Environmental Engineering Reference
In-Depth Information
Genetic transformation of jatropha is still in the developmental stage because not many genes
of significant value have been incorporated through genetic engineering. More research is needed
in jatropha to make this crop more reliable as a bioenergy source. Currently, the germplasm avail-
able has many setbacks, including the lack of genetic information, poor yields, vulnerability to
pests, and low genetic diversity. Areas of improvement should focus on improving yields, higher
oil content, and achieving faster maturity and enhanced fuel properties (Sujatha et al. 2008).
Agrobacterium- mediated transformation has been performed with the SaDREBI gene, with the
bar gene for selection on phosphinothricin and gus as a reporter gene (Sujatha et al. 2008). Genes
such as curcin and stearoyl-acyl carrier protein denaturase and JcERF (demonstrating salt and frost
tolerance) have been identified. Most recently, the jatropha genome (~400 million base pairs) has
been sequenced by a collaborative effort between Synthetic Genomics, Inc. (SGI) and the Asiatic
Centre for Genome Technology (ACGT) (http://checkbiotech.org/node/26008). A high-quality
normalized cDNA library using developing jatropha seeds has been developed by Natarajan et al.
(2010). Li et al. (2008) have demonstrated Agrobacterium -mediated transformation of jatropha,
and Purkayastha et al. (2010) have demonstrated genetic transformation of jatropha using a particle
bombardment method. These technologies will be useful in speeding up the genetic engineering
process of jatropha.
3.5.2.3 canola
The genus Brassica consists of approximately 100 species including Brassica napus (canola),
which is believed to have originated in the Mediterranean region or in northern Europe. Through
breeding, excellent varieties of canola lines have been developed in the Organisation for Economic
Co-operation and Development (OECD) countries (OECD Paris 1997). Edible oil, low in erucic
acid, was first extracted in Canada in 1956 (Colton and Potter 1999). Canola is currently grown for
its seeds, which yield from 35% to more than 45% oil. Canola oil is an excellent cooking oil and can
be used to manufacture biodiesel through enzymatic and chemical processes (Dizge and Keskinler
2008; Issariyakul et al. 2008; Cheng et al. 2010). The remaining by-product after seed oil extraction,
canola seed meal, is used as a high-protein animal feed.
Canola is highly amenable to in vitro manipulations, including tissue culture and genetic engi-
neering. Transformation efficiency of canola was improved to make a working protocol that suits
multiple cultivars (Cardoza and Stewart 2004, 2007; Bhalla and Singh 2008). Canola has been
genetically engineered using Agrobacterium to impart herbicide-resistance to imidazoline, glufos-
inate, glyphosate, sulfonylurea, and bromoxynil (Blackshaw et al. 1994; Zhong et al. 1997; Cardoza
and Stewart 2007). Canola became the number one crop of Canada because of the use of GM
canola. The Canola Council of Canada provides a wide variety of information on the significance
of GM canola (http://www.canolacouncil.org/facts_gmo.aspx). Oleic acid level in B. napus was
increased by silencing the endogenous oleate desaturase gene (Stoutjesdijk et al. 2000). Canola
that can produce high levels of γ-linolenic acid was achieved by introducing δ12-desaturase genes
from the fungus Mortierella alpina (Liu et al. 2001). Transgenic canola with elevated levels of
stearate content was obtained by the overexpression of the Garm FatA1 , an acyl-carrier protein
(ACP) thioesterase, isolated from Garcinia mangostana (Hawkins and Kridl 1998). The seed-
specific mutants derived from engineering Garm FatA1 gene resulted in transgenic plants that can
accumulate 55-58% more stearate than the wild-type plants (Facciotti et al. 1999). In addition,
these lines also showed an increase in laurate at the sn-2 position (Knutzon et al. 1999). Because
there are increasing pest problems in canola cultivation, insect resistance is a target trait for genetic
improvement. For example, canola is very susceptible to the diamond back moth. Halfhill et al.
(2000) introduced Bt toxin through the Bt cr y1A(c) gene to B. napus to develop insect-resistant
canola. The B. napus genome has been sequenced recently, and a sequence-level comparative
analysis at the scale of the complete bacterial artificial chromosome (BAC) clones was conducted
(Cho et al. 2010).
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