Page 175 - Advances in Textile Biotechnology

156 Advances in textile biotechnology

for ramie (Boehmeria nivea) raises the possibility of introducing desirable

traits into another fibre plant (Wang et al., 2009b).
Another powerful way of introducing genes into plants is the particle
bombardment method in which metal particles (usually gold or tungsten)
are coated with multiple copies of the desired gene and introduced directly
into tissues or cells via a special apparatus (gene gun) (Christou et al., 1988;
Klein et al., 1987; Sanford, 1990; Twyman and Christou, 2004). The main
interest of this method is that it can be used to engineer economically
important species (maize, rice, sugarcane, wheat, sorghum, papaya, spruce)
that are currently recalcitrant to transformation by Agrobacterium. More
recently (Naqvi et al., 2009), attention has been focused on introducing
several genes (multigene transfer, MGT) in order to engineer complete
metabolic pathways. Such an approach is interesting since single-gene trans-
fer is often unable to modify the physiological pathway targeted.

7.4 Some examples of engineering in fi bre species

7.4.1 Cotton

As indicated above, the most widely cultivated fibre plant is cotton
(Gossypium hirsutum L.) (Chen et al., 2007; Singh et al., 2009). Cotton fi bres
are single, long (30–40 mm), epidermal cells of the seed coat that undergo
synchronous elongation during maturation (Li et al., 2002). The elongating

fibre is highly vacuolated and its maturation is associated with secondary
cell wall formation and intensive cellulose biosynthesis, followed by dehy-

dration and mineral accumulation. The mature fibre consists mainly of
cellulose (85–90%) with the rest being composed of hemicelluloses and
pectins (4–6%), waxes and fats (0.5–1%) and proteins (0–1.5%). Cotton

fibres contain no, or extremely low amounts of, lignin and other polyphe-
nolic materials thereby explaining their white coloration (Ioelovich and

Leykin, 2008). The chemical composition of these fibres, together with their
form, as well as their relative accessibility post-harvesting, all explain the
predominant position of cotton in the textile industry.
Engineering has previously been used to increase the resistance of cotton
plants to insect attack (Mendelsohn et al., 2003) and herbicides (Yasuor

et al., 2006). More recently, a specific ‘cell-wall’-related gene has also been
targeted (Wang et al., 2009a). In this study, the down-regulation of the
GhADF1 gene that codes for an actin depolymerising factor was shown to

improve cotton fibre properties. This study indicated that the length and

strength of the transgenic fibres were higher (5.6 and 2–12%, respectively)
when compared with wild-type fibres. The secondary cell walls of modifi ed

cotton fibres were also thicker and the deposition of cellulose was increased
by 3–5% compared with control fibres. Actin is a cellular protein that makes

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