Difference between revisions of "Part:BBa K3758000"

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Prrn16, rrn16 Promoter (-64 to +17) (N. tabacum)

Part Description

This part was created using the Phytobrick Entry Vector with GFP dropout BBa_K2560002 and was designed to be compatible with the Phytobrick assembly standard. All parts created this year were acquired via PCR from purified DNA samples using a CTAB based method [1], by primer annealing, primer annealing, and extension reactions or synthesized via IDT/Twist.

All parts this year were produced to be used in the chloroplast of different plant species. For the characterization of these parts they were tested in chloroplast cell-free systems (ccfs) from either the same species or they were tested in ccfs from other plant species. Plastid parts offer the benefit of highly conserved regulatory sequences that can be used across species. Although characterizing chloroplast parts is a huge effort, in literature, it has been shown that plastid parts can be used across species to drive gene expression [2]. We believe that based on this knowledge we can create valuable parts that can be screened for activity in our system with the final goal of building a variety of different parts. This collection shall help combat unwanted recombination events in vivo that sometimes impede the successful functionality of the genetic design.

The PEP Promoter

Transcription in the chloroplast is mainly driven by two different RNA Polymerases: plastid-encoded polymerase (PEP) and nuclear-encoded polymerase (NEP).
The PEP is a bacterial-like polymerase that is a remnant of the chloroplast’s cyanobacterial ancestor and is only capable of promoting gene expression in the plastid. These polymerases are able to interact with nuclear-encoded sigma factors and therefore are able to recognize bacterial promoter motives such as the -35 (TTGACA) and the Pribnow (TATAAT) box. Similar to bacteria there are different sigma factors promoting gene expression under different growth conditions. As the PEP is structurally more sophisticated there are even more peptides involved in DNA transcription that is not fully understood yet.

The NEP Promoter

The NEP is a T3/T7 phage-like polymerase that is encoded in the nucleus and is imported into the chloroplast. It was proposed that this polymerase is a remnant of a horizontal gene transfer from a bacterium to a eubacterial ancestor of today's plant cells [3], [4]. This type of polymerase mainly promotes gene expression in the early developmental stages of the chloroplast. In mature chloroplasts, it continues to transcribe housekeeping genes like the subunits of the plastid-encoded polymerase (rpoA, rpoB, rpoC1, and rpoC2) and proteins involved in fatty acid biosynthesis such as acetyl-CoA carboxylase (accD). In contrast, the PEP is rather active in mature chloroplasts and is primarily involved in the expression of photosynthetic genes. For other non-photosynthetic genes, motives of both polymerases can be found and it has been shown that both can promote transcription using deletion studies of important promoter sequences [5], [6].

Sequence and Features

References

[1] Aboul-Maaty, N. A.-F., & Oraby, H. A.-S. (2019). Extraction of high-quality genomic DNA from different plant orders applying a modified CTAB-based method. Bulletin of the National Research Centre, 43(1). https://doi.org/10.1186/s42269-019-0066-1

[2] Fuentes, P., Zhou, F., Erban, A., Karcher, D., Kopka, J., & Bock, R. (2016). A new synthetic biology approach allows transfer of an entire metabolic pathway from a medicinal plant to a biomass crop. ELife, 5. https://doi.org/10.7554/elife.13664

[3] Filée, J., & Forterre, P. (2005). Viral proteins functioning in organelles: a cryptic origin? Trends in Microbiology, 13(11), 510–513. https://doi.org/10.1016/j.tim.2005.08.012

[4] Liere, K., & Börner, T. (2007). Transcription and transcriptional regulation in plastids. In Cell and Molecular Biology of Plastids (pp. 121–174). Springer Berlin Heidelberg. https://doi.org/10.1007/4735_2007_0232

[5] Xie, G., & Allison, L. (2002). Sequences upstream of the YRTA core region are essential for transcription of the tobacco atpB NEP promoter in chloroplasts in vivo. Current Genetics, 41(3), 176–182. https://doi.org/10.1007/s00294-002-0293-z

[6] Kuroda, H., & Maliga, P. (2002). Overexpression of the clpP 5′-Untranslated Region in a Chimeric Context Causes a Mutant Phenotype, Suggesting Competition for a clpP-Specific RNA Maturation Factor in Tobacco Chloroplasts. Plant Physiology, 129(4), 1600–1606. https://doi.org/10.1104/pp.004986

[7] Suzuki, J. Y., Sriraman, P., Svab, Z., & Maliga, P. (2003). Unique Architecture of the Plastid Ribosomal RNA Operon Promoter Recognized by the Multisubunit RNA Polymerase in Tobacco and Other Higher Plants. The Plant Cell, 15(1), 195–205. https://doi.org/10.1105/tpc.007914

[8] Occhialini, A., Piatek, A. A., Pfotenhauer, A. C., Frazier, T. P., Stewart, C. N., Jr., & Lenaghan, S. C. (2019). MoChlo: A Versatile, Modular Cloning Toolbox for Chloroplast Biotechnology. Plant Physiology, 179(3), 943–957. https://doi.org/10.1104/pp.18.01220