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1.  Development of an optimized tetracycline-inducible expression system to increase the accumulation of interleukin-10 in tobacco BY-2 suspension cells 
BMC Biotechnology  2012;12:40.
Background
Plant cell suspension cultures can be used for the production of valuable pharmaceutical and industrial proteins. When the recombinant protein is secreted into the culture medium, restricting expression to a defined growth phase can improve both the quality and quantity of the recovered product by minimizing proteolytic activity. Temporal restriction is also useful for recombinant proteins whose constitutive expression affects cell growth and viability, such as viral interleukin-10 (vIL-10).
Results
We have developed a novel, tetracycline-inducible system suitable for tobacco BY-2 suspension cells which increases the yields of vIL-10. The new system is based on a binary vector that is easier to handle than conventional vectors, contains an enhanced inducible promoter and 5′-UTR to improve yields, and incorporates a constitutively-expressed visible marker gene to allow the rapid and straightforward selection of the most promising transformed clones. Stable transformation of BY-2 cells with this vector, without extensive optimization of the induction conditions, led to a 3.5 fold increase in vIL-10 levels compared to constitutive expression in the same host.
Conclusions
We have developed an effective and straightforward molecular farming platform technology that improves both the quality and the quantity of recombinant proteins produced in plant cells, particularly those whose constitutive expression has a negative impact on plant growth and development. Although we tested the platform using vIL-10 produced in BY-2 cells, it can be applied to other host/product combinations and is also useful for basic research requiring strictly controlled transgene expression.
doi:10.1186/1472-6750-12-40
PMCID: PMC3410776  PMID: 22784336
2.  A membrane-bound matrix-metalloproteinase from Nicotiana tabacum cv. BY-2 is induced by bacterial pathogens 
BMC Plant Biology  2009;9:83.
Background
Plant matrix metalloproteinases (MMP) are conserved proteolytic enzymes found in a wide range of monocotyledonous and dicotyledonous plant species. Acting on the plant extracellular matrix, they play crucial roles in many aspects of plant physiology including growth, development and the response to stresses such as pathogen attack.
Results
We have identified the first tobacco MMP, designated NtMMP1, and have isolated the corresponding cDNA sequence from the tobacco suspension cell line BY-2. The overall domain structure of NtMMP1 is similar to known MMP sequences, although certain features suggest it may be constitutively active rather than dependent on proteolytic processing. The protein appears to be expressed in two forms with different molecular masses, both of which are enzymatically active as determined by casein zymography. Exchanging the catalytic domain of NtMMP1 with green fluorescent protein (GFP) facilitated subcellular localization by confocal laser scanning microscopy, showing the protein is normally inserted into the plasma membrane. The NtMMP1 gene is expressed constitutively at a low level but can be induced by exposure to bacterial pathogens.
Conclusion
Our biochemical analysis of NtMMP1 together with bioinformatic data on the primary sequence indicate that NtMMP1 is a constitutively-active protease. Given its induction in response to bacterial pathogens and its localization in the plasma membrane, we propose a role in pathogen defense at the cell periphery.
doi:10.1186/1471-2229-9-83
PMCID: PMC2715019  PMID: 19563670

Results 1-2 (2)