Mutant

1. A Nicotiana benthamiana plant or plant cell comprising transcription activator-like (TAL) effector endonuclease-induced mutations in each of a plurality of XylT1 and XylT2 alleles and in each of a plurality of FucT1 and FucT2 alleles, wherein said TAL effector endonuclease-induced mutations were induced by:

(a) a first TAL effector endonuclease that binds to a first set of nucleic acid sequences selected from the group consisting SEQ ID NOs: 47 and 48, SEQ ID NOs: 49 and 50, and SEQ ID NOs: 51 and 52, each of said first pair of nucleic acid sequences located in the plurality of XylT1 and XylT2 alleles, and

(b) a second TAL effector endonuclease that binds to a second set of nucleic acid sequences selected from the group consisting SEQ ID NOs: 53 and 54, SEQ ID NOs: 55 and 56, SEQ ID NOs: 57 and 58, SEQ ID NOs: 58 and 59, and SEQ ID NOs: 62 and 63, each of said second pair of nucleic acid sequences located in the plurality of FucT1 and FucT2 alleles,

wherein levels of beta-1,2-xylosyl-sugars and core alpha-1,3-fucosyl-sugars on N-glycan structures of glycoproteins produced in said plant or plant cell are reduced as compared to a corresponding plant or plant cell that does not contain said TAL effector endonuclease-induced mutations.

2. The plant or plant cell of claim 1 , wherein said plant or plant cell comprises a nucleic acid encoding a heterologous polypeptide.

3. The plant or plant cell of claim 1 , wherein each of said mutations is a deletion of more than one nucleotide.

4. The plant or plant cell of claim 1 , wherein each of said one or more XylT1 and XylT2 alleles and said one or more FucT1 and FucT2 alleles has a deletion of an endogenous nucleic acid sequence and does not include any exogenous nucleic acid.

5. The plant or plant cell of claim 1 , wherein said first TAL effector endonuclease binds to SEQ ID NOs: 51 and 52, and wherein said second TAL effector endonuclease binds to SEQ ID NOs: 58 and 59.

6. The plant or plant cell of claim 1 , wherein levels of beta-1,2-xylosyl-sugars on N-glycan structures of glycoproteins produced in said plant or plant cell are undetectable.

7. The plant or plant cell of claim 1 , wherein said Nicotiana benthamiana plant cell is a protoplast.

8. A Nicotiana benthamiana plant comprising a mutation in each of a plurality of XylT1 and XylT2 alleles and a mutation in each of a plurality of FucT1 and FucT2 alleles, wherein said plant is produced by a method comprising:

(a) contacting a population of Nicotiana benthamiana plant cells comprising functional XylT1 and XylT2 alleles and functional FucT1 and FucT2 alleles with (i) a first TAL effector endonuclease that binds to a first pair of nucleic acid sequences selected from the group consisting SEQ ID NOs: 47 and 48, SEQ ID NOs: 49 and 50, and SEQ ID NOs: 51 and 52, each of said first pair of nucleic acid sequences located in the plurality of XylT1 and XylT2 alleles, and (ii) a second TAL effector endonuclease that binds to a second pair of nucleic acid sequences selected from the group consisting SEQ ID NOs: 53 and 54, SEQ ID NOs: 55 and 56, SEQ ID NOs: 57 and 58, SEQ ID NOs: 58 and 59, and SEQ ID NOs: 62 and 63, each of said second pair of nucleic acid sequences located in the plurality of FucT1 and FucT2 alleles,

(b) selecting, from said population, a cell in which each of said plurality of XylT1 and XylT2 alleles and each of said plurality of FucT1 and FucT2 alleles have been inactivated, and

(c) regenerating said selected plant cell into the Nicotiana benthamiana plant, wherein said selected Nicotiana benthamiana plant produces reduced levels of beta-1,2-xylosyl-sugars and core alpha-1,3-fucosyl-sugars on N-glycan structures of glycoproteins compared to a corresponding plant that does not contain said mutations.

9. The plant of claim 8 , wherein said plant comprises a nucleic acid encoding a heterologous polypeptide.

10. The plant of claim 8 , wherein each of said mutations is a deletion of more than one nucleotide.

11. The plant of claim 8 , wherein said first TAL effector endonuclease binds to SEQ ID NOs: 51 and 52, and wherein said second TAL effector endonuclease binds to SEQ ID NOs: 58 and 59.

