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Unravelling thegenetic blueprint ofwine yeastBorneman, A.R.; Forgan, A.H.; Chambers, P.J.; and Pretorius,I.S.The Australian Wine Research Institute, PO Box 197, GlenOsmond (Adelaide), South Australia 5064, AustraliaIn a world first, scientists at the Australian Wine ResearchInstitute have sequenced the wine yeast genome,characterising the ‘recipes of life’ that shapethis winemaker’s ‘friend’.Unlocking the secret to what makes wine yeast tickwill put winemakers in a stronger position to usescience to their advantage. This work paves the wayfor the development of new yeast strains, potentiallyleading to innovative solutions to tackle stuckfermentation and to create wines with desired alcohollevels and flavour profiles.Every four years, the Olympic Games inspire the worldwith spectacular performances and feats of endurance,speed and grace. We marvel at the athletic performanceof the competitors; most of us can only wonderhow these champions reach the standards theydo. What makes world record-breakers so profoundlydifferent to the rest of us? Are we not the same species,and therefore shouldn’t we all have the samepotential? Couldn’t we also win gold in swimming orrunning if we had the same training regimes, diet, lifestyle,etc.? The answer is no. Elite athletes are bornwith a potential that has ‘gold’ stamped all over it. Theyhave muscle-types, physique, physiology and aptitudethat, with training, can be honed for internationalsuccess. Unfortunately, most of us would require agreat deal more than honing to reach this elite level;until bionics is able to rebuild what we are born with,when it comes to athletics, most humans will have tosettle for amateur league or less (Figure 1(a)).Differences in performance of individuals of the samespecies are not peculiar to humans; in fact we see iteverywhere in nature. Take, for example, the humbleyeast that winemakers use to craft complex, deliciouswine from sweet, syrupy grape juice. Most wine yeastare the same species, Saccharomyces cere visiae, butnot all members of this group are able to producewine, and, among those that do, there is considerablevariation in how reliably and efficiently they work, andin the quality of the wine they produce.Seminario TécnicoCompuestos azufrados volátiles en vinosThis begs the question: What makes a wine yeast tick?What, in the inner workings of this elite athlete, enablesit to grow in such an inhospitable environment and delivergold medal wines when other S. cerevisiae strainsdon’t even leave the starting blocks? Research at theAustralian Wine Research Institute (AWRI) is beginningto unravel the mysteries of the variation across the S.cerevisiae species, and early results on what they tellus about wine yeast are tantalising.The variation in performance that we see across strainsof S. cerevisiae is inheritable; this means that it isgenetically determined. The starting point for characterisingthis variation, therefore, should focus on yeastgenetics.Fortunately, S. cerevisiae was the first organism of itstype to have its genetic make-up (its genome) sequenced,and this was done over ten years ago on a strain,known as S288c, chosen for its ‘laboratory friendly’characteristics (for more information on what genesand genomes are, see the breakout box). Scientistslove this yeast because it is very easy to work with, butit would not win any medals in the winemaking arena;in fact, it is probably not even up to amateur status.Nevertheless, if you want to find out what makes wineyeast so different from other S. cerevisiae strains, youhave to have something to compare it with, and S288cis a good starting point.Another strain of S. cerevisiae, YJM789, recently hadits genome sequenced. The genome of this yeast, anopportunistic pathogen isolated from the lungs of anAIDS patient, turned out to be quite different to thatS288c. Thus we had two different versions of S. cerevisiaeto compare a wine yeast against, and this is whatwe found.It turns out that our wine yeast is a little more differentto the two previously sequenced strains than they areto each other (Figure 2). About 0.6% of the letters ofthe wine yeast sequence are different to what is foundin the laboratory strain. This might seem like a smalldifference, but if you consider that genetic differencesbetween humans and chimpanzees amount to onlyabout 1-2%, it is really quite large.Perhaps of greater interest, however, is that thereare extra DNA sequences in the wine yeast; enoughto carry at least 27 genes that are not present in thetwo yeasts it was compared against. In fact, some ofthe sequences in this extra DNA do not resemble anythingfound in other species of Saccharomyces; theyappear to be more like genes found in very distantfungal relatives. We do not yet know how they gotinto the wine yeast genome, but we are curious tofind out whether or not they play a part in distinguishingwine yeast from other S. cerevisiae, particularly inthe winemaking stakes.Some of the wine yeast-specific genes encode proteinsthat are probably associated with the cell wall,Textos asociadosWine Industry Journal > Vol 23 No 5 > September /October 200873