Dr. Laurent Deluc, Associate Professor, Dept. of Horticulture, OSU Oregon Wine Research Institute

As part of the research project studying the role of the regulatory protein Auxin-Response Factor 4, namely ARF4, on the ripening initiation of grape berries, our group has lately invested time and research efforts in promoting the microvine system at OSU, which was developed by our Australian partner Dr. Mark Thomas at the Commonwealth Scientific and Industrial Research Organization (CSIRO) (Chaïb et al. 2010). In early May, we received the first plant materials from Australia (see Figure 1 & 2), which includes in vitro material from white and red-grape varieties. One question that we are often asked about the microvine system is “what is the microvine system and why is it important to research?” If recent advances in sequencing technologies and genomic tools are very helpful to build new hypotheses on complex molecular processes, such hypotheses still need to be validated in planta in order to prove the concept. When one gene from genomic data has been identified as potential link with a trait of interest (fruit quality, disease resistance, stress tolerance), one way to prove the relationship between the genetic marker and the trait of interest is to perform “genetic engineering” or molecular breeding. To do so, this approach requires the use of a reliable model system that must combine several advantages that include small space requirements for growth, short generation time (constant flowering trait), tractable system for genetic engineering (genetic transformation), and small-size genome. The microvine system offers all of these advantages.

Dr. Satyanarayana Gouthu, Research Associate in the Deluc lab, is currently visiting Dr. Mark Thomas’s lab at the CSIRO in Australia to receive the necessary training for the different steps related to microvine propagation and genetic transformation. From my interaction with Dr. Gouthu, it is clear to me that he is learning a lot about microvine, which is essential for him to “master” when he eventually initiates the genetic engineering work at OSU. Meanwhile, another aspect of his research project is also in its final phase. By the end of the summer, we hope to identify a series of potential “interactors” with ARF4. This information is necessary to understand how a protein (ARF4) is regulated and what ARF4 interacts with during the process of berry ripening? We also made significant progress in terms of adapting a new method called Atmospheric Pressure Gas Chromatography Mass Spectrometry (APGC-MS) for metabolite identification in grape berries, in collaboration with the OSU Mass Spectrometry Center. Our colleague from the center has built a database containing around 75 individual analytes belonging to different classes of metabolites (organic acids, amino acids, sugar-related compounds, and pigment- related compounds). Our goal is not only to use this database for routine metabolite analyses in our lab, but also over time to improve the depth of the database by adding new metabolites. We are currently running samples from another experiment with promising results. We are very excited using this new analytical method for our current research project on ARF4 and future research projects as well.

By using the microvine, we expect to connect the function of proteins to important traits for grapevine production. Our goal is to specifically connect the timing of ripening initiation to the protein ARF4. This information could be useful by providing the industry with a potential genetic marker associated with véraison that could serve be used to validate new practices in the field, and to identify new or existing cultivars/clones for advanced or delayed ripening more amenable to local changes in the environment due to climate change. We hope to collaborate with OWRI, OSU and other external partners in pursuit of our research objectives.

Figure 1. Microvine embryonic cells of white grape variety

 

Figure 2. Microvine plantlet of red grape variety

Literature cited:

Chaïb J, Torregrosa L, Mackenzie D, Corena P, Bouquet A, Thomas MR. 2010. The grape microvine- a model system for rapid forward and reverse genetics of grapevines. Plant J. 62(6):1083-92. doi: 10.1111/j.1365-313X.2010.04219.x

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