Wetenschappers claimen nieuwe druivenrassen te make

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http://www.wijnwijs.eu/index.php/wijnnie...e-wijnbouw

In het Nieuw Zeelandse Christchurch is een groep wetenschappers aan de Lincoln University bezig een ‘revolutie’ te veroorzaken in de wijnbouw. Dat laat dr.Chris Winefield van deze universiteit vandaag weten. Het gaat om genetisch onderzoek waaruit nieuwe druiven-variëteiten en wijnstijlen zullen resulteren, zo claimt de onderzoekersgroep. De nieuwste vondst: transposons. Als die in de druif worden geactiveerd, gebeuren er wonderlijke dingen.

“The global wine industry may be on the cusp of a revolution, thanks to pioneering genetic research conducted by scientists at Lincoln University and Plant & Food Research that not only has ramifications for controlling disease and increasing productivity, but will quite likely mean completely new varieties of grapes and styles of wine.

The research project initially commenced to fill a knowledge gap in the identification and function of the genes that underpin the key characteristics of grapevines. The goal was to bed down a research framework, such as those used by researchers with other plant species, to establish a knowledge base for the study of gene behaviour and the critical processes of grape production.

As the research developed, however, new opportunities became apparent, and a greater emphasis was placed on investigating the potential for manufacturing and encouraging the expression of genetic elements within grapevines which may, in turn, come with commercial benefits.

Mobile DNA

At the heart of the research are transposons: naturally occurring, mobile DNA sequences that have the ability to replicate and insert themselves into new positions within the same or another chromosome.

All living organisms have transposons and often in very high quantities. Up to 40 percent of the grape genome is made up of transposons with most inter-clonal diversity within grapevines caused by them. Yet, while most transposon expression within a grape variety is unwelcome or harmful, they usually remain ‘silenced’ through the plant’s own internal system which looks to prevent new mutations.

There are numerous cases, however, where transposons can be activated; under certain stress conditions, for instance, such as UV exposure, temperature shocks, or exposure to certain microorganisms such as bacteria or fungi. As such, the researchers explored how to activate and identify transposon expression within grapevines with a view to producing a population of plants in which each plant contained a number of new insertions.

“Through our five year project with Plant & Food Research we have now proven this to be possible and are looking to extend this work to produce populations of grapevines in which every gene in the genome contains a transposon insertion,” says Dr Chris Winefield , project team leader and Senior Lecturer in Plant Molecular Biology at Lincoln University.

Conditions

“In a sense we’re looking to create stress conditions so as to ‘hyper-activate’ the genome, thereby creating conditions conducive for dense, multiple transposon insertions,” says Dr Winefield. “We can then search the individual plants for transposon insertions in their genes and subsequently assess to what extent the transposon has disrupted the gene and what impact this will have on the plant.

“From there, we can assess which plants we could be interested in from a commercial perspective; for instance, for reasons such as disease tolerance, sustainable production, or a capacity to produce an interesting new variety of wine.”

In order to activate the transposons, the researchers worked with plant tissue cultures from grapevines. After subjecting these cultures to a range of stress treatments, the plants were regenerated from the cultures and new transposons insertions identified using bioinformatics.

The work of Lincoln University PhD candidate Darrell Lizamore was crucial in developing a means for identifying and measuring these genetic mutations: work which earned him the prestigious David Jackson prize in 2013, awarded for research showing rigour, innovation and the potential for beneficial changes to the wine industry.

The problem of finding a method for identifying new transposon insertions was made all the more difficult by the large ‘background’ of ancient transposons in the grapevine genome, and the fact that new transposon insertions might only make up 0.2% of the entire transposon compliment.

To overcome this, transposons were ‘tagged’ using a fluorescent dye, after which the tagged DNA was sorted using a capillary DNA sequencer. This allowed transposons to be grouped according to their particular type and position within the grapevine’s DNA.

The systematic, multi-experimentation approach to overcome the problem of transposon identification, as well as other problems, such as the development of treatment protocols capable of activating specific transposons, has meant a considerable body of information is now available to the wine industry. This information is of particular importance as it involves sequencing approaches across the entire grape genome.

Now that the ‘hard yards’ are done, this sequencing and resequencing information is openly available to researchers who wish to identify individual plants with interesting new mutations with an eye for replicating them further. Resequencing is a process whereby the complete set of genes making up a genome are catalogued and usually compared to the sequence (or catalogue) of genes from an original reference genome.

New wines

“The upshot of this work is that we are now in a position to encourage, identify and replicate mobile genetic elements so as to increase genetic diversity in grapevines,” says Dr Winefield. “This approach is non-GE and uses the same processes that underpin the formation of common bud-sports in grapes and other similar species.

“As far as the wine industry itself is concerned, we now have the means to generate new clones of existing varietals and the experimental framework to explore the production of completely new wines. This is very exciting and significant.”

The possibility of New Zealand leading the world in the production of completely new varieties has exciting commercial implications for a competitive industry where differentiation is important and where grape types are used to market products as a marker of style and quality.

The ground-breaking research also stands to contribute significantly to the international research community by having established a robust experimental research platform and database for other researchers to build on and leverage off for their own projects. Likewise, the research methodology and technology employed has considerable implications for other plant species important to New Zealand’s primary industries.

Plant & Food Research has played a pivotal role in the project. As a Crown Research Institute, it is responsible for delivering research and development to support a range of primary sector industries, including wine, and has a long history of working closely with these industry partners.

“We’re very pleased to be working in partnership with Lincoln University on this project. The research really does have the potential to create a range of new opportunities for the New Zealand wine industry,” says Plant & Food Research Chief Operating Officer, Dr Bruce Campbell.

As well as Dr Chris Winefield and PhD candidate Darrell Lizamore, the research team is made up of Dr Ross Bicknell at Plant & Food Research, who coordinates the Crown Research Institute’s particular involvement in the project and has a background in grape genetic improvement; Dr Susan Thompson at Plant & Food Research, who has been instrumental with sequencing analysis and informatics development; Joshua Philips, lab manager and research associate for the project; and Tirthanker Ghosh, a Lincoln University PhD candidate who will be expanding on Darrell’s work to research a larger plant population and further examine the impact of new transposon insertions.