Agriculture Reference
In-Depth Information
wines, because I fi nd Pigato wines recognizably
different from Vermentinos most of the time,
and from Favorita even more often. Pigato
and Vermentino in Liguria often share the
same vineyard parcel, and yet, to my taste, their
wines do smell and taste suffi ciently different
to warrant at least raising an eyebrow or two.
Angelo Negro, one of the best producers of
Roero in Piedmont, told me recently how
years ago he planted both Pigato and Favorita
side by side in a vineyard (because a university
expert had told him the varieties were identi-
cal), but that both the grapevines and the wines
made from them couldn't have turned out more
different. Now there's food (er, wine) for
thought.
Given how complicated the world of Italian
native and traditional grapes is, with myriad
slightly-different looking grapes that are said to
be “genetically similar,” this becomes a very
important question. When we say—or are
told—that varieties are “genetically identical,”
do we know exactly what that means? This is
not at all a moot point, since we know that the
different phenotype expressions of biotypes do
have a genetic background: for example, analy-
sis of up to one hundred DNA markers (which
in practice is never done) showed that a few
genetic variations can be observed among
clones of
Pinot,
as with Chardonnay (Riaz, Gar-
rison, Dangl, Boursiquot, and Meredith 2002).
I don't think anyone knows for sure, but per-
haps sequencing out the entire genome of the
Cataratto
s, or of Pigato/Vermentino/Favorita
might show that genetic differences between
them are more widespread than we believe
them to be.
In fact, even when DNA looks totally identi-
cal, it may function, or be made to function, in
completely different manners, leading to com-
pletely different results. DNA is far more com-
plex than scientists initially believed: in fact,
over the last thirty years it has become increas-
ingly apparent that we still don't know enough
about the nucleic acids (both DNA and RNA)
and their many intricate functions and interre-
lations. At the present state of genetic knowl-
edge, when DNA profi ling shows that two
grapevines have the same microsatellite repeat
sequences, scientists conclude that the two
grapevines are identical. I wonder. For exam-
ple, we have learned that those portions of DNA
that supposedly don't code for anything,
defi ned by scientists as “junk DNA” or “non-
sense DNA,” which DNA profi ling using the
microsatellite technique relies upon for its
results, actually are not passive at all. They may
all look the same, but they don't necessarily
work the same way. Hence, it cannot be
excluded that the end result of their activity
may lead to altogether different results, in this
case, what ultimately are distinct grape varie-
ties. For example, even portions of junk DNA
are transcribed (copied) into RNA molecules
with different functions. RNA does a lot more
than act only as a messenger and a translator.
Rather it exerts an infl uence on DNA at many
levels, regulating gene activity and expression:
it can do so not just during transcription and
translation, but at post-transcriptional and post-
translational levels as well. In fact, while we
tend to think of our world as governed by DNA,
RNA is just as important, and perhaps even
more. Besides the well-known mRNA and
tRNA, other RNA molecules have been recently
described, for example mRNA molecules that,
despite their name, do not seem to transport
any specifi c message. All these RNA molecules
can exert control over what the DNA ultimately
does, but they are themselves subject to various
control mechanisms. How and why these RNA
molecules interact with DNA is the subject of
research studies in laboratories and universi-
ties all over the world.
Clearly, the genome is far more complex than
we once thought: for instance, the present defi -
nition of
gene
as that portion of DNA which
codes for a protein is undoubtedly limited. Using
that defi nition, for example, only 2 percent of
human DNA is made up of genes, and that's just
not possible, for there are many more portions of
DNA that are quasi-genes, which either do
something or are made to do something by
interaction with appropriate RNA molecules of
