Recombinant milk proteins

1. A recombinant fusion protein, comprising:

a) full-length κ-casein or para-κ-casein; and

b) β-lactoglobulin.

2. The recombinant fusion protein of claim 1 , wherein the fusion protein comprises, in order from N-terminus to C-terminus, the full-length κ-casein or the para-κ-casein and the β-lactoglobulin.

3. The recombinant fusion protein of claim 1 , further comprising a protease cleavage site.

4. The recombinant fusion protein of claim 3 , wherein the protease cleavage site is a chymosin cleavage site.

5. The recombinant fusion protein of claim 1 , further comprising a signal peptide.

6. The recombinant fusion protein of claim 5 , wherein the signal peptide is located at the N-terminus of the fusion protein.

7. The recombinant fusion protein of claim 1 , wherein the fusion protein comprises the full-length κ-casein.

8. The recombinant fusion protein of claim 1 , wherein the fusion protein comprises para-κ-casein.

9. The recombinant fusion protein of claim 1 , wherein the fusion protein has a molecular weight of 30 kDa to 50 kDa.

10. A plant transformed to express the recombinant fusion protein of claim 1 , wherein the fusion protein is expressed in the plant in an amount of 1% or higher per total protein weight of soluble protein extractable from the plant.

11. A plant transformed to express the recombinant fusion protein of claim 1 , wherein the fusion protein is expressed in the plant at a level at least 2-fold higher than κ-casein expressed individually in a plant.

12. A plant transformed to express the recombinant fusion protein of claim 1 , wherein the fusion protein accumulates in the plant at least 2-fold higher than κ-casein expressed without β-lactoglobulin.

13. A fusion protein comprising κ-casein and β-lactoglobulin, wherein the κ-casein is full-length κ-casein comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 4 or the κ-casein is para-κ-casein comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 2 and wherein the β-lactoglobulin is full-length β-lactoglobulin comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 10.

14. The fusion protein of claim 13 , wherein the κ-casein is full-length κ-casein comprising an amino acid sequence SEQ ID NO: 4.

15. The fusion protein of claim 13 , wherein the κ-casein is para-κ-casein comprising an amino acid sequence SEQ ID NO: 2.

16. The fusion protein of claim 13 , wherein the β-lactoglobulin comprises the amino acid sequence SEQ ID NO: 10.

17. The fusion protein of claim 13 , further comprising a protease cleavage site between the κ-casein and β-lactoglobulin.

18. The fusion protein of claim 17 , wherein the protease cleavage site is a chymosin cleavage site.

19. The fusion protein of claim 13 , further comprising a signal peptide.

20. A nucleic acid molecule encoding a fusion protein comprising κ-casein and β-lactoglobulin, wherein the κ-casein is full-length κ-casein comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 4 or the κ-casein is para-κ-casein comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 2 wherein the β-lactoglobulin is full-length β-lactoglobulin comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 10.

21. The nucleic acid molecule of claim 20 , wherein the nucleic acid sequence is codon optimized for expression in a plant.

22. The nucleic acid molecule of claim 21 , wherein the plant is soybean.

23. An expression vector comprising the nucleic acid molecule of claim 20 .

24. A host cell comprising the expression vector of claim 23 .

25. The host cell of claim 24 , wherein the host cell is selected from the group consisting of plant cells, bacterial cells, fungal cells, and mammalian cells.

26. The host cell of claim 25 , wherein the host cell is a plant cell.

27. A plant stably transformed with the nucleic acid molecule of claim 20 .

28. The plant of claim 27 , wherein the plant is a monocot selected from the group consisting of turf grass, maize, rice, oat, wheat, barley, sorghum, orchid, iris, lily, onion, palm, and duckweed.

29. The plant of claim 27 , wherein the plant is a dicot selected from the group consisting of Arabidopsis, tobacco, tomato, potato, sweet potato, cassava, alfalfa, lima bean, pea, chick pea, soybean, carrot, strawberry, lettuce, oak, maple, walnut, rose, mint, squash, daisy, quinoa, buckwheat, mung bean, cow pea, lentil, lupin, peanut, fava bean, French beans, mustard, and cactus.

30. The plant of claim 29 , wherein the plant is soybean.

31. The plant of claim 27 , wherein the plant is a non-vascular plant selected from the group consisting of moss, liverwort, hornwort, and algae.

32. The plant of claim 27 , wherein the plant is a vascular plant reproducing from spores.

33. A method for stably expressing a recombinant fusion protein comprising κ-casein and β-lactoglobulin in a plant,

wherein the κ-casein is full-length κ-casein comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 4 or the κ-casein is para-κ-casein comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 2 and wherein the β-lactoglobulin is full-length β-lactoglobulin comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 10,

said method comprising:

(i) transforming a plant with a plant transformation vector comprising an expression cassette comprising a nucleic acid molecule encoding the fusion protein; and

(ii) growing the transformed plant under conditions wherein the recombinant fusion protein is expressed.

34. The method of claim 33 , wherein the fusion protein is expressed in an amount of 1% or higher per the total protein weight of the soluble protein extractable from the plant.

35. The method of claim 33 , wherein the fusion protein is expressed in the plant at a level at least 2-fold higher than κ-casein expressed individually in a plant.

36. The method of claim 33 , wherein the fusion protein accumulates in the plant at least 2-fold higher than κ-casein is expressed without β-lactoglobulin.

37. A food composition comprising a fusion protein comprising κ-casein and β-lactoglobulin, wherein the κ-casein is full-length κ-casein comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 4 or the κ-casein is para-κ-casein comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 2 and wherein the β-lactoglobulin is full-length β-lactoglobulin comprising an amino acid sequence having at least 90% sequence identity to SEQ ID NO: 10.

38. The food composition of claim 37 , wherein the food composition is selected from the group consisting of cheese and processed cheese products, yogurt and fermented dairy products, directly acidified counterparts of fermented dairy products, cottage cheese dressing, frozen dairy products, frozen desserts, desserts, baked goods, toppings, icings, fillings, low-fat spreads, dairy-based dry mixes, soups, sauces, salad dressing, geriatric nutrition, creams and creamers, analog dairy products, follow-up formula, baby formula, infant formula, milk, dairy beverages, acid dairy drinks, smoothies, milk tea, butter, margarine, butter alternatives, growing up milks, low-lactose products and beverages, medical and clinical nutrition products, protein/nutrition bar applications, sports beverages, confections, meat products, analog meat products, meal replacement beverages, weight management food and beverages, cultured buttermilk, sour cream, yogurt, skyr, leben, lassi, kefir, powder containing a milk protein, and low-lactose products.