Researchers at the University of California, Davis have discovered an Arthrobacter bacterial strain that promotes suberization of the endodermis in sorghum roots. Suberin, a poly-fatty acid polymer, acts as a physical barrier in sorghum roots, helping to prevent infection by the parasitic plant Striga hermonthica, a significant threat to sorghum production. These microbial-based solutions offer a cost-effective and easily deployable strategy to manage Striga infection in the predominantly smallholder farmer-driven sorghum cultivation of sub-Saharan Africa.

Drs. Schroeder and Takahashi of UC San Diego have discovered and characterized a stomatal CO2 sensor and the underlying mechanism in plants. This unique plant CO2 sensor shows very strong phenotypes in mutants, with complete lack of a CO2 response. Moreover, the researchers can reconstitute this CO2 sensor with the recombinant protein complex in vitro. They are using this discovery to further develop genetic applications to modify CO2 sensing and water use efficiency in plants. The researchers have identified two protein kinases, which regulate a Raf-like protein kinase which in turn controls another Raf-like kinase activity in response to change in CO2/bicarbonate concentration in vitro. Mutants in each of these proteins completely disrupt CO2 responses in plants, consistent with our CO2 sensor findings. Biochemical structure analyses reveal important phosphorylation sites and provide insight into the direct CO2 sensing and signaling core mechanism in plant cells.

Researchers at UC Berkeley have developed methods to deliver biomolecules to plant cells using new plant-derived cell penetrating peptides (CPPs). Despite the revolution in DNA editing that the last decade has brought, plant genetic engineering has not been able to benefit to the same extent. This is due to certain challenges in plant physiology that limit the delivery of exogenous protein cargos, as required in the CRISPR-Cas9 system, primarily due to the plant cell wall. In mammalian cells, for instance, cargo delivery can be accomplished using cell-penetrating peptides (CPPs) which are short peptides that facilitate the transport of cargo molecules through the plasma membrane to the cytosol. While this technology has been optimized in mammalian cells, few have studied the delivery of CPPs in plants to verify whether the cell wall is permissible to these materials. Another barrier to the use of nanotechnologies for plant biomolecule delivery is the lack of quantitative validation of successful intracellular protein delivery. The near universal dependence on confocal microscopy to validate delivery of fluorescent proxy cargoes can be inappropriate for use in plants due to various physiological plant properties, for example intrinsic autofluorescence of plant tissues. Therefore, there exists an unmet need for new materials and methods to deliver biomolecules to plant cells and to confirm the delivery of proteins of varying sizes into walled plant tissues. Stage of Research The inventors have developed methods to deliver proteins into plant cells using cell penetrating peptides which are appropriate for use with CRISPR-Cas9 technology, siRNAs, zinc-finger nucleases, TALENs, and other DNA editing methods. They have also developed a biomolecule fluorophore-based assay to accurately quantitate protein delivery to plants cells.Stage of DevelopmentResearch - in vitro 

Professor Julia Bailey-Serres and colleagues from the University of California, Riverside have identified transcription factors involved in the synthesis and modulation of suberin in plants. These transcription factors can be gene-edited or otherwise engineered in rice or other monocot crops to alter suberin production – which can lead to development of new rice cultivars with enhanced tolerance to stresses ranging from increased soil salinity to drought to pest. Fig 1: Fluorol Yellow (FY) staining of rice crown roots for suberin in longitudinal views of the exodermis and radial cross sections under environmental conditions of well-watered (CON) or water deficit (WD).

Prof. Sean Cutler and colleagues at the University of California, Riverside have engineered a system and methods to induce gene expression in plants and organisms, including mammals, using the chemical compound mandipropamid. Using the PYR/PYL/HAB1 promoter system, the PYR1/HAB1 system is reprogrammed to be activiated with mandipropamid.  When the PYR1/HAB1 system dimerizes through chemical induced dimerization (CID) with mandipropamid, the system functions as a control switch for gene expression. This technology has been demonstrated to advantageously accelerate citrus breeding.  It may be applied to improve CAR T-cell therapy and agricultural crops. Fig 1: UCR’s PYR1/HAB1 system is programmed through chemical induced dimerization (CID) initiated by mandipropamid to function as a switch for agrochemical control of gene expression.  

