Poster session presenters

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Christian BowmanPosition, Lab: Graduate Researcher, Baird LabContact: christian.bowman@ucr.edu | @csbowmanTitle: Improving selection for drought tolerance in bermudagrass using prolonged drought conditions
Abstract: Changing climates are causing a shift in the way water for irrigation is viewed. This is especially impactful for ornamental crops such as turfgrasses, where regions like the southwestern United States have imposed restrictions on water for irrigation used by the public. Water use restrictions are only expected to become more severe, underscoring the necessity for incorporating and improving turfgrass species that are more drought tolerant into urban settings, such as bermudagrass (Cynodon spp.). To improve breeding efforts for drought tolerance, we propose the use of drought conditions in the field for prolonged and repeated periods of time. We recorded the amount of living green tissue, overall plant health, and a visual evaluation of plant quality over the course of this three year study. Under these selection conditions, we showcase the efficacy of bermudagrass in tolerating drought stress while also demonstrating the influence of imposing consecutive drought periods.

Andrea RomeroPosition, Lab: Graduate Researcher, Groen LabContact: arome109@ucr.edu | @idig.wormsTitle: Detecting the genetic basis of constitutive and induced defense responses against root knot nematodes
Abstract: Every year farmers risk the loss of crop plant yield due to infections of plant roots by microscopic root-knot nematodes defined by the root galls it creates at feeding sites. Current methods of chemical control are expensive and not targeted enough to prevent off-target effects on other animals. Understanding how plants prime and ready themselves prior to infection can allow us to identify better options for control, including genetic and chemical control. Using natural genetic variation among a panel of diverse accessions of Arabidopsis thaliana I will measure levels of nematode-induced plantdefense responses using two canonical immune system outputs as models: 1) bursts of reactive oxygen species (ROS), and 2) production of secondary metabolites. For the latter, I will measure levels of tryptophan-derived phytoalexins, characteristic for plants in the Brassicaceae, including indole glucosinolates and camalexin. These phenotypic data will be used in genome-wide association (GWA) mapping to identify genetic loci that control variation in nematode-induced defenses as well as a subset of accessions that will be used for RNA-sequencing experiments to define how these loci fit within the context of immune regulatory gene networks. Further functional investigations will continue in finding what causes the variation in how strongly defenses will be induced through this early defense pathway, beginning at perception. Identifying the initial receptor and signaling mechanisms to then further elucidate the changes between defenses.

Aimee UyeharaPosition, Lab: Graduate Researcher, Rasmussen LabContact: auyeh002@ucr.edu | @plantsdonttweetTitle: TANGLED1 recruitment to atypical division sites in maize
Abstract: The orientation of plant cell division is critical for proper growth and development. Plants establish the division site before cell division starts in part through recruitment of proteins that accumulate at the division site such as the microtubule binding protein TANGLED1 (TAN1). Division is completed by a microtubule structure called the phragmoplast, which builds the new cell plate at the division site. Through observations of TAN1-YFP localization in maize mutants with defective divisions, discordia1 (dcd1) and the double mutant discordia1 (dcd1) alternative discordia1 (add1), we show that TAN1-YFP can be recruited to atypical division sites late in division. Interestingly, TAN1-YFP accumulates in aberrant locations following chemical treatments that disrupt actin or split phragmoplasts, suggesting that TAN1 is recruited to the cell cortex through a phragmoplast-based mechanism. These data suggest that cells that divide atypically may recruit last-minute ‘division modules’ of proteins, including TAN1, to complete divisions. Further work will be done to investigate TAN1’s function at atypical division sites.

Allyssa RichardsPosition, Lab: Graduate Researcher, Ezcurra LabContact: arich065@ucr.edu | @desert_allyTitle: Investigating the potential mutualism between "cheating" ants and extrafloral nectary-bearing Ferocactus cylindraceus
Abstract: Barrel cacti face herbivory from both larger and smaller predators like the bighorn sheep and the cactus bug. Spines are a sharp deterrent for larger predators, but they are less effective against smaller threats such as herbivorous insects, creating a need for a secondary form of protection. Extrafloral nectaries (EFNs), nectar-producing glands located outside of the flower, are remarkable adaptations that provide an anti-herbivory defense against smaller predators by employing ants in a defensive mutualism. However, not all ant species participate in this mutualism and some have been labeled as “cheaters” as they harvest nectar without providing their defensive service in return. I hypothesize that the California Barrel Cacti (Ferocactus cylindraceus) inhabited by ants that do not perform a defensive mutualism are instead benefitting from ant occupation through increased nitrogen and carbon content in the soil as well as increased water infiltration rates around roots. This study is being conducted at the Boyd Deep Canyon Desert Research Center in Indian Wells, CA. Soil collected at three points from the base of each cactus site will be analyzed to retrieve carbon and nitrogen isotopic data. This data will be compared on the basis of ant presence to determine significance of the carbon and nitrogen content in the soil. Future experiments will focus on the assessment of water infiltration rates at the same sites and determine the significance of ant colonization on the ability of cactus roots to obtain additional rain water. Understanding the details of these interactions will expand current ecological knowledge on the purpose and function of extrafloral nectaries in barrel cacti.

