformed with rice GS mutants OsC, OsD, OsF, OsG, OsH, OsI, OsK, OsP, and OsY significantly grew.

[0095] These results indicate that the single mutants including OsA, OsC, OsD, OsE, OsF, OsG, OsH, OsI, OsK, OsP, OsT, OsV, and OsY all had glufosinate-ammonium resistance, and the rice GS mutants OsC, OsD, OsF, OsG, OsH, OsI, OsK, OsP, and OsY were more resistant to glufosinate-ammonium.

Experimental Example 2

[0096] With reference to the detection method of Experimental Example 1, glufosinate-ammonium resistance of the rice GS mutant OsGR (S59G and H296R, the amino acid S at site 59 of rice GS is mutated into G and the amino acid H at site 296 is mutated into R), the wheat GS mutant TaGR (S59G and H296R, the amino acid S at site 59 of wheat GS is mutated into G and the amino acid H at site 296 is mutated into R), the soybean GS mutant GmGR (S59G and H296R, the amino acid S at site 59 of soybean GS is mutated into G and the amino acid H at site 296 is mutated into R) provided in Example 2 was verified. The results are shown in FIG. 6.

[0097] According to the results in FIG. 6, it can be seen that:

[0098] in a medium containing 0 mM glufosinate-ammonium, glutamine synthetase-deficient strains transformed with the encoding gene that encodes wild-type rice GS OsGS_WT, wild-type wheat GS TaGS_WT, wild-type soybean GS GmGS_WT, and rice GS mutant OsGR, wheat GS mutant TaGR, and soybean GS mutant GmGR could normally grow, indicating that the GS encoded by rice GS mutant OsGR, wheat GS mutant TaGR, soybean GS mutant GmGR had normal GS enzymatic activity;

[0099] in media containing 2 mM, 5 mM, 10 mM, and 20 mM glufosinate-ammonium, E. coli transformed with wild-type wheat GS TaGS_WT and wild-type soybean GS GmGS_WT could hardly grow, but E. coli transformed with wheat GS mutant TaGR and soybean GS mutant GmGR significantly grew, indicating that the glufosinate-ammonium resistance of wheat GS mutant TaGR and soybean GS mutant GmGR was significantly superior to that of wild type;

[0100] in media containing 10 mM, 20 mM and 300 mM glufosinate-ammonium, E. coli transformed with wild-type rice GS OsGS_WT could hardly grow, but E. coli transformed with rice GS mutant OsGR grew significantly, indicating that the glufosinate-ammonium resistance of rice GS mutant OsGR was significantly superior to that of wild type; and

[0101] in a medium containing 300 mM glufosinate-ammonium, only E. coli transformed with rice GS mutant OsGR grew significantly.

[0102] These results indicate that rice GS mutant OsGR, wheat GS mutant TaGR, and soybean GS mutant GmGR all had glufosinate-ammonium resistance, among which rice GS mutant OsGR is more resistant to glufosinate-ammonium.

Experimental Example 3

[0103] With reference to Experimental example 1, the glufosinate-ammonium resistance of rice GS mutants OA, OD, OE, OG, OI, OK, OM, OP, OQ, OR, OS, OT, and OV provided in Example 3 was detected according to the following method.

[0104] With wild-type rice GS as a negative control, the glufosinate-ammonium resistance of GS mutants OA (H296A, amino acid H at site 296 of rice GS is mutated into A), OD (H296D), OE (H296E), OG (H296G), 01 (H2961), OK (H296K), OM (H296M), OP (H296P), OQ (H296Q), OR (H296R), OS (H296S), OT (H296T), OV (H296V) was detected. The result was shown in FIG. 7.

[0105] According to the results in FIG. 7, it can be seen that:

[0106] in a medium containing 0 mM glufosinate-ammonium, glutamine synthetase-deficient strains transformed with the encoding gene that encodes wild-type rice GS OsGS_WT and rice GS mutants OA, OD, OE, OG, OI, OK, OM, OP, OQ, OR, OS, OT, and OV could normally grow, indicating that GS encoded by OA, OD, OE, OG, OI, OK, OM, OP, OQ, OR, OS, OT, and OV all had normal GS enzymatic activity; and

[0107] in a medium containing 10 mM glufosinate-ammonium, E. coli transformed with wild-type rice GS could hardly grow, but the growth of E. coli transformed with rice GS mutants OA, OD, OE, OG, OI, OK, OM, OP, OQ, OR, OS, OT, and OV was significantly superior to that of the wild type, indicating that the single mutants including OA, OD, OE, OG, OI, OK, OM, OP, OQ, OR, OS, OT, and OV had glufosinate-ammonium resistance that is significantly superior to that of the wild type; even in a medium containing 20 mM glufosinate-ammonium, E. coli transformed with rice GS mutants OA, OD, OE, OI, OK, OR, OT, and OV significantly grew; and further, in a medium containing 50 mM glufosinate-ammonium, E. coli transformed with rice GS mutants OA and OR still significantly grew.