Prof. Hailing Jin and colleagues from the University of California, Riverside have identified genetic negative immune regulators that control the natural immune responses in citrus against HLB. Decreasing or removing these immune regulators may lead to citrus plants that are tolerant and/or resistance to HLB. The development of HLB resistant citrus plants is less expensive and a more efficient long term solution compared to current HLB management strategy, which includes removing infected trees and/or applying pesticides to lower the ACP population. Fig 1:Nicotiana benthamiana (Nb) model plants after exposure to HLB-like infection for 5 days. The plant with its VAD gene knocked-down (siVAD) expresses resistance to the HLB-like infection. The control plant (iRB control) is pictured on the left and is less resistant to the HLB-like infection. 

Researchers at the University of California, Davis have identified specific genetic modifications to plants that impart a variety of advantages based on modulating the presence of suberin

Researchers at the University of California, Davis have developed a pepper plant that abscises its pedicel easily during harvesting, also known as destemming or decapping.

Prof. Kaloshian and her colleagues from the University of California, Riverside, have developed plants with enhanced immunity resulting in enhanced resistance to RKNs. The methods comprise introducing into a plant a gene editing construct that specifically inhibits activity of G-LecRK-VI.13 gene, a negative regulator of plant immunity. Additionally, the descendant of this plant also carry the enhanced resistance to RKNs. The invention could be used in a broad range of important agricultural crops including rice, lettuce, and tomatoes. This approach holds potential for increasing crop quality and yield, considering that plant damage from RKNs result in poor growth, a decline in quality and yield of the crop, and reduced resistance to environmental stresses. By triggering an enhanced immune response, by eliminating a negative regulator of immunity, the opportunity exists to develop more durable plant resistance towards RKNs and other types of nematodes.  Fig 1: Tomato plants, grown in a plastic house, infected with the root-knot nematode Meloidogyne incognita.  

The response of plants to reduced water availability is controlled by a complex osmotic stress and abscisic acid (ABA)-dependent signal transduction network. The core ABA signaling components are snf1-related protein kinase2s (SnRK2s) which are activated by ABA-dependent inhibition of type 2C protein phosphatases and by an unknown ABA-independent osmotic stress signaling pathway. Limited water availability is one of the key factors that negatively impacts crop yields. The plant hormone abscisic acid (ABA) and the signal transduction network it activates, enhance plant drought tolerance through stomatal closure, and inhibition of seed germination and growth. As plants are constantly exposed to changing water conditions, reversibility and robustness of the ABA signal transduction cascade is important for plants to balance growth and drought stress resistance. Core ABA signaling components have been established the ABA receptors PYRABACTIN RESISTANCE (PYR/PYL) or REGULATORY COMPONENT OF ABA RECEPTOR (RCAR) inhibit type 2C protein phosphatases (PP2Cs) resulting in the activation of the SnRK2 protein kinases SnRK2.2, 2.3 and OST1/SnRK2.6 . However, it has remained unclear whether direct autophosphorylation or trans-phosphorylation by unknown protein kinases re-activates these SnRK2 protein kinases in response to stress. The osmotic stress sensing mechanism and upstream signal transduction mechanisms leading to SnRK2 activation remain largely unknown in plants.

Researchers at the University of California, Davis and the Institute of Molecular and Cellular Biology of Rosario in Argentina have collaborated to develop methods for improving plant regeneration efficiency using transformations via a GRF, a GIF, or a GRF-GIF chimera. 

Mutated versions of Cas12a that remove its non-specific ssDNA cleavage activity without affecting site-specific double-stranded DNA cutting activity. These mutant proteins, in which a short amino acid sequence is deleted or changed, provide improved genome editing tools that will avoid potential off-target editing due to random ssDNA nicking.

Researchers at the University of California have identified new modified versions of the carbon fixing enzyme, Phosphoenolpyruvate carboxylase (PPC).  in planta results show that the modified PPC enzymes confer upwards of a five fold increase in carbon fixation when compared to wild type plants. PPC dependent carbon fixation is key to photosynthesis, production of nutrients, and plants conditioning their growth environment. Plants with modified PPCs that increase carbon fixation and photosynthetic output will have increased plant productivity, which is critical for feeding a growing population. Additionally, by identifying surgical changes that can unleash the full productivity of plant PPC’s, it will be possible to increase the rate of depletion of atmospheric CO2.  The combination of these outcomes represents the opportunity to boost agricultural productivity, increase the amount of agriculturally available land by upwards of 100%, and improve the nutritional quality of plants all of which are dependent on removal of CO2 from our atmosphere.  Fig. 2 in vitro comparison of wild type (wt) and modified versions of maize PPC1, which is key to C4 photosynthesis, in the absence or presence of increasing amounts of the allosteric inhibitor, malate. Whereas version A is less affected by malate than wt, both versions B and C are largely unaffected by malate and have a 2-fold increase in activity compared to the wt version.  