Jinrui ShengPosition, Lab: Postdoctoral Researcher, Larsen LabContact: jshen041@ucr.edu Title: Improving the output of Phosphoenolpyruvate carboxylases in Zea mays
Abstract: Phosphoenolpyruvate carboxylase (PEPC) catalyzes the fixation of HCO3- to PEP to form oxaloacetate, which is a key precursor for many different biochemical pathways. Studies have shown that C4 photosynthetic PEPCs have evolved from the C3 isoform and are responsible for carbon fixation for synthesis of glucose. C4 PEPCs have increased activity and are less sensitive to the feedback inhibitors malate and aspartate, which bind to C3 PEPCs to reduce activity.
Previous work has identified three alr mutants in Arabidopsis PEPC that increase Al resistance as a result of increased malate production. Those alr mutants cause single amino acid change in PEPC in highly conserved regions. This study focuses on Zea mays, which has both C3 isoform PEPC (PEP7 in roots) and the C4 isoform PEPC (PPC1 in shoots). In vitro enzymatic assays have shown the alr mutants in PPC1 and PEP7 have improved enzymatic efficiency and are less inhibited by malate. alr Transgenic maize would be available soon to test the effect of alr mutants in vivo.

Matthew DuongPosition, Lab: Undergraduate Researcher, Rasmussen LabContact: mduon030@ucr.edu Title: The Effect Of Arabidopsis Callose Synthase Inhibitor Endosidin 7 On Cell Division In Zea mays
Abstract: In plant cells, the cell plate grows radially towards the cell cortex through fusion of vesicles and membrane compartments. Callose is a plant polysaccharide deposited at the cell plate during telophase, serving as a temporary structural component until cell plate maturation. To determine whether disrupting callose accumulation alters localization of key cell plate proteins during cell division, a callose synthase inhibitor Endosidin 7 (ES7) was used. Arabidopsis seedlings were treated with ES7 or the respective DMSO negative control, either through growth in ES7-containing media or 2 hour pulse treatments. ES7 caused cell wall defects like cell wall stubs, cell plate gaps, and multinucleated cells. Similar treatments in Zea mays did not cause cell wall defects, nor changes in cell-plate localization for cell plate markers (RAB1A-CFP, RAB2A-YFP, KNOLLE-YFP, RAB11D-YFP), nor changes in callose deposition. CALLOSE SYNTHASE proteins in maize (CalS3/CalS10) share 71-73% similarity with Arabidopsis CalS1/GSL6. Normal division and protein localization despite ES7 treatment in maize may be attributed to protein differences between maize/Arabidopsis CALLOSE SYNTHASEs or species-specific differences in an ES7 target, e.g. a callose-synthase-interacting protein. Further experiments characterizing the relationship of ES7 and callose synthase will be done to understand cell plate formation in maize.