[0108] These results indicate that the single mutants including OA, OD, OE, OG, OI, OK, OM, OP, OQ, OR, OS, OT, and OV all had glufosinate-ammonium resistance, among which the mutants OA and OR were more resistant to glufosinate-ammonium.

Experimental Example 4

[0109] OsC, OsF, OsG, OsH, OsP, and OsY provided in Example 1, OR provided in Example 3, and rice GS mutant OsGR and wheat GS mutant TaGR provided in Example 2 were detected for their enzymatic kinetic parameter, and enzymatic kinetic parameter in the presence of glufosinate-ammonium, using wild-type rice GS OsGS_WT and wild-type wheat GS TaGS_WT as controls according to the following method.

[0110] Vector Construction:

[0111] The nucleic acid sequences encoding the above mutants were each cloned into a prokaryotic expression vector pET32a, and the clone was verified by sequencing.

[0112] 6His Protein Purification:

[0113] The mutant enzyme protein was purified with 6His by a standard method, and its concentration was determined with a protein concentration assay kit with Bradford method. The protein was stored in a protein storage solution.

[0114] Enzymatic Activity Determination:

[0115] 1. Instrument and reagents: ELIASA (Detielab, HBS-1096A), glufosinate-ammonium, substrate sodium L-glutamate (CAS: 6106-04-3).

[0116] 2. Operation Procedure:

[0117] (1) The composition of a reaction solution for determination of enzymatic activity of glutamine synthetase were as follows: 100 mM Tris-HCl (pH 7.5), 10 mM ATP, 20 mM sodium L-glutamate, 30 mM hydroxylamine, 20 mM MgCl.sub.2. 100 μl of the reaction solution after mixed thoroughly was preheated at 35° C. for 5 min, and 10 μl of mutant protein solution (protein concentration of 200 μg/ml) was added to start the reaction. After reaction at 35° C. for 30 min, 110 μl of color developing solution (55 g/L FeCl.sub.3.6H.sub.2O, 20 g/L trichloroacetic acid, 2.1% concentrated hydrochloric acid) was added to terminate the reaction. The absorbance at 540 nm was measured.

[0118] The results are shown in FIG. 8.

[0119] According to the results in FIG. 8, it can be seen that:

[0120] the Km values of the GS mutants were similar or slightly higher as compared to the wild-type controls OsGS_WT and TaGS_WT, indicating that the GS mutants maintained or slightly reduced the sensitivity to a normal substrate while reducing the sensitivity to glufosinate-ammonium inhibitors. The Vmax of other mutants except for OR was higher than that of the wild-type control, indicating that the enzymatic catalytic abilities of these mutants were improved. The wild-type controls were sensitive to glufosinate-ammonium and had IC.sub.50 of 0.7 and 0.6 mM, respectively, while the IC.sub.50 of the mutants was significantly higher than those of the wild-type controls, the IC.sub.50 of OsH, OsY, OR, and OsGR was much higher than those of the wild-type controls. These data illustrate the mechanism for glufosinate-ammonium resistance of the mutants from the perspective of enzyme kinetics.

Experimental Example 5

[0121] The glufosinate-ammonium resistance resulting from the OR mutants provided in Example 3 in transgenic rice was detected according to the following method.

[0122] The nucleic acid sequence encoding OR was inserted into the pGVP1 vector (see FIG. 11) according to a conventional method to obtain the pGVP1-OR vector.

[0123] The pGVP1-OR vector was transformed into competent cells of EHA105 (Agrobactrium tumefaciens), the monoclonal was picked up for colony PCR detection, and positive strains were obtained; then the positive strains were inoculated into 1 mL YEP medium containing 50 μg.Math.mL.sup.−1 kanamycin and 50 μg .Math.mL.sup.−1 rifampicin for propagation, and stored at −80° C. or used in subsequent experiments.

[0124] Rice Transformation:

[0125] 400 μl of strain including pGVP1-OR vector stored at −80° C. was added into a petri dish containing a solid medium containing YEP+50 μg/mL rifampicin+50 μg/mL kanamycin, and cultured in the dark at 28° C. for 24 hours, then the bacteria were added to an infecting medium, and the bacteria solution was adjusted to OD.sub.600=0.2 as an infecting solution.

