Page 172 - Advances in Textile Biotechnology

Engineering of plants for improved fi bre qualities 153

B1A) has led to increased resistance to cold and drought stress (Behnam
et al., 2007, Kasuga et al., 2004). Interestingly, one of the most important
commercially available engineered plant species in the world is Bacillus

thuringiensis (Bt)-cotton. This fibre-plant has been modified to express the
bacterial gene Cry1Ac (from Bacillus thuringiensis) that is responsible for
the production of an endotoxin that protects cultures from insect pests
(Mendelsohn et al., 2003). Various studies have shown that the use of Bt
cotton leads to both an increase in harvest yield (and hence overall fi bre
production) and a reduction in the use of chemical insecticides (Downes
et al., 2007; Vitale et al., 2008). Cotton has also been engineered to express
another bacterial gene that encodes the enzyme 5-enolpyruvylshikimate-3-
phosphate synthase (CP4-EPSPS) thereby conferring resistance to treat-

ment with the herbicide glyphosate and allowing efficient weed control
during culture (Nida et al., 1996, Yasuor et al., 2006). It is therefore clear
that a wide variety of different plant species can be modified in order to

improve plant growth under both optimal and sub-optimal conditions.
However, apart from cotton, such technology has not yet been used to

improve the agricultural properties of fibre plants such as flax or hemp.

Qualitative improvements of fibres depend upon targeting (modifying)
those factors that specifi cally influence quality. Fibre quality is infl uenced

by:

(1) the architecture of the fibre (length, diameter, cell-wall thickness) and
(2) the composition/structure of the plant cell wall.
It is these two factors that determine the resulting physicochemical and
mechanical properties (such as tensile strength, fl exibility, hydrophobicity).
Potential plant improvement programmes aimed at improving fi bre quality
should therefore target genes implicated in regulating these two parame-
ters. In addition, another very important target concerns those components

of the cell wall that potentially hinder fibre extraction from the plant and

subsequent (elementary) fibre separation. In this chapter, we mainly address
the use of engineering to improve fi bre quality.

7.2.2 Fibre quality and genes
However, before addressing the question of how to improve fi bre quality,
it is necessary to explain (for the non-biologists) the link between genes

and fibre quality. As stated above, fibre quality depends upon both fi bre

architecture (length, diameter, cell wall thickness) and fibre cell wall com-
position. Fibres are biological structures (cells) and, as with individual
human cells, the formation and development of these cells depend upon the
biological information contained in the genes present in the DNA of the
chromosomes. For example, genes encoding a pectin methyl esterase enzyme

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