Eric FochtPosition, Lab: Graduate Researcher, Arpaia LabContact: eric.focht@ucr.edu Title: Field performance of a new promising avocado variety, UCRV_04Abstract: Many California growers rely on “B” flower type pollinizers to enhance yields of ‘Hass’, an “A” flower type variety. Most pollenizers are green-skinned fruit, with lower market value. ‘UCR_V04’ is a new UCR ‘Hass’-like B flower-type cultivar that presents a narrow, upright tree with a consistent, marketable crop. Our objectives were to study its field performance characteristics. 2 field sites, in Southern California and in California’s Central Valley were considered. ‘UCR_V04’ and ‘Hass’ trees along with several other cultivars were planted in both locations in 2013 on Dusa® rootstock. Canopy measurements, yield, and flowering data were recorded over the period 2013 through 2022. ‘UCR_V04’ is a new upright, narrow tree with acceptable yield per tree that could be planted at higher density than ‘Hass’. Additionally, it overlaps well with the “A” flower type cultivars studied in this trial and would be a good potential pollen source.
Title: Sensory characterization of new green skin avocado cultivars over their harvest seasonAbstract: Most avocados grown and marketed in the US are ‘Hass’ which gained prominence in the 1980’s replacing the green-skin variety ‘Fuerte’. ‘Hass’ has desirable properties including a dark skin when ripe that can indicate ripeness and hide blemishes. With increasing consumer sophistication, it is possible that green-skin cultivars could be reintroduced into the marketplace. Our objectives were to evaluate overall sensory acceptance and changes in the flavor profile of two green-skin cultivars developed by UCR: ‘UCR_V08’, and ‘UCR_V06’ against ‘Hass’ during their harvest season. Fruits were ripened with ethylene to ~1.0–1.5 lbf. Overall acceptance (9-point hedonic scale) and CATA (check all that apply) were performed by semi-trained panelists (n=60) during each cultivar’s season. Fruit cubes (1-15 cm3) assigned a 3-digit code were presented to panelists using a complete randomized block design using Compusense®. Statistical analysis was performed (ANOVA, LSD Fisher). Significant differences (p< 0.01) were found between ‘UCR_V08’ and ‘Hass’ acceptability, ranging from 6.45-6.48 (‘UCR_V08’) and 6.06-6.23 (‘Hass’) during November-January. ‘UCR_V08’ creaminess and smoothness increased throughout the season. Its flavor was nutty and sweet in its early season, but oilier and more savory at season’s end. ‘UCR_V06’ acceptability was higher than ‘Hass’ but was not significant (p>0.01; April-August). ‘UCR_V06’ texture was similar to ‘Hass’ but was rated more nutty and greener (April-June), and oilier and more savory than ‘Hass’ at season's end (Aug). These 2 green-skin avocados were found to be acceptable by panelists and could provide a good market alternative to ‘Hass’ in a niche market.

AJ Krieger LodgePosition, Lab: Graduate Researcher, Spasojevic LabContact: alodg001@ucr.edu Title: Using a multi-scale framework to understand variation in plant community assembly across complex landscapes
Abstract: Biodiversity patterns are the result of multiple interacting community assembly processes that operate over multiple spatial scales. Despite decades of research, identifying the appropriate spatial scale at which to study these assembly processes remains challenging, especially in complex landscapes such as mountains. Here, we sought to move beyond identifying the relative importance of different processes and instead identify how those processes shift in importance with scale. Specifically, our goal was to identify the spatial scales at which climatic (e.g., temperature, precipitation), microclimatic (e.g., shading, cold air pooling), and non-climatic (e.g., dispersal, biotic interactions, soils) factors influence patterns of plant biodiversity in the alpine tundra. This study was conducted at the Niwot Ridge Long-Term Ecological Research site in the Colorado Rocky Mountains, USA. To infer how assembly processes changed across scales, we used a spatially explicit sampling design that combined community composition surveys at five spatial scales (n = 3, 9, 27, 81, 324 respectively) with plant trait data, spatial and environmental data, and null models. We found that species diversity and functional diversity increased as spatial scale increased and began to saturate at the largest spatial scales. Moreover, we found that assembly mechanisms shifted within spatial scale. At smaller spatial scales we found evidence for species sorting along soils gradients while at medium and large spatial scales climate and dispersal became more important. Taken together our results suggest that explicitly considering how the mechanisms that create observed patterns of biodiversity vary across scales is critical for understanding patterns of alpine biodiversity and that spatial scale should be more explicitly considered when developing conservation and management strategies in complex landscapes.

Alysha ToomeyPosition, Lab: Graduate Researcher, Weitao Chen LabContact: atoom001@ucr.edu Title: Multiscale Model for Morphogenesis of Pavement Cells in Plant Leaves
Abstract: Pavement cells, the leaf epidermal cells in plants, have complex jigsaw-puzzle piece shapes. The formation of these interlocking shapes relies on mechanical, chemical, and cell-to-cell signals at different scales. Because of this, pavement cells are an interesting model system used to study the mechanisms involved in cell morphogenesis in plant tissue. In order to investigate these mechanisms, a multiscale model is being developed. Utilizing the local level set method, biochemical dynamics on moving cell boundaries are captured. By incorporating cell-cell adhesion and cross talk between neighboring cells, the model will be expanded to a multicellular framework in order to investigate the components involved in establishing these intricate cell shapes.

