Table 4.
Examples of signal peptides, peptide tags, vectors, recombinant genes, and plant host systems employed in molecular pharming studies
| Peptide/Purpose | Vector | Expressed gene | Plant host system/yield | Reference |
|---|---|---|---|---|
| Signal peptides | ||||
| AP24 osmotin signal peptide/driving the mature protein to apoplast | pZP200 | SAG1 (surface antigen1) from Toxoplasma gondii | Tobacco leaves/1.3 μg per g FW | [71] |
| Bacterial signal peptide | pCTB-BSG | The non-toxic B subunit (CT-B) of cholera, toxin from Vibrio cholera | Maize seeds/the highest expression level in T1 generation seeds was 0.0014 % of TSP | [73] |
| Endogenous signal peptide (SPArtv1)/direct Art v 1 to the secretory pathway | pBI121 | Allergen of Artemisia vulgaris pollen, Art v 1 | Tobacco plant and cells cultures/low level (as ≥1 μg/L cell culture) | [127] |
| Prolamin signal peptide/target hGH to ER | pGH-Pi | hGH | Rice seeds/470 μg/g dry weight | [109] |
| Phaseolin signal peptide (sp) and phaseolin vacuolar sorting-signal AFVY | pBI121 | Plasmodium Falciparum merozoite surface protein (42-kDa) Malaria vaccine antigen | A. thaliana seeds/5 % of total extractable protein | [128] |
| Peptide tag | ||||
| Elastin-like polypeptides/stability and purification | pCB301 | HIV-neutralizing antibodies 2G12 (light or heavy chain) | Tobacco transgenic plants/1 % TSP in leaves and seeds | [8, 129] |
| BASB/cell wall, vacuole targeting | Codon-optimized heat-stable HBsAg gene | Maize seeds/0.31 % TSP (BASB) and 0.12 % TSP | [75] | |
| Hydrophobin HFBI gene from Trichoderma reesei/change hydrophobicity of partner | pCaMterX | GFP–HFBI fusion accumulate and backed into protein bodies | Transiently agro-infiltrated Tobacco/51 % of TSP, 91 % recovery of GFP–HFBI fusion protein (10 mg/mL) | [130, 131] |
| SBA/full ORF as a tag for purification | PBI101 | GFP fused to ORF of SBA | Tobacco leaves/2.5 % of TSP and 90 % purification efficiency using N-acetyl-d-galactosamine-agar columns | [84] |
| Tamavidin 2/fungal avidin-like protein that binds biotin with high affinity, a versatile affinity tag | pSP24 | SBA–tamavidin (SBA-S-TM2) fusion | Tobacco By-2 cells 2 mg/L highly purified (90–95 % purity) on the microbeads | [132] |
| Thrombin protease/cleavage site | PTZ57 | Human interferon-α5 | Tobacco chloroplasts/4,372 pg/g FW | [79] |
BASB barley amylase signal peptide, CT-B cholera toxin B subunit, ER endoplasmic reticulum, FW fresh weight, GFP green fluorescence protein, HBsAg hepatitis B surface antigen, HFBI hydrophobin, hGH human growth hormone, ORF open reading frame, SBA soybean agglutinin, TSP total soluble protein