Location: Bioproducts ResearchTitle: Transcriptome and gene expression analysis in cold-acclimated guayule (Parthenium argentatum)rubber-producing tissue Author
Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2012
Publication Date: 5/9/2012
Citation: Ponciano, G.P., Mcmahan, C.M., Wengshuang, X., Lazo, G.R., Coffelt, T.A., Collins-Silva, J., Nural-Taban, A., Golley, M., Shintani, D.K., Whalen, M.C. (2012). Transcriptome and gene expression analysis in cold-acclimated guayule (Parthenium argentatum)rubber-producing tissue. Phytochemistry. 79:57-66. Interpretive Summary: Guayule is a woody desert shrub under development as a domestic source of natural rubber for cultivation on semi-arid farmlands. Genetic modification of guayule for increased rubber yields could significantly contribute to economic sustainability of this new crop, but until now little information has been available on the genetic makeup of the plant. This study represents the first published analysis of genes expression in guayule. Since guayule is known to produce more rubber in the winter, after exposure to low temperatures, we focused first on genes expressed in rubber-producing bark tissue collected during the winter. Surprisingly, gene expression did not generally correlate to increased rubber biosynthesis activity, strongly suggesting that other factors are important. Those factors might include time to build up a critical concentration of protein, or plant-induced chemical modification to those proteins. A better understanding of the biochemical and genetic control of rubber production may lead to more success in breeding or genetic engineering of increased yield.
Technical Abstract: Natural rubber biosynthesis in guayule (Parthenium argentatum) is associated with moderately cold night temperatures. To begin to dissect the molecular events triggered by cold temperatures that govern rubber synthesis induction in guayule, the transcriptome of bark tissue, where rubber is produced, was investigated. A total of 11,748 quality expressed sequence tags (ESTs) were obtained. The vast majority of ESTs encoded proteins that are similar to stress-related proteins, whereas those encoding rubber iosynthesis-related proteins comprised just over one percent of the ESTs. Sequence information derived from the ESTs was used to design primers for quantitative analysis of the expression of genes that encode selected enzymes and proteins with potential impact on rubber biosynthesis in field-grown guayule plants, including 3-hydroxy-3-methylglutaryl-CoA synthase, 3-hydroxy-3-methylglutaryl-CoA reductase, farnesyl pyrophosphate synthase, squalene synthase, small rubber particle protein, allene oxide synthase, and cis-prenyl transferase. Gene expression was studied for field-grown plants during the normal course of seasonal variation in temperature (monthly average maximum 41.7 'C to minimum 0 'C, from November 2005 through March 2007) and rubber transferase enzymatic activity was also evaluated. Levels of gene expression did not correlate with air temperatures nor with rubber transferase activity. Interestingly, a sudden increase in night temperature 10-12 days before harvest significantly correlated with the highest CPT gene expression level.