Location: Bioproducts Research
Project Number: 2030-21410-021-15-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2017
End Date: Aug 31, 2019
The overall goal of this integrated SBAR project is to maintain and expand the rural bioeconomy of arid regions in the US by combining research, extension and outreach. The hypothesis is that further feedstock development and production optimization of guayule and guar will enable the Southwest U.S. to expand our base for the commodity, biofuel, and high-value product markets. The objective of the ARS Scientist components is to apply molecular approaches to create guayule plants with reduced or eliminated flowering in mature plants, since flower reduction in field plots has shown a positive impact on rubber yield.
We propose to apply molecular approaches to create guayule plants with reduced or eliminated flowering in mature plants. We will identify native guayule gene candidates for controlling flowering in guayule, and perform gene expression analysis of the top candidates. DNA sequencing of a diploid guayule has recently been completed (Valdes-Franco, et al. in preparation) and we will perform of standard bioinformatic analysis of the genome and associated transcriptome to better understand the structure and expression of candidate genes. Quantitative PCR analysis of gene expression will be performed for greenhouse and field plants, targeting genes known to be related to flowering in plants. We have recently sequenced the transcriptome of two sets of irrigation trial field plants (Hunsaker et al. unpublished), one showing normal growth and the other showing early flowering due to drought stress. These data will also inform our understanding of molecular control of flowering in guayule. From these studies we will select the best strategies (downregulation, overexpression, or both). Vectors will be prepared for guayule plant transformation, using backbone plasmids known in our lab to be successful in guayule transformation (Dong et al. 2013). We will transform plants using standard molecular techniques for preparation of plant transformation vectors and Agrobacterium-mediated transformation. Phenotypes will be evaluated: PCR to confirm transformation, q-PCR for gene expression, natural rubber and resin microanalysis by extraction, plant morphology and flowering in growth chamber and greenhouse conditions. We will use tools well-established in the USDA-ARS laboratories. For Year 2: In this time period we will transform guayule to downregulate the target genes. Constructs will be prepared for the target genes SEPATALLA3 and FLOWERING LOCUS T, both of which have been cloned. Transformations will be performed for these two genes plus the original APETALA1. Our goal is to obtain 6 independent lines with confirmed downregulation of the genes.