In PCC there are several strategies to increase production of secondary
metabolites, like production of fast growing cell lines, immobilization of cells in
polymers, use of elicitors to accelerate the production of a given metabolite
membrane permeation to facilitate diffusion of metabolites, scaling of cell culture
bioreactors, and genetic engineering for production of specific metabolites
(Oksman-Caldentey and Inzé 2004).
15.2.1 Plant Cell Culture (Somaclonal Variation)
Somaclonal variation is generated by genetic modification of in vitro culture, which
manifests as inheritable mutations in regenerated seedlings (Larkin and Scowcroft
1981). The term somaclonal variation is used universally for all variants of PCC
(Bajaj 1990), and is described as one of the major problems in the regeneration of
plants grown in vitro. Plant cell growth in vitro is an asexual process that involves
only mitotic cell division and theoretically should not cause any mutation (Larkin
1998). However, these mutational effects have utility in improving the crop through
the creation of novel plant varieties with characteristics that could increase their
commercial value such as disease resistance, improved biomass yield, and
increased production of secondary metabolites (Karp 1994).
15.2.1.1 Causes of Somaclonal Variation
Unlike in vivo mutations, in vitro mutations occur more frequently and are more
easily detected observing variants found in the regenerated plant in a short period of
time. Mutations may occur because of exposure of plant tissue to the chemical
compounds of the culture medium, the habituation to a new hormone balance (like
auxin and cytokinin ratios), and the process in which the plant material is rearranged
to form a new organ. Even some plantlets could express the natural variation already
present in somatic cells before the PCC modifies the cell cycle pathways and causes
transposon insertions and chromosomal aberrations (Vasil 1990). For PCC-based
approaches it has to be considered that somaclonal variation may be present in the
nuclear, mitochondrial, and chloroplast DNA (Aversano et al. 2009).
15.2.1.2 Methods for Detecting Somaclonal Variations
Somaclonal variation could be a major problem in operating large-scale micropropagation, whereby early detection and elimination of variants is essential to
reduce losses to the producers. Detection of variations is also used to find lines with
useful agronomic treats and production of compounds with commercial interest
(Karp 1995). Several types of techniques for detecting somaclonal variations are
from molecular, biochemical, and morphological characteristics. Morphological
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L. A. Cruz-Ramírez et al.
metabolites, like production of fast growing cell lines, immobilization of cells in
polymers, use of elicitors to accelerate the production of a given metabolite
membrane permeation to facilitate diffusion of metabolites, scaling of cell culture
bioreactors, and genetic engineering for production of specific metabolites
(Oksman-Caldentey and Inzé 2004).
15.2.1 Plant Cell Culture (Somaclonal Variation)
Somaclonal variation is generated by genetic modification of in vitro culture, which
manifests as inheritable mutations in regenerated seedlings (Larkin and Scowcroft
1981). The term somaclonal variation is used universally for all variants of PCC
(Bajaj 1990), and is described as one of the major problems in the regeneration of
plants grown in vitro. Plant cell growth in vitro is an asexual process that involves
only mitotic cell division and theoretically should not cause any mutation (Larkin
1998). However, these mutational effects have utility in improving the crop through
the creation of novel plant varieties with characteristics that could increase their
commercial value such as disease resistance, improved biomass yield, and
increased production of secondary metabolites (Karp 1994).
15.2.1.1 Causes of Somaclonal Variation
Unlike in vivo mutations, in vitro mutations occur more frequently and are more
easily detected observing variants found in the regenerated plant in a short period of
time. Mutations may occur because of exposure of plant tissue to the chemical
compounds of the culture medium, the habituation to a new hormone balance (like
auxin and cytokinin ratios), and the process in which the plant material is rearranged
to form a new organ. Even some plantlets could express the natural variation already
present in somatic cells before the PCC modifies the cell cycle pathways and causes
transposon insertions and chromosomal aberrations (Vasil 1990). For PCC-based
approaches it has to be considered that somaclonal variation may be present in the
nuclear, mitochondrial, and chloroplast DNA (Aversano et al. 2009).
15.2.1.2 Methods for Detecting Somaclonal Variations
Somaclonal variation could be a major problem in operating large-scale micropropagation, whereby early detection and elimination of variants is essential to
reduce losses to the producers. Detection of variations is also used to find lines with
useful agronomic treats and production of compounds with commercial interest
(Karp 1995). Several types of techniques for detecting somaclonal variations are
from molecular, biochemical, and morphological characteristics. Morphological
426
L. A. Cruz-Ramírez et al.