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Title: The role of the small rubber particle protein in determining rubber yields and polymer length in Russian dandelion

item COLLINS SILVA, JILLIAN - University Of Nevada
item NURAL, AISE - University Of Nevada
item SCOTT, DEBORAH - University Of Nevada
item HATHWAIK, UPUL - University Of Nevada
item WOOSLEY, REBEKAH - University Of Nevada
item SCHEGG, KATHLEEN - University Of Nevada
item McMahan, Colleen
item Whalen, Maureen
item CORNISH, KATRINA - Yulex Corporation
item SHINTANI, DAVID - University Of Nevada

Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2012
Publication Date: 5/19/2012
Citation: Collins Silva, J., Nural, A.T., Scott, D.J., Hathwaik, U., Woosley, R., Schegg, K., Mcmahan, C.M., Whalen, M.C., Cornish, K., Shintani, D.K. 2012. The role of the small rubber particle protein in determining rubber yields and polymer length in Russian dandelion. Phytochemistry. 79:46-56.

Interpretive Summary: Russian dandelion is under development as a new crop in the United States for production of natural rubber and inulin, a storage carbohydrate co-product. Sustainability of domestic natural rubber-producing crops like Russian dandelion would be enhanced by improved yield, potentially via biotechnology. While much of the biochemistry of natural rubber production is known, key elements are missing. One of those is a better understanding of the role of rubber particle proteins like SRPP, the small rubber particle protein, first identified in Hevea in 1999. SRPP proteins or homologs exist in many rubber-producing plants and are found tightly associated with rubber particles. This study explores the role of SRPP in Russian dandelion. Results indicate that the SRPP does play a role in rubber biosynthesis in Russian dandelion.

Technical Abstract: Several proteins have been identified and implicated in natural rubber biosynthesis, one of which, the small rubber particle protein (SRPP), was originally identified in Hevea brasiliensis as an abundant protein associated with cytosolic vesicles known as rubber particles. While previous in vitro studies suggest that SRPP plays a role in rubber biosynthesis, in vivo evidence is lacking to support this hypothesis. To address this issue, a transgene approach was taken in Taraxacum kok-saghyz (Russian dandelion or Tk) to determine if altered SRPP levels would influence rubber biosynthesis. Three dandelion SRPPs were found to be highly expressed on dandelion rubber particles. The most abundant particle associated SRPP, TkSRPP3, showed temporal and spatial patterns of expression consistent with patterns of rubber accumulation in dandelion. To confirm its role in rubber biosynthesis, TkSRPP3 expression was altered in Russian dandelion using over-expression and RNAi methods. While TkSRPP3 over-expressing lines had slightly higher levels of rubber in their roots, relative to controls, TkSRPP3 RNAi lines showed significant decreases in root rubber content and produced dramatically lower molecular weight rubber than control lines. Not only do results here provide in vivo evidence of SRPP affecting the amount of rubber in dandelion root, but they also suggest a function in regulating the molecular weight of the cis-1,4-polyisoprene polymer.