THE TT10 GENE AFFECTS THE BROWING OF ARABIDOPSIS SEEDS
browning of Arabidopsis seeds depends on their flavonoid content. The
proanthocyanidins (PAs), also called condensed tannins, accumulate
specifically in the seed coat and give the mature seed its brown colour
after oxidation. The French scientists at INRA have studied the gene
that controls this process.
gene involved in controlling the browning process is known as TT10.
It has been discovered that a mutation of this particular gene results
in the absence of a polyphenol oxidase enzyme (laccase). The tt10
mutant seeds are yellow at maturity and accumulate more soluble PAs and
less flavonol dimers than the wild type.
Flavonoid biosynthesis produces two major end-products in Arabidopsis
thaliana seeds. These two end-products are PAs (i.e.
polymers of epicatechin units), and flavonols. These seeds
provide an excellent model for investigating flavonoid biosynthesis due
to the wide range of mutants that lack the ability to produce
flavonoids. The comparison of wild-type plants that produce flavonoids
with mutant plants that do not produce them, can reveal those genes that
are involved in flavonoid production.
Proanthocyanidins and flavonols are classes of flavonoids that have been
found in large amounts in fruits and plant-derived products. They are
formed as a result of plant metabolism. They play an important role in
plant defence against biotic and abiotic stresses, and are known to have
beneficial effects on human health. They have been shown to have
antioxidant activity that may out-perform that of vitamin C and vitamin
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