replicate it in commercial cultivars of crop species,”
were developed to join things, or separate them - the
same is true of most of the power tools in a modern garage,” Hellens said. © freeimages.com/profile/tvvoodoo
Hellens’ own research in recent times has focused on the biosynthesis pathways in fruit that produce flavonoid compounds and vitamin C, both potent antioxidants with potential health benefits for humans. But his team’s work to increase vitamin C concentrations in fruit has a broader goal: dietary vitamin C is crucial to the body’s ability to absorb
the emerging tools of molecular genetics are very good at making precise cuts, and excising DNA sequences with precision. “But we’re not particularly good at sticking things back together again. It’s particularly true for
iron. “Increasing vitamin C in plants doesn’t affect the concentration of iron in the plant, but it does enhance
involved, we have the tantalising prospect of elevating
the body’s ability to absorb iron,” Hellens said.
vitamin C concentrations in other plants in the human
“Around 1.6 billion people around the globe
“Most of the things we do involve breaking or cutting DNA, and sticking it together again. Some of
diet,” Hellens said.
plant DNA. “I believe that, in the future, we will develop a better understanding of the mechanisms involved in
are chronically anaemic because they don’t absorb
“We could prevent anaemia and keep people
enough iron from their diet. Elevating vitamin C
alive and healthy by editing the genomes of important
“When conventional plant breeders introduce
concentrations in the diet could help correct iron-
commodity crops to replicate naturally occurring alleles
a gene into a crop, and back-cross, they are doing
in high-vitamin C species like kiwifruit, Kakadu plum,
basically the same thing - double-strand breaks are
Amazonian fruits like acerola and camu camu, or the
required for the recombination events that lead
Indian gooseberry,” Hellens said.
to the hybrid progeny, so you’re further blurring
Hellens says his team’s research has determined not only how vitamin C is made in fruit, but how its production is regulated.
Targeted methylation or demethylation of genes, and
the differences between molecular genetics and
Hellens says his team’s studies of kiwifruit, which
homologous recombination, are among future tools for
has 50 times the vitamin C of oranges, and Australia’s
manipulating the activity of genes in situ in crop plants.
Hellens says that for virtually every trait of
Kakadu plum, Terminalia ferdinandiana, which has the
Hellens says it is already possible to demethylate
importance in crop plants, there will be a pool of
highest concentration of vitamin C of any fruit in the
genes, but selectively silencing genes by target
genetic diversity within the crop and its wild relatives
world - 200 times more than oranges - have revealed
methylation is not yet feasible - however, it may be
to improve it. Rather than install the allele of interest,
that a single nucleotide substitution in the regulatory
possible, by demethylating repressor genes, to activate
the preferred approach will be to use homologous
region of an enzyme involved in vitamin C biosynthesis
dormant downstream genes, to achieve gain-of-
recombination to ‘overwrite’ the gene in situ in
changes one peptide in the enzyme, resulting in a very
function traits, Hellens said.
the crop plant - the trait might affect yield, disease
large increase in vitamin C concentration.
Modifying genes in situ by homologous
resistance, drought tolerance, dwarfing - “We know
Vitamin C from fruits is more readily absorbed by
recombination has been used for years to create
that lots of alleles exist in the wild, and we can use
the human gut than vitamin C in the form of ascorbic
transgenic animals, but researchers have yet to find a
them,” he said.
acid tablets, sold by chemists.
way of making it work reliably in plants.
“Many traits are multigenic, but I don’t believe
“Although we’re only at the preliminary stages of
“I once drew an analogy between modern
the project, because we now understand the mechanism
molecular genetics and toolmaking: all primitive tools
42 | LAB+LIFE SCIENTIST - October 2014
any trait is so complex that it is not amenable to molecular dissection.
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