Promoter diversity in multigene transformation

Abstract

Multigene transformation (MGT) is becoming routine in plant biotechnology as researchers seek to generate more complex and ambitious phenotypes in transgenic plants. Every nuclear transgene requires its own promoter, so when coordinated expression is required, the introduction of multiple genes leads inevitably to two opposing strategies: different promoters may be used for each transgene, or the same promoter may be used over and over again. In the former case, there may be a shortage of different promoters with matching activities, but repetitious promoter use may in some cases have a negative impact on transgene stability and expression. Using illustrative case studies, we discuss promoter deployment strategies in transgenic plants that increase the likelihood of successful and stable multiple transgene expression.

Cis-regulatory elements used to control gene expression in plants

“…The analysis of promoters formed of various CaMV 35S subdomain combinations revealed miscellaneous activity in distinct tissues (Benfey et al 1990). It proves the specific character of several subdomains (Peremarti et al 2010). CaMV 35S is more frequently used in transformation of dicots, as it is more efficient in those plants as compared to monocots.…”

“…1). Both these regions contain cis elements, which proteins, known as trans factors may bind to (Klug and Cummings 2003;Peremarti et al 2010;Porto et al 2014).…”

“…Diverse availability of transcription factors in various tissues provides this opportunity. Thereupon some promoters are constitutive, while the others may be tissue-specific or inducible (Peremarti et al 2010). Identification of enhancers acting in both directions or under certain conditions is exceptionally important for plant biotechnology, as it may facilitate construction of valuable artificial promoters.…”

“…It may be a result of distinct transcription factors availability in the foregoing groups of plants (Urwin et al 1997;McCarter 2009). Expression of genes controlled by the CaMV 35S promoter may be disturbed when the plant is infected with nematodes (Peremarti et al 2010). In spite of the mainly constitutive character, CaMV 35S activity may be lower in some tissues or organs, such as generative organs (Porto et al 2014).…”

Nutritionally Enhanced Staple Food Crops

“…However, use of transgene still has some practical limitations, for example, mechanism and pattern of gene integration, dosage effect due to variable copy insertion, interaction between transgenes, rearrangements and silencing, promoter choice as a function of gene number (i.e., one promoter vs. more promoters when integrating multiple genes) as repetitive promoters may in some cases have negative impact on transgene stability and expression, or proper coordination of all enzymes involved in the metabolic pathway. Transfer of an incomplete pathway induces significant changes in plant morphology, variable expression of transgene effects in different generation and some lines with more expression than others in later generations etc (Kristensen et al 2005;Naqvi et al 2009a, b;Dietz-Pfeilstetter 2010;Peremarti et al 2010).…”