RNASeq analysis of drought-stressed guayule reveals the role of gene transcription for modulating rubber, resin, and carbohydrate synthesis

Authors: Dong, Chen; Ponciano, Grisel; Huo, Naxin; Gu, Yong; ILUT, DANIEL - Cornell University; McMahan, Colleen

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2021
Publication Date: 11/3/2021
Citation: Dong, C., Ponciano, G.P., Huo, N., Gu, Y.Q., Ilut, D., McMahan, C.M. 2021. RNASeq analysis of drought-stressed guayule reveals the role of gene transcription for modulating rubber, resin, and carbohydrate synthesis. Scientific Reports. 11. Article 21610. https://doi.org/10.1038/s41598-021-01026-7.
DOI: https://doi.org/10.1038/s41598-021-01026-7

Interpretive Summary: Successful cultivation of guayule as an industrial crop relies on improved germplasm and agronomic practices. In this work, studying guayule at the RNA level provided new insight on how and when plants produce natural rubber, resin, and carbohydrate, all three of which are valuable carbon-based products. Guayule produces more rubber when it is under drought stress, but expression of genes (RNA) for the rubber pathway is mostly down-regulated. At the same time, an important gene related to conversion of carbohydrates to sugars, is up-regulated, suggesting the sugars provide the carbon for rubber production. This study helps to identify strategies for crop improvement, but in addition, informs field practices. Results suggests that field irrigation practices might be calibrated to enable tunable accumulation of rubber, resin and carbohydrate in guayule.

Technical Abstract: The drought-adapted shrub guayule (Parthenium argentatum) produces rubber, a natural product of major commercial importance, and two co-products with potential industrial use: terpene resin and the carbohydrate fructan. The rubber content of guayule plants subjected to water stress is higher compared to that of well-irrigated plants, a fact consistently reported in guayule field evaluations. To better understand how drought influences rubber biosynthesis at the molecular level, a comprehensive transcriptome database was built from drought-stressed guayule stem tissues using de novo RNA-seq and genome-guided assembly, followed by annotation and expression analysis. Despite having higher rubber content, most rubber biosynthesis related genes were down-regulated in drought-stressed guayule, compared to well-irrigated plants, suggesting post-transcriptional effects may regulate drought-induced rubber accumulation. On the other hand, terpene resin biosynthesis genes were unevenly affected by water stress, implying unique environmental influences over transcriptional control of different terpene compounds or classes. Finally, drought induced expression of fructan catabolism genes in guayule and significantly suppressed these fructan biosynthesis genes. It appears then, that in guayule cultivation, irrigation levels might be calibrated in such a regime to enable tunable accumulation of rubber, resin and fructan.