resulted as key factors to improve this transformation method, as well as genotype
screening, explant type and quality, selective agents, and Agrobacterium strains
(Arencibia et al. 1998; Arencibia and Carmona, 2006; Manickavasagam et al.
2004). Importantly, Jackson et al. (2013), van der Vyver et al. (2013) and Mayavan
et al. (2013) have recently reported successful results using both transformation
methods for sugarcane.
Although no commercial transgenic sugarcane variety is available in the market
so far, genes associated with sucrose content (Papini-Terzi et al. 2009), resistance to
pests and pathogens, including constructs against insects, bacteria, and viruses
(Arencibia et al. 1997, 1999; Falco and Silva-Filho 2003; Ingelbrecht et al. 1999;
Weng et al. 2006, 2011; Zhu et al. 2011; Ismail 2013), herbicide-resistance genes as
selective markers (Manickavasagam et al. 2004) and drought tolerance (Molinari
et al. 2007) have been successfully cloned into some varieties. Besides, none of those
reports refers to plastid transformation, even though this technology is considered a
valuable tool for improving the containment of the transgene, and enhancing the
biosafety of genetically modified (GM) plants (CBU 2007; Gottschamel et al. 2013;
Ruf et al. 2007; Scortecci et al. 2012).
The inheritance of the chloroplasts in most plants is maternal, as these organelles are not carried by pollen. The manipulation of the chloroplast genome for
crop improvement is therefore a highly promising technology for biosafety reasons. There are several examples of agronomical and biotechnological applications
of plastid transformation with enhanced biosafety and higher transgene product
yields in C4 plants and green microalgae (Wang et al. 2009; Chen and Melis 2013;
Hanson et al. 2013) and new advances are being developed (Gottschamel et al.
2013). Although chloroplast genetic transformation is still very incipient in
monocots like rice (Lee et al. 2006) and wheat (Cui et al. 2011; He 2012), and it
has not been reported for sugarcane (Scortecci et al. 2012), the research avenue is
widely open since the chloroplast genome of sugarcane has been completely
sequenced (Calsa-Júnior et al. 2004), which enables recombination-based transformation with huge potential for basic and applied research in molecular
pharming.
Importantly, a repertoire of gene promoters that work efficiently and precisely
regarding level, timing, and location of expression is a critical element of transgenic cultivar development (Scortecci et al. 2012).
Public opinion currently appears to be biased against foods derived from GM
organisms, and the cane industry faces a general community rejection of sugar
produced by GM plants (Grice et al. 2003). In other industries, GM cultivars that
are environmentally friendly and not designed for human consumption (e.g.,
Bt-cotton) have been accepted reasonably well. One of the main causes of public
concern about genetic engineering has been the lack of information about the
process and the types of products, particularly nonfood products that can be
developed. As a consequence, in many countries GM sugarcane is facing release
restrictions (Grice et al. 2003; Cheavegatti-Gianotto et al. 2011; Scortecci et al.
2012), which has to be taken into consideration when designing sugarcane
5 Sugarcane as a Novel Biofactory: Potentialities and Challenges
141
screening, explant type and quality, selective agents, and Agrobacterium strains
(Arencibia et al. 1998; Arencibia and Carmona, 2006; Manickavasagam et al.
2004). Importantly, Jackson et al. (2013), van der Vyver et al. (2013) and Mayavan
et al. (2013) have recently reported successful results using both transformation
methods for sugarcane.
Although no commercial transgenic sugarcane variety is available in the market
so far, genes associated with sucrose content (Papini-Terzi et al. 2009), resistance to
pests and pathogens, including constructs against insects, bacteria, and viruses
(Arencibia et al. 1997, 1999; Falco and Silva-Filho 2003; Ingelbrecht et al. 1999;
Weng et al. 2006, 2011; Zhu et al. 2011; Ismail 2013), herbicide-resistance genes as
selective markers (Manickavasagam et al. 2004) and drought tolerance (Molinari
et al. 2007) have been successfully cloned into some varieties. Besides, none of those
reports refers to plastid transformation, even though this technology is considered a
valuable tool for improving the containment of the transgene, and enhancing the
biosafety of genetically modified (GM) plants (CBU 2007; Gottschamel et al. 2013;
Ruf et al. 2007; Scortecci et al. 2012).
The inheritance of the chloroplasts in most plants is maternal, as these organelles are not carried by pollen. The manipulation of the chloroplast genome for
crop improvement is therefore a highly promising technology for biosafety reasons. There are several examples of agronomical and biotechnological applications
of plastid transformation with enhanced biosafety and higher transgene product
yields in C4 plants and green microalgae (Wang et al. 2009; Chen and Melis 2013;
Hanson et al. 2013) and new advances are being developed (Gottschamel et al.
2013). Although chloroplast genetic transformation is still very incipient in
monocots like rice (Lee et al. 2006) and wheat (Cui et al. 2011; He 2012), and it
has not been reported for sugarcane (Scortecci et al. 2012), the research avenue is
widely open since the chloroplast genome of sugarcane has been completely
sequenced (Calsa-Júnior et al. 2004), which enables recombination-based transformation with huge potential for basic and applied research in molecular
pharming.
Importantly, a repertoire of gene promoters that work efficiently and precisely
regarding level, timing, and location of expression is a critical element of transgenic cultivar development (Scortecci et al. 2012).
Public opinion currently appears to be biased against foods derived from GM
organisms, and the cane industry faces a general community rejection of sugar
produced by GM plants (Grice et al. 2003). In other industries, GM cultivars that
are environmentally friendly and not designed for human consumption (e.g.,
Bt-cotton) have been accepted reasonably well. One of the main causes of public
concern about genetic engineering has been the lack of information about the
process and the types of products, particularly nonfood products that can be
developed. As a consequence, in many countries GM sugarcane is facing release
restrictions (Grice et al. 2003; Cheavegatti-Gianotto et al. 2011; Scortecci et al.
2012), which has to be taken into consideration when designing sugarcane
5 Sugarcane as a Novel Biofactory: Potentialities and Challenges
141