Biomedical Engineering Reference
In-Depth Information
fiber characters. Fiber elongation also relies on the cleavage of sucrose into UDP-
glucose and fructose to increase osmotic pressure. These compounds also provide
the substrate for cellulose synthesis during later SCW thickening. Sucrose synthase
is a key enzyme in this reaction and is abundant in fiber initials [
92
,
93
]. A novel
cotton sucrose synthase gene,
GhSusA1
, was identified from
G. hirsutum
. Silencing
of
GhSusA1
reduced fiber length and yield, whereas overexpression of this gene
increased fiber length and strength [
94
]. Additionally, overexpression of a potato
sucrose synthase in transgenic cotton enhanced leaf expansion and improved early
seed development, thereby enhancing seed set and promoted fiber elongation
[
95
]. Both of these studies suggest that sucrose synthase is an important regulator
of sink strength in cotton that is tightly associated with productivity. It is therefore a
promising candidate gene that can be developed to increase cotton fiber yield and
quality - possibly by improving seed development as a whole, rather than solely
focusing on manipulating fiber growth [
95
]. Cellulose synthesis is a key biochem-
ical event during SCW formation, and at least five cellulose synthase (
CesA
) genes
have been shown to increase in expression during this stage [
96
], so increasing
cellulose production is an obvious target for improving fiber quality. The fibers
from transgenic cotton expressing two cellulose synthase genes (
acsA
and
acsB
),
from the bacterium
Acetobacter xylinum
, were approximately 15 % longer and
17 % stronger than wild type [
97
], but it is unclear how the bacterial cellulose
affects the structure and composition of the fiber SCW to change these properties.
Genetic Modification for Novel Fiber Traits
Along with genetic improvements to yield and conventional quality traits, attempts
have been made to genetically alter other fiber traits such as color and thermal
properties. The dyeability of cotton fibers is an important trait in the textile industry.
The process of dyeing cotton fibers is expensive and creates large volumes of toxic
waste, and, as a result, there has been an increased focus on naturally colored cotton
(mocha, brown, red, and green) by the organic cotton industry and environment-
minded consumers alike. Although only grown on a small-scale, colored cotton
represents a niche market. Genetic engineering of cotton to produce a greater
variety of colored fibers has received some attention in recent decades with a
primary focus on the two main colors used for mass-produced blue and black
denim. Genes responsible for melanin and indigo production were inserted into
cotton resulting in some color formation in the fibers [
98
]. While the color intensity
was not sufficient for commercial use, these attempts suggest that there is potential
for producing novel fibers through genetic modification.
The synthetic textile industry has produced many innovative fiber products,
including bicomponent fibers that contain a core polymer surrounded by a sheath
polymer that combines the properties of the two polymers in one fiber. Attempts at
replicating this innovation in cotton fiber have included the introduction of bacterial
genes for the production of an aliphatic polyester compound, polyhydroxybutyrate
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