visible phenotype, for example flower pigments; those TFs were evaluated in
accordance to the gain or loss of that trait. The integration of genomic, metabolomic, and bioinformatic technologies change the picture resulting in the
identification of new transcription factors (Grotewold 2008).
15.5.1 Transcription Factor Expression for the Control
of a Metabolic Pathway
The regulation of metabolic pathways through ectopic expression of TFs is a tool
that allows the control of multiple genes with the introduction of a unique gene that
represents a powerful strategy in metabolic engineering (Fig. 15.1). The sequencing
of A. thaliana genome and the subsequent bioinformatic analyses suggest that more
than 5 % of the genes of this plant code for TFs; however, less than 10 % of them
have been characterized (Riechmann et al. 2000). This technology has allowed to
identify more than 50 families of TFs, like GmERF3 transcription factor in soybean
plants that belongs to AP2/ERF family. The analysis of these sequences shows that
this TF contains an AP2/ERF domain of 58 amino acids and two nuclear localization
signals (NLS). The expression of this gene was detected when the plants were
submitted to treatments with high salinity, drought, abscisic acid, salicylic acid,
jasmonic acid, ethylene, and soybean mosaic virus, but not in cold conditions (Chen
et al. 2012). The ectopic expression of GmERF3 in tobacco plants under the control
of 35 s CaMV promoter shows excellent results increasing the expression of PR
genes, improving resistance to infections caused by Ralstonia solanacearum,
Alternaria alternata, and Tobacco mosaic virus (TMV), besides increasing the
tolerance to salinity and hydric stress (Zhang et al. 2009).
15.5.2 Design of Artificial Transcription Factors
15.5.2.1 Silencing Through Chimeric Repressor Gene Silencing
Technology
Artificial transcription factors are winning impulse like metabolic engineering
tools. The fusion between a transcriptional activator with a dominant repressor
produces a repressive molecule. This process has various advantages over iRNA
silencing; in this strategy we do not control the negative expression of a single
gene, but a complete battery of genes that interfere in a specific process (Grotewold 2008). If A. thaliana were silenced by this technology, the TFs APETALA 3,
AGAMOUS, LEAFY, and AtMYB26 related with development of petals, stamens,
floral meristems, and anthers, would be placed under constitutive 35 s CaMV
promoter, which merge with SRDX sequence. The transgenic plants that express
438
L. A. Cruz-Ramírez et al.
accordance to the gain or loss of that trait. The integration of genomic, metabolomic, and bioinformatic technologies change the picture resulting in the
identification of new transcription factors (Grotewold 2008).
15.5.1 Transcription Factor Expression for the Control
of a Metabolic Pathway
The regulation of metabolic pathways through ectopic expression of TFs is a tool
that allows the control of multiple genes with the introduction of a unique gene that
represents a powerful strategy in metabolic engineering (Fig. 15.1). The sequencing
of A. thaliana genome and the subsequent bioinformatic analyses suggest that more
than 5 % of the genes of this plant code for TFs; however, less than 10 % of them
have been characterized (Riechmann et al. 2000). This technology has allowed to
identify more than 50 families of TFs, like GmERF3 transcription factor in soybean
plants that belongs to AP2/ERF family. The analysis of these sequences shows that
this TF contains an AP2/ERF domain of 58 amino acids and two nuclear localization
signals (NLS). The expression of this gene was detected when the plants were
submitted to treatments with high salinity, drought, abscisic acid, salicylic acid,
jasmonic acid, ethylene, and soybean mosaic virus, but not in cold conditions (Chen
et al. 2012). The ectopic expression of GmERF3 in tobacco plants under the control
of 35 s CaMV promoter shows excellent results increasing the expression of PR
genes, improving resistance to infections caused by Ralstonia solanacearum,
Alternaria alternata, and Tobacco mosaic virus (TMV), besides increasing the
tolerance to salinity and hydric stress (Zhang et al. 2009).
15.5.2 Design of Artificial Transcription Factors
15.5.2.1 Silencing Through Chimeric Repressor Gene Silencing
Technology
Artificial transcription factors are winning impulse like metabolic engineering
tools. The fusion between a transcriptional activator with a dominant repressor
produces a repressive molecule. This process has various advantages over iRNA
silencing; in this strategy we do not control the negative expression of a single
gene, but a complete battery of genes that interfere in a specific process (Grotewold 2008). If A. thaliana were silenced by this technology, the TFs APETALA 3,
AGAMOUS, LEAFY, and AtMYB26 related with development of petals, stamens,
floral meristems, and anthers, would be placed under constitutive 35 s CaMV
promoter, which merge with SRDX sequence. The transgenic plants that express
438
L. A. Cruz-Ramírez et al.