Agriculture Reference
In-Depth Information
TableĀ 24.1 Alternative technologies for molecular plant breeding
Technology
Description
Comments
Small RNA (co-suppression, anti-sense,
RNAi)
An RNA-dependent
mechanism used primarily
to suppress specific gene
expression; occurs without
the insertion of a gene that
encodes a protein. DNA
encoding specific RNA is
inserted.
No novel protein is produced.
Cross-infection immunity
employed in traditional breeding
operates by the same or similar
mechanisms. Genetically
engineered virus resistant crops
have been approved.
In vivo mutagenesis
Reagents, enzymes, and
nucleic acid templates are
introduced into cells to
bring about site-specific
mutagenesis without the
introduction of new DNA.
Although the method employs in
vitro techniques no heterologous
DNA is introduced. Identical
DNA mutations could occur
spontaneously.
In vitro mutagenesis
A gene is cloned from an
organism and it is mutated
in vitro by site-directed
mutagenesis. The mutated
gene is reintroduced
into the parent organism
by transformation and
recombination.
Only mutated DNA isolated from
the same organism is introduced.
Identical DNA mutations could
occur spontaneously. Can also be
used to modify gene expression by
mutating regulatory elements.
Modification of transcription factors
Transcription factors
expression can be altered
by manipulation of the TF
promoter; alternative TFs
can be introduced.
No new protein is produced
or closely related proteins are
produced. The level of protein
expression is very low. Evidence
shows that traditional breeding
can modify or introduce novel TFs.
Cis -genic and intra-genic
transformation
Genes from other varieties
of the same species, or
closely related sexually
compatible species are
introduced using in vitro
transformation techniques.
Allows introduction of
iso-genes.
Genes are exchanged between
varieties. Homologous DNA
found in other varieties of the
same species is introduced.
Cross-breeding can produce the
similar results.
Transient expression
Genes or gene products are
introduced into the plant.
Novel DNA is not inserted
permanently into the
genome. Genes can also be
inserted and subsequently
excised.
No novel DNA is present in edible
parts of the organism. Novel
characteristics typically depend on
transient effects.
Grafting
Conventionally bred plants
are grafted into transgenic
rootstock. Useful for trees.
No novel DNA, protein, or
metabolites need be present in
the edible portions of the plant.
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