introduction of multiple genes of interest and selection. This system is useful for
transferring DNA segments of 150–200 kb (Hamilton 1997; Liu et al. 1999).
There are also methods of direct transfer of high capacity that use protective
structures such as calcium alginate particles for encapsulating the DNA (Sone
et al. 2002). This method enables introduction of DNA fragments up to 200 kb;
however, it is not compatible with biolistic transformation, its efficiency is low,
and it is not applicable in large-scale experiments (Wada et al. 2009).
The use of biolistic and A. tumefaciens has allowed the genetic manipulation of
different plants of commercial interest. However, these methods have several limitations with the insertion of multiple genes, which occurs in an uncoordinated way,
disrupting the integrity of the host genome. The limitations stimulated the development of plant mini-chromosomes which enable transfer of genetic complexes and
multiple genes, along with regulatory elements for safe expression. These minichromosomes must contain artificial telomeres, centromeres, a replication origin,
and an insertion site for genes of interest and regulatory ones (Yu et al. 2007).
This technology allows the transfer of DNA of the order of Mb but has only been
successfully applied to maize.
The most important application for the transfer of multiple genes is that they
can create or modify metabolic pathways, which may include one or multiple
genes to produce a specific metabolite. One of the most ambitious studies in this
area was the production of b-carotene in rice. Carotenogenic genes with a marker
gene were introduced in a single transformation event to produce what is now
known as the ‘‘Golden rice’’ (Ye et al. 2000). Another study highlights the production of polyunsaturated fatty acids of long chain in mustard, using nine
microbial genes encoding desaturases and elongases, through co-transformation
with A. tumefaciens (Wu et al. 2005).
15.4 Metabolic Engineering
Metabolic engineering, defined as the manipulation of enzymatic processes, that
enables the production of new compounds in an organism, improves their production, or prevents its degradation (DellaPenna 2001). The goal of metabolic
engineering is overproduction of specific compounds; however, the interconnection of metabolic pathways is huge and the number of possible ways for metabolite
manipulation is enormous (Woolston et al. 2013). The requisites for metabolic
engineering process are manipulation of a target compound, make it thermodynamically favorable and not toxic, and have the enzymes required for expression
of those metabolites in the host organism (Pickens et al. 2011).
Metabolic engineering uses Biochemistry and molecular biology, to alter the
metabolic pathways, and statistical tools for data analysis along with bioinformatics for designing, analyzing, and predicting the behavior of metabolic fluxes in
a new route. Thanks to this technology, it is known that at least 100,000 secondary
15 Plants as Bioreactors for Human Health Nutrients
429
transferring DNA segments of 150–200 kb (Hamilton 1997; Liu et al. 1999).
There are also methods of direct transfer of high capacity that use protective
structures such as calcium alginate particles for encapsulating the DNA (Sone
et al. 2002). This method enables introduction of DNA fragments up to 200 kb;
however, it is not compatible with biolistic transformation, its efficiency is low,
and it is not applicable in large-scale experiments (Wada et al. 2009).
The use of biolistic and A. tumefaciens has allowed the genetic manipulation of
different plants of commercial interest. However, these methods have several limitations with the insertion of multiple genes, which occurs in an uncoordinated way,
disrupting the integrity of the host genome. The limitations stimulated the development of plant mini-chromosomes which enable transfer of genetic complexes and
multiple genes, along with regulatory elements for safe expression. These minichromosomes must contain artificial telomeres, centromeres, a replication origin,
and an insertion site for genes of interest and regulatory ones (Yu et al. 2007).
This technology allows the transfer of DNA of the order of Mb but has only been
successfully applied to maize.
The most important application for the transfer of multiple genes is that they
can create or modify metabolic pathways, which may include one or multiple
genes to produce a specific metabolite. One of the most ambitious studies in this
area was the production of b-carotene in rice. Carotenogenic genes with a marker
gene were introduced in a single transformation event to produce what is now
known as the ‘‘Golden rice’’ (Ye et al. 2000). Another study highlights the production of polyunsaturated fatty acids of long chain in mustard, using nine
microbial genes encoding desaturases and elongases, through co-transformation
with A. tumefaciens (Wu et al. 2005).
15.4 Metabolic Engineering
Metabolic engineering, defined as the manipulation of enzymatic processes, that
enables the production of new compounds in an organism, improves their production, or prevents its degradation (DellaPenna 2001). The goal of metabolic
engineering is overproduction of specific compounds; however, the interconnection of metabolic pathways is huge and the number of possible ways for metabolite
manipulation is enormous (Woolston et al. 2013). The requisites for metabolic
engineering process are manipulation of a target compound, make it thermodynamically favorable and not toxic, and have the enzymes required for expression
of those metabolites in the host organism (Pickens et al. 2011).
Metabolic engineering uses Biochemistry and molecular biology, to alter the
metabolic pathways, and statistical tools for data analysis along with bioinformatics for designing, analyzing, and predicting the behavior of metabolic fluxes in
a new route. Thanks to this technology, it is known that at least 100,000 secondary
15 Plants as Bioreactors for Human Health Nutrients
429