12. A Nicotiana benthamiana plant cell comprising a mutation in each of a plurality of XylT1 and XylT2 alleles and a mutation in each of a plurality of FucT1 and FucT2 alleles, wherein said plant cell is produced by a method comprising:

(a) contacting a population of Nicotiana benthamiana plant cells comprising functional XylT1 and XylT2 alleles and functional FucT1 and FucT2 alleles with (i) a first TAL effector endonuclease that binds to a first pair of nucleic acid sequences selected from the group consisting SEQ ID NOs: 47 and 48, SEQ ID NOs: 49 and 50, and SEQ ID NOs: 51 and 52, each of said first pair of nucleic acid sequences located in the plurality of XylT1 and XylT2 alleles, and (ii) a second TAL effector endonuclease that binds to a second pair of nucleic acid sequences selected from the group consisting SEQ ID NOs: 53 and 54, SEQ ID NOs: 55 and 56, SEQ ID NOs: 57 and 58, SEQ ID NOs: 58 and 59, and SEQ ID NOs: 62 and 63, each of said second pair of nucleic acid sequences located in the plurality of FucT1 and FucT2 alleles,

(b) selecting, from said population, a cell in which each of said plurality of XylT1 and XylT2 alleles and each of said plurality of FucT1 and FucT2 alleles have been inactivated, wherein said selected Nicotiana benthamiana plant cell produces reduced levels of core alpha-1,3-fucosyl-sugars on N-glycan structures of glycoproteins compared to a corresponding plant cell that does not contain said mutations.

13. The plant cell of claim 12 , wherein said plant cell comprises a nucleic acid encoding a heterologous polypeptide.

14. The plant cell of claim 12 , wherein each of said mutations is a deletion of more than one nucleotide.

15. The plant cell of claim 12 , wherein said first TAL effector endonuclease binds to SEQ ID NOS: 51 and 52, and wherein said second TAL effector endonuclease binds to SEQ ID NOS: 58 and 59.

16. A population of plant cells comprising one or more plant cell according to claim 12 .

17. A Nicotiana benthamiana plant or plant cell comprising a modified glycoprotein, said modified glycoprotein comprising reduced levels of beta-1,2-xylosyl-sugars and core alpha-1,3-fucosyl-sugars on N-glycan structures,

said plant or plant cell comprising transcription activator-like (TAL) effector endonuclease-induced mutations in each of a plurality of XylT1 and XylT2 alleles and in each of a plurality of FucT1 and FucT2 alleles, wherein said TAL effector endonuclease-induced mutations were induced by: (a) a first TAL effector endonuclease that binds to a first pair of nucleic acid sequences selected from the group consisting SEQ ID NOs: 47 and 48, SEQ ID NOs: 49 and 50, and SEQ ID NOs: 51 and 52, each of said first pair of nucleic acid sequences located in the plurality of XylT1 and XylT2, and a second TAL effector endonuclease that binds to a second pair of nucleic acids consisting SEQ ID NOs: 53 and 54, SEQ ID NOs: 55 and 56, SEQ ID NOs: 57 and 58, SEQ ID NOs: 58 and 59, and SEQ ID NOs: 62 and 63, each of said second pair of nucleic acid sequences located in the plurality of FucT1 and FucT2 alleles,

wherein the reduced levels of beta-1,2-xylosyl-sugars and core alpha-1,3-fucosyl-sugars on said N-glycan structures of glycoproteins produced in said plant or plant cell are compared to a corresponding plant or plant cell that does not contain said TAL effector endonuclease-induced mutations.

18. The plant or plant cell of claim 17 , wherein said plant or plant cell comprises a nucleic acid encoding a heterologous polypeptide.

19. The plant or plant cell of claim 17 , wherein each of said mutations is a deletion of more than one nucleotide.

20. The plant or plant cell of claim 17 , wherein said first TAL effector endonuclease binds to SEQ ID NOS: 51 and 52, and wherein said second TAL effector endonuclease binds to SEQ ID NOS: 58 and 59.