[0126] Disinfection and pre-culture: mature rice (Nipponbare) seeds were taken and hulled manually, and the plump seeds without bacterial spots were selected and disinfected according to the following procedure. The seeds were placed in a 50 ml sterile centrifuge tube, 70% alcohol was added therein to sterilize it for 30 seconds, and after removal of alcohol, the seeds were washed once with sterile water; 10-20 ml of 2.6% sodium hypochlorite solution was added, and the seed was soaked therein and disinfected for 20 minutes. The sodium hypochlorite solution was removed, and the seeds were soaked and washed 6-7 times, 3 minutes each time, by sterile water.

[0127] Induction and subculture: the seeds were dried on a sterile filter paper, and mature embryos were placed in an induction medium, 12 per dish; after that, the petri dish was sealed with a sealing film and cultured in the dark at 30° C. for 21-28 days. The callus was transferred to a fresh medium for continuing culture for about 7-14 days, and a spherical callus with a size of 1-2 mm was collected as an infection receptor.

[0128] Infection and Co-Culture:

[0129] The callus was added into a centrifuge tube or culture vessel, and a prepared Agrobacterium suspension was added for infection for 10 minutes during which the centrifuge tube or culture vessel was shaken several times; the bacterial solution was removed, the callus was taken out and placed on a sterile filter paper to remove the bacterial solution on the surface (about 30 minutes); and the callus was place on a sterile filter paper in a petri dish and cultured in the dark at 25° C. for 2-3 days.

[0130] Recovery culture: the co-cultured callus was inoculated in a recovery medium and cultured in the dark at 30° C. for 5-7 days.

[0131] The first round of screening: the callus was transferred to a screening medium 1 (S1) and cultured in the dark at 30° C. for 14 days.

[0132] The second round of screening: then, the callus was transferred to a screening medium 2 (S2) and cultured in the dark at 30° C. for 14 days.

[0133] The first round of differentiation: the resistant callus obtained by screening was transferred to a differentiation medium, irradiated by light at 30° C. for 19 hours, and cultured for about 21 days.

[0134] The second round of differentiation: newborn tender shoots were selected and transferred to a new differentiation medium, and cultured continuously for about 21 days.

[0135] When the newborn seedlings grew to a size of about 2 cm, they are transferred to a rooting medium and cultured under light irradiation (16/8 h) at 30° C. for 3 to 4 weeks. When the roots were induced and the seedlings grew to a size of 7 to 10 cm, they were removed from the medium and washed to remove the medium adhered on the roots. They were transferred to a growing tray, the cultivation was continued for about 10 d, and then they were planted in a greenhouse or a field.

[0136] In the above, the formulation of the medium used is described in Chinese patent application No. 2018110706423, named as plant EPSPS mutant including A138T mutation and encoding gene and use thereof.

[0137] Detection of Transgenic Plants:

[0138] Rice plants transformed with OR mutant gene were detected using the PCR method, forward and reverse detection primers were designed according to pGVP1-OR vector sequence and rice reference gene, the PCR amplification products were assayed by 1.5% agarose gel electrophoresis, and those with bands at 452 bp and 629 bp were transgenic plants.

[0139] This example verified the glufosinate-ammonium resistance of OR mutant in rice transgenic plants. The experimental procedure was as follows.

[0140] The transplanted transgenic rice seedlings were evenly arranged in the same experimental area (to avoid overlapping leaves). The area of occupied regions of the experimental group and the control group was calculated. Based on the area of each region, glufosinate-ammonium was sprayed at a dose of 450 g/ha (0.045 g/m.sup.2) as 1× dose.

[0141] According to the above spraying concentration, the corresponding volume of 30% glufosinate-ammonium, which is commercially available, was taken and then diluted with 20-fold volume of water, and the diluted solution was sprayed evenly on the plants of the experimental group and the control group. After the leaves were dry, the plants were moved into the greenhouse or outdoors for cultivation.

[0142] The results on the 7 day after spraying 1× glufosinate-ammonium are shown in FIG. 9.

[0143] According to the results in FIG. 9, it can be seen that the rice wild-type control stopped growing quickly after spraying 1× glufosinate-ammonium, and died and dried up within 7 days; whereas the transgenic rice seedlings including the OR mutant were not significantly affected by glufosinate-ammonium and continued to grow, indicating that the OR mutant could provide glufosinate-ammonium resistance to rice plants. The foregoing descriptions are only preferred examples of the present disclosure, and are not intended to limit the present disclosure. For those of skill in the art, various modifications and changes can be made to the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

INDUSTRIAL APPLICABILITY

[0144] The present disclosure provides a glutamine synthetase mutant resistant to glufosinate-ammonium and its use and breeding method. The glutamine synthetase mutant is capable of imparting glufosinate-ammonium resistance to plants. Use of the glutamine synthetase mutant in crops allows them to grow and develop normally.