Location: Bioproducts Research
Project Number: 2030-30600-003-000-D
Project Type: In-House Appropriated
Start Date: Apr 13, 2025
End Date: Apr 12, 2030
Objective:
Obj 1: Advance the mechanistic understanding of stress-induced rubber biosynthesis in plants: enzyme complex components and molecular regulation.
Sub-obj 1A: Identify components that constitute the Rubber Transferase biosynthetic complex.
Sub-obj 1B: Conduct differential gene expression analysis of cold-induced guayule tissues to identify genes involved in rubber biosynthesis.
Obj 2: Develop guayule lines with increased rubber yield.
Sub-obj 2A: Develop CRISPR technologies for modifying functional traits in guayule.
Sub-obj 2B: Assess a guayule variant derived from AZ-2, an industrial standard germplasm, for increased rubber production.
Sub-obj 2C: Over-express transcription factors in guayule to develop a climate-resilient guayule crop and ensure higher and more consistent NR production.
Sub-obj 2D: Improve methods for plant tissue phenotyping.
Obj 3: Develop biobased antidegradants to replace 6PPD for stabilization of natural rubber: reaction mechanisms and green chemistry.
Subobj 3A: Develop, assess, and analyze potential 6PPD alternatives.
Sub-obj 3B: Develop an improved understanding of antiozonant performance and transformation.
Obj 4: Advance biodegradable natural rubber compounds using agricultural feedstocks.
Sub-obj 4A: Expand the use of heat-treated agricultural residues as bio-based reinforcing fillers in natural rubber compounds.
Sub-obj 4B: Evaluate and develop methods for natural rubber biodegradation.
Approach:
In Obj 1: Advance the understanding of rubber biosynthesis, we will 1A Identify
components of the Rubber Transferase (RuT) biosynthetic complex. Using guayule
genomic data under development in this project, machine learning based structural
modeling, and high-res microscopy, models of the essential rubber particle (RP)
components (proteins, lipids, rubber) will be developed. We will assemble in vitro RPs from recombinant RuT components and vary biochemical factors to optimize NR synthesis. In 1B we will use new guayule genomes for differential gene expression analysis of cold-induced tissues to identify genes and control factors involved in NR biosynthesis. This will allow a detailed investigation of the genetic x environment interactions in the context of NR biosynthesis by deep mining of transcription factors, regulatory elements and pathway genes, with weighted gene co-expression network analyses for field and lab plants exposed to cold. In Obj 2: Develop lines with increased yield, we will 2A develop CRISPR technologies for guayule. We will target the Tiller Angle Control (TAC1) architecture gene conducive to high NR yield. A knockout of guayule TAC1 gene will promote more vertical branching to increase plant density and NR production in the field. Leaf shading is expected to be reduced thereby enhancing photosynthetic activity and increasing biomass, two traits conducive to increased NR yield. In 2B we will assess a new guayule variant, AZ-2D, which grew faster and taller than AZ-2 seedlings and produced fewer flowers in lab studies. We will evaluate AZ-2D for NR production, plant architecture, biomass, and tolerance to environmental stress. In 2C we will overexpress PaCBF4 and other cold-inducible transcription factors in guayule targeting higher NR production. Gene expression studies will be used for molecular characterization of cold-induced signaling pathways. Finally, in 2D we will improve methods for tissue phenotyping for guayule and rubber dandelion. We will improve and standardize methods for more accurate and efficient measurement of
rubber, resin, carbohydrates, and isoprenoid pathway metabolites. In Ob 3: Develop biobased antidegradants, we will 3A synthesize, characterize, and screen novel chemistries for use as antiozonants. We will use green chemistry principles and raw materials from biobased sources to engineer both antidegradant function and safety. In collaboration with industrial and interagency partners, candidate molecules will be screened for rubber protection and aquatic toxicity. In 3B we will develop an improved molecular understanding of antiozonant performance, to better predict rubber compound protection and generation of transformation products. Finally, in Obj 4 Advance biodegradable NR compounds, we will 4A expand the use of heat-treated Ag residues as bio-based reinforcing fillers, emphasizing the use of biochar fillers. In 4B we will develop methods for NR biodegradation to address an urgent Stakeholder need. Standard methods for biodegradability of NR under composting, marine, and roadside conditions will focus on respirometry.