Researchers at the University of California, Davis have developed a method of cell-specific degradation of centromeric proteins to induce haploid.

Background: Brassinosteroids are essential plant hormones that control growth and development, in addition to playing a critical role in response to stress and infections. Brassinosteroids also induce ethylene synthesis and are therefore related to senescence and ripening. The major overarching issue involves strictly controlling brassinosteroid response in order to promote growth yet limit other negative effects of brassinosteroids.  Brief Description: UCR researchers have identified three compounds that alter brassinosteroid signaling in plants. These chemicals were found to increase the effects of limited brassinosteroids found under normal conditions yet reduce the effects of excess brassinosteroids. This includes promotive effects on plant height, which increase by 100% due to the chemical enhancing the impact of endogenous brassinosteroids. In contrast, the extreme effects seen with addition of high levels of brassinosteroids are substantially reduced upon addition of this chemical, indicating that this chemical may be useful for modulating the effects of brassinosteroids. In conjunction with this, treatment with the chemical resulted in reversal of several ethylene dependent growth phenomena that are also regulated by brassinosteroids. Currently, there is a huge unmet need in the agricultural sector since treatments that modulate brassinosteroid-regulated phenomena do not exist.

Background: Due to the rapidly increasing demand of food production, agricultural biotechnology companies are aiming to improve crop productivity. Biotechnology tools that develop novel plant traits are projected to have a $1.3B global market with annual growth of 49.9% by 2019.  Brief Description: UCR Researchers have developed a drug-like compound, HTC, that is structurally distinct from other agrochemicals and will rapidly induce an immune response in plants to ward off pathogens. Only a small dose of this novel compound is needed for optimal protection as well as growth enhancement. By genetically engineering the plant to have a stronger inherent immune system, toxic chemicals like pesticides are no longer needed to protect the plant. Its implementation can render decreased usage of agrochemicals that are harmful to humans and the environment.

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Researchers at UC Davis have produced a non-dormant alfalfa line highly amenable to transformation, allowing direct improvement of the line. Higher transformation efficiency and a non-dormant life-cycle make this line of alfalfa a valuable tool for research and breeding.

Background: Citrus greening disease, also known as Huanglongbing (HLB), is a bacterial disease caused by insect-transmission and phloem-limited bacterial pathogens. It is a serious threat to the global citrus industry, decimating many citrus trees and costing the economy billions in damages annually. The most commonly used method of nucleic-acid based pathogen detection is not ideal with low-titer (low concentration of antibodies to antigen) and it cannot detect the erratic distribution of the bacterial pathogens.   Brief Description: UCR researchers have developed a proof-of-concept for using secreted proteins of bacterial pathogens to detect bacterial diseases. These abundant and stable secreted proteins serve as robust detection markers for immunoassay-based diagnostics. Compared to current methods, this novel method is more high-throughput, economical, and able to monitor the pathogens dispersed throughout the plant transportation system.

Background: Citrus greening disease, also known as huanglongbing (HLB), has been a serious, pervasive problem caused by a multitude of plant pathogens. It has decimated many citrus trees, drastically decreasing orange production and costing the US economy an estimated $11B every year. Currently, there is no cure for HLB, so the citrus industry is in dire need for a cost-effective method of early HLB detection.  Brief Description: UCR Researchers have developed a means to detect and identify multiple plant pathogens for disease diagnosis, including citrus greening disease. By developing a novel multiplex RNA assay, they discovered ten targets of nine citrus pathogens and a citrus control gene. In addition to the assays, target-specific probes were designed and implemented to improve the pathogen detection process. These assays were also coupled with high-throughput robotic extraction and purification procedures, optimized for citrus tissues. Furthermore, they also developed a 3-plex DNA assay system along with 3 targets for simultaneous detection, identification and quantification of plant pathogens.

Pamela Ronald and researchers at the Joint BioEnergy Institute (JBEI) have discovered raxX, a novel peptide that activates the Xa21 immune response pathway, capable of conferring robust disease resistance, and methods for its use. Application of the peptide activates the plant immune responses and eliminating bacterial infection. Engineering plants to express both raxX and Xa21 under an inducible control is expected to lead to robust resistance in diverse plant species.

Dr. Steve Jacobsen and colleagues in UCLA’s Department of Molecular, Cell, and Developmental Biology and the Howard Hughes Medical Institute have developed novel methods and compositions for targeted genetic repression in plants. The technology has broad agricultural applications.    

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