Page 173 - Advances in Textile Biotechnology

154 Advances in textile biotechnology

and genes associated with auxin metabolism have been shown to be involved

in the control of fibre and vessel length in poplar wood (Nilsson et al., 2008;
Siedlecka et al., 2008), and actin genes and ethylene-related genes have
been shown to be involved in fi bre elongation in cotton (Li et al., 2005; Shi
et al., 2006).
Similarly, plant cell walls are a complex assembly of various polymers
(polysaccharides such as cellulose, hemicelluloses and pectins, proteins,
and the phenolic polymer lignin) (Fincher, 2009; Weng et al., 2008). These
polymers are present in different amounts (and types) depending upon the

fibre (species, tissue) and it is the variability of cell wall composition that
explains the different properties of different fi bres (McDougall et al., 1993).
For example, the secondary cell walls of fl ax fibres are unusual because they

are only weakly lignified, containing an atypical angiosperm lignin, as well
as relatively high amounts of non-cellulosic galactans (Day et al., 2005a;
Gorshkova and Morvan, 2006). The synthesis and assembly of these differ-
ent polymers into the structure that we call the cell wall are under the
control of a complex network of several hundred genes (Fincher, 2009;
Mellerowicz and Sundberg, 2008; Zhong and Ye, 2007). Up- or down-
regulating the expression (‘activity’) of various ‘cell wall genes’ provokes

modifications in the composition/structure of the plant cell wall. For
example, considerable research over the past two decades has demon-
strated that cell wall lignin content and chemical structure can be engi-
neered in both model plants and economically important species (Vanholme
et al., 2008; Weng et al., 2008).
The challenge, if we want to improve the quality of plant fibres via a

gene-based engineering approach, is therefore to identify genes and to
improve our knowledge about what genes are involved in fi bre formation
and development. Until relatively recently, identification of flax genes was

performed on an individual basis based on the assumption that, for example,

a fl ax ‘lignification gene’ would have a similar structure to the same gene

from a model plant such as Arabidopsis. Following identification, a reverse
genetics approach (in which the gene is inactivated) has been used by dif-

ferent teams to understand the role of key genes in fl ax fibre (and oil)
formation (Day et al., 2009; Fofana et al., 2006; Lacoux et al., 2003; Vrinten
et al., 2005; Wróbel-Kwiatkowska et al., 2007a). Although such studies have
provided useful information on the role of the selected gene, they are not
high-throughput approaches and do not provide large-scale genomic infor-
mation (i.e. simultaneous information about hundreds/thousands of differ-
ent genes) about these biological processes. As a result, other research
teams are now starting to develop whole transcriptome/proteome
approaches to study fibre and oil formation in flax and hemp (Day et al.,

2005b; De Pauw et al., 2007; Hotte and Deyholos, 2008; Roach and
Deyholos, 2007, 2008). Such powerful molecular tools are not only enabling

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