Mona TranPosition, Lab: Undergraduate Researcher, Mauck LabContact: mtran201@ucr.edu Title: Investigating the bindweed psyllid (Bactericera maculipennis) as a potential vector of Candidatus Liberibacter solanacearum in a previously undescribed host plant (Solanum umbelliferum)
Abstract: Candidatus Liberibacter solanacearum (CLso) is a psyllid-transmitted, unculturable bacterial plant pathogen in the taxon ‘Candidatus’(Ca.) Liberibacter, which is known to threaten crop production and pose food insecurity. Currently, there are 8 described haplotypes of this plant pathogen worldwide: G, F, A, U, E, D, C, and B. Previously, Bactericera (B.) cockerelli, the potato psyllid, was CLso’s only known vector in the U.S.A. Bactericera (B.) maculipennis, the bindweed psyllid, is a recently described vector of CLso. While B. maculipennis’ known host plants are in the ‘bindweed family’ Convolvulaceae, all research up until this point suggested they could not successfully reproduce, nor develop on plants in the Solanaceae, a sister family to their host family. With all this in mind, after finding and collecting B. maculipennis on Solanum (S.) umbelliferum (Solanaceae) in the field, we screened them for CLso and reared them on various Solanaeceous plants to study potential viable reproductive host plants. Our results suggest this particular population of B. maculipennis we collected carries a currently unpublished, novel strain of CLso and has an unexpected reproductive plant host.

Sun Hyun ChangPosition, Lab: Graduate Researcher, Nelson LabContact: schan131@ucr.eduTitle: Identification of a domain that specifies developmental control by the karrikin pathway target, SMAX1
Abstract: Karrikins (KARs) are compounds found in smoke that regulate plant development, similar to the putative plant hormone known as KAI2-ligand (KL). The KAR/KL signaling pathway is similar to that of strigolactones (SLs), sharing homologous receptors, KARRIKIN INSENSITIVE2 (KAI2) and DWARF14 (D14), the F-box protein MAX2, and homologous downstream target proteins in the SMAX1-LIKE (SMXL) family. SMXL proteins function as transcriptional co-suppressors through an EAR motif that mediates interaction with TOPLESS proteins. Targeted degradation of different sister clades of SMXL proteins by the receptors after signal perception activates downstream transcription, causing different developmental responses. For example, SMAX1-clade proteins, which are primarily targeted by KAR/KL signaling, regulate seedling photomorphogenesis and seed germination. SMXL7-clade proteins, which are targeted by SL signaling, control shoot architecture. This raises questions about how SMXL proteins control different developmental responses. To determine whether the different roles of SMAX1 and SMXL7 are due to their expression patterns, we tested whether SMXL7 can replace SMAX1 when controlled by a SMAX1 promoter. Introducing pSMAX1::SMXL7 did not rescue the short hypocotyl phenotype of smax1smxl2. This implied the different developmental roles of SMXL genes may be specified by differences in protein sequence rather than expression patterns, for example by specifying transcription factor partners or genome-binding sites. To identify the source of this specificity, we created a set of chimeric SMXL7 proteins with different domains exchanged with SMAX1, and tested which chimera could rescue smax1smxl2. We discovered a SMAX1 "output" domain (SMAX1OP) that was essential to control seedling development. Furthermore, fusion of SMAX1OP to an EAR-type SRDX motif produced a protein that recreated the developmental function of SMAX1 without its regulation by KAI2. To understand how SMAX1OP controls seedling development, we are now searching for proteins that interact with SMAX1OP and characterizing the transcriptional responses that occur shortly after inducing or removing SMAX1-based repression.

Isaac TatePosition, Lab: Graduate Researcher, Reddy & Chen LabsContact: itate001@ucr.eduTitle: A coupled growth and signalling model for Shoot Apical Meristem in Arabidopsis
Abstract: To further understand how the diffusion of Arabidopsis transcription factors actually occurs, this model seeks to represent the tissue and transcription factor as the cell is growing. This is done by combining two models: one handling the chemical signaling of the transcription factors, and one handling the tissue’s configuration by calculating cellular growth rates and intracellular forces.

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Poster session presenters

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