ABSTRACT
Genetically engineered plants have varied applications in agriculture for enhancing the values of food and feed.Genetic engineering aims to introduce selected genetic regions with desirable traits into target plants for bothspatial and temporal expressions. Promoters are the key elements responsible for regulating gene expressionsby modulating the transcription factors (TFs) through recognition of RNA polymerases. Based on theirrecognition and expression, RNA polymerases were categorized into RNA pol II and pol III promoters.Promoter activity and specificity are the two prime parameters in regulating the transgene expression. Since theuse of constitutive promoters like Cauliflower mosaic virus (CaMV) 35S may lead to adverse effects on nontarget organisms or ecosystem, inducible/tissue specific promoters and/or the RNA pol III promoters providemyriad opportunities for gene expressions with controlled regulation and with minimum adverse effects.Besides their role in transgene expression, their influence in synthetic biology and genome editing are alsodiscussed. This review provides an update on the importance, current prospects, and insight into the advantagesand disadvantages of promoters reported thus far would help to utilize them in the endeavour to developnutritionally and agronomically improved transgenic crops for commercialization.
ABSTRACT
Modification of transformation systems with a set of markers is almost used to confirm whether the transgene has been successfully transmitted to the host cells. Transient expression technique is a fast and simple way to analyze promoter expression. This method is not affected by the position of the transgene in the target genome. In the present study, the gus reporter gene directed by the CaMV 35S promoter and the nptII selectable gene were used for optimization of transformation event in sugar beet. The results demonstrated the activity of β-glucuronidase in the Agrobacterium cells showing suppressed expression of the prokaryotic reporter gene. The function of the pCAMBIA2301 vector was assessed through inoculation of shoot apex with Agrobacterium. The results demonstrated that cells adjacent to the main vein of leave reared from tissue cultured apical meristems were suitable for transformation and regeneration. The highest shoot regeneration was achieved for tissue-cultured leaf explants grown in the presence of BA, IBA and TDZ media. In this study, an improved protocol for regeneration and genetic engineering of a sugar beet genotype was described using the tested vector. Analysis of GUS Histochemical and polymerase chain reaction (PCR) of the T0 generation plants demonstrated that the tested vector enables the expression of the gus gene in the transgenic plants that was an evidence of transient expression.