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In February 2004, Genome Canada and UBC announced a new $6.2 million collaborative research project, “GrapeGen”, between scientists in BC and Spain aimed at understanding genomic mechanisms controlling berry ripening and quality in wine and table grapes. Collaborators on the GrapeGen project in Canada included Dr. Joerg Bohlmann, UBC Michael Smith Laboratories; Drs. Marco Marra, Steven Jones, Rob Holt, Michael Smith Genome Sciences Centre, BC Cancer Agency, Vancouver, BC; Dr. Christoph Borchers, UVic-Genome BC Proteomics Centre, Victoria, BC. The Spanish leader collaborating on the project was Dr. Jose Miguel Martinez Zapater, el Centro Nacional de Biotecnologia, Madrid, and his team consisted of 5 additional PIs throughout Spain. This 3.5 year project was successful in establishing a diverse technology platform in the UBC Wine Research Centre and in BC, which we are now exploiting to study hormonal regulatory networks controlling ripening initiation as well as the metabolism of malic acid and terpenoid compounds in Cabernet Sauvignon, Gewurztraminer, and Pinot Noir grape berries. Highlights of technology development achievements of the GrapeGen project include:
- submission of over 77,000 ESTs to the public domain including over 2,000 new sequences for Vitis vinifera
- production of a new proprietary Affymetrix microarray for Vitis vinifera representing approximately two thirds of the predicted grapevine transcriptome
- design of EST clustering and processing scripts for annotations of proteomics data
- development and implementation of a quantitative proteomics technique, iTRAQ
- development and implementation of an enzymatic-cleavage based protocol for quantitation of potentially volatile compounds in grape berries
- implementation of genetic transformation and regeneration protocols for in vitro grape callus cultures
We are currently finalizing a new international collaboration that will broaden objectives to include wine yeast genomics, as well as increase the focus on grapevine physiology, chiefly the interaction of nitrogen application, carbon allocation, and cluster shading on gene expression and compositional chemistry in berries. An award announcement and project launch are anticipated soon - check back for details at a later date.
Grapes (Vitis spp.) are the most economically important fruit species in the world. Nineteen million acres worldwide are planted in vineyards for wine, juice, and table grape production. Canada's economic interest in grapes lies in the production of high quality wines. Although Canada is one of the youngest wine-producing regions in the world, the wine industry in Canada has grown rapidly over the most recent 10 years, primarily in Ontario and British Columbia, as well as in Quebec and Nova Scotia. In addition to producing the finest icewines in the world, Canada has recently gained acclaim as a producer of high quality, award-winning wines, crafted from classic French and German V. vinifera varietals. In BC alone, the value of quality-assured (VQA) wines increased from nearly 7 million dollars in 1992 to over 150 million dollars in 2007, according to the BC Wine Institute. The Canadian wine industry projects continued growth over the next ten years.
Given the high economic value of grape production in numerous countries worldwide,  increasing investments have recently been directed towards better understanding molecular mechanisms underlying ripening and berry flavour traits for improvement of the grape industries. Fruit quality in any vineyard can vary from year to year. This inconsistency can be largely attributed to changes in microclimate and viticulture management practices. The genetic determinants of grape flowering, ripening initiation, and flavour are largely unknown. Furthermore, how external factors interact at the genomic level to cause differences in the timing and synchrony of ripening initiation within clusters, as well as the balance of flavour components at harvest, is not well understood. Essentially, the berry constitutes a ‘black box’ to growers - what is happening at the molecular level in individual berries and berry clusters as each season progresses? A major goal of our grape omics research is to take a "systems biology" approach to discover molecular components associated with key stages of berry development and investigate how these signaling networks and metabolic pathways are globally modified in response to environmental conditions commonly encountered in the vineyard. We expect that these large-scale analyses will allow us to identify gene and protein candidates specifically associated with ripening and quality in berries, to formulate hypotheses, and then test these in a more focused manner through functional assays and molecular interaction studies. The recent publications by French and Italian groups of two draft genome sequences in Pinot Noir genotypes is a major breakthrough that we expect will accelerate grapevine omics research worldwide. We anticipate that an advanced understanding of grape berry omics will not only increase our basic understanding of several aspects of fruit physiology, but also provide the resources to develop molecular-based tools to help growers fine-tune their viticultural practices from season to season and better achieve consistent, high berry quality for wine production in Canada.
Berry development follows a biphasic growth pattern. Following fruit set in the first phase, there is an initial burst of cell division and expansion in the mesocarp and seed lasting around 6 weeks. This is accompanied by accumulation and storage of organic acids, chiefly malate and tartrate, in mesocarp cell vacuoles. This is followed by a lag period in which expansion slows for about 2 weeks and seed maturation is completed. Finally, the second phase of berry ripening is rapidly initiated and is marked in red cultivars by accumulation of pigments (anthocyanins), biosynthesis of important flavour and aroma compounds (e.g. terpenoid, norisoprenoid, and ester compounds), down-regulation of glycolysis coupled with sucrose accumulation, and metabolism of malate as the major carbon source for respiration. The metabolism of malate is important for controlling final acid levels in the grape juice at harvest. The cooler climates such as Canada and Germany tend to cause higher acid levels at harvest whereas in warmer climates such as that in a large percentage of Spanish and Australian vineyards, malate is metabolized at a higher rate and grape juice tends to have low acidity. Millions of dollars are spent annually to correct both extremes worldwide.
Control of the timing of ripening, berry size and colouration, acidity, and the relative assortment of volatile and potentially volatile compounds important for flavour in table and wine grape cultivars are major concerns for viticulturalists. Grape ripening is non-climacteric. While it is well-established in climacteric fruits such as tomato that the gaseous hormone, ethylene, is a key trigger for ripening, in non-climacteric fruits such as grape, it remains to be discovered how ripening is triggered. The tight and rapid change in a wide variety of transport and metabolic events suggests coordinate regulation and cross-talk amongst signaling pathways feeding into these metabolic processes. Thus, key targets for our gene and protein discovery programs in grapevine are candidate molecules involved in intercellular and intracellular signaling. Enzymes involved in the biosynthesis and storage of acids and glycone terpenoid compounds are also being targeted.
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