Biology Reference
In-Depth Information
the stability of supply, and a closer relationship between supply and
demand. In some cases, the production of secondary metabolites
by using large-scale cell cultures is technically feasible, when the
generation and maintenance of cell biomass are achieved together
with a high yield in the production of these metabolites. However,
in some cases, the use of SCC is limited by the economy of the
process determined by the low yields of secondary metabolite
production obtained. To increase the production of secondary
metabolites using SCC as cell factories, different approaches have
extensively been used such as the screening and selection of high-
producing cell lines, cell immobilization, optimization of culture
conditions and feeding, and elicitation. Also, genetic modifi cation or
metabolic engineering are promising biotechnological approaches
to improve the production of these compounds [
2
,
3
].
Similarly, SCC has been extensively used to study the signaling
pathways involved in plant defense against several elicitors. In fact,
the use of SCC has allowed the identifi cation of numerous early
events and proteins or genes involved in the signaling cascades
immediately downstream of elicitor perception [
4
]. Early events,
such as protein phosphorylation or activation of plasma membrane
proteins, mobilize or generate directly or indirectly diverse signal-
ing molecules (such as free calcium, nitric oxide, and active oxygen
species) which regulate many processes, interconnecting branch
pathways that amplify and specify the physiological response
through transcriptional and metabolic changes [
5
].
In the same way, SCC has been used as potential production
systems of a wide range of recombinant proteins [
6
]. Like microbes,
SCC is inexpensive to grow and maintain, and they can be culti-
vated easily in large-scale bioreactors [
7
,
8
] and because they are
higher eukaryotes they can carry out many of the posttranslational
modifi cations that occur in human cells. Also, they can synthesize
complex proteins and glycoproteins, such as immunoglobulins
[
9
,
10
] and interleukins [
11
]. Perhaps, the most important advan-
tage of SCC over the use of the whole plant for the production of
recombinant proteins is the much simpler procedure for product
isolation and purifi cation [
12
-
14
] especially when the product is
secreted into the culture medium. This means that good manufac-
turing practice could be implemented throughout the production
pipeline [
6
]. Although no recombinant proteins have yet been
produced commercially using SCC, there have been many proof-
of-principle studies and several companies are investigating the
commercial feasibility of such production systems.
On the other hand, plant cells secrete a variety of proteins into
the extracellular space or bind to the cell wall [
15
-
17
]. The function
of extracellular space is crucial for plant life since it includes pro-
cesses related with growth, tissue structure, defense against
biotic and abiotic stress factors, transport, osmoregulation, cell
adhesion, and gas exchange [
18
]. Therefore, the cell wall is
