Life Science Research Immersion Program Improves STEM-Specific Skills and Science Attitudes among Precollege Students.

A predicted rapid growth in science, technology, engineering, and math (STEM) careers demands a vast and talented workforce, but students most commonly abandon STEM majors within the first 2 years of college. Performance in introductory courses, scientific literacy, and the ability to critically reason are main predictors of retention in STEM, highlighting the importance of precollege and early college experience. The Life Science Research Immersion Program (LSRIP) is a novel science education model that focuses on the development of scientific research skills, thus preparing students for introductory college courses and beyond. To evaluate the efficacy of the LSRIP, pre- and postprogram assessments and surveys were administered to three precollege student cohorts. Scientific reasoning assessment scores improved by 4.70% in Summer 2019 (P < 0.01), 9.44% in Fall 2019 (P < 0.05), and 0.97% in Winter 2020 cohorts, with two of five questions showing statistically significant improvement. Surveyed attitudes toward science improved in 62.9% of questions across all cohorts. These results suggest that research immersion experiences are an effective educational instrument for improving and promoting scientific reasoning and attitudes among precollege students. To better prepare students for success in STEM higher education and careers, we recommend implementing LSRIPs to complement traditional precollege science curricula.

Toxicity assessment of hexafluoropropylene oxide-dimer acid on morphology, heart physiology, and gene expression during zebrafish (Danio rerio) development.

Hexafluoropropylene oxide-dimer acid (HFPO-DA) is one of the emerging replacements for the "forever" carcinogenic and toxic long-chain PFAS. HFPO-DA is a polymerization aid used for manufacturing fluoropolymers, whose global distribution and undetermined toxic properties are a concern regarding human and ecological health. To assess embryotoxic potential, zebrafish embryos were exposed to HFPO-DA at concentrations of 0.5-20,000 mg/L at 24-, 48-, and 72-h post-fertilization (hpf). Heart rate increased significantly in embryos exposed to 2 mg/L and 10 mg/L HFPO-DA across all time points. Spinal deformities and edema phenotypes were evident among embryos exposed to 1000-16,000 mg/L HFPO-DA at 72 hpf. A median lethal concentration (LC50) was derived as 7651 mg/L at 72 hpf. Shallow RNA sequencing analysis of 9465 transcripts identified 38 consistently differentially expressed genes at 0.5 mg/L, 1 mg/L, 2 mg/L, and 10 mg/L HFPO-DA exposures. Notably, seven downregulated genes were associated with visual response, and seven upregulated genes were expressed in or regulated the cardiovascular system. This study identifies biological targets and molecular pathways affected during animal development by an emerging, potentially problematic, and ubiquitous industrial chemical.

Reevaluate how to evaluate: Systemic assessment biases affect students' confidence in college upper-division biology laboratory courses.

Grades influence students' confidence and decisions to complete STEM degrees and pursue relevant careers. What affects students' confidence and performance in college upper-division biology laboratory courses and how relevant are evaluation methods to career success? STEM laboratory courses are an excellent model to address these issues because of the hybrid environment, combining traditional lecture course format and the practical application of knowledge. We surveyed 567 students in two upper-division laboratory molecular biology courses at a major research university to compare course-content self-assessment, students' predicted grades, and actual grades received. By analyzing students' confidence and correlating them to grades assigned by the instructor, we identified biases including student and Instructor Assistant (IA) gender, IA experience, and academic quarter. Considering the systemic effect of identified biases, a correlation (R2  = 0.37, p < 0.01) between predicted and actual grades, and weak but statistically significant correlation (R2  = 0.10, p < 0.01) between students' comprehensive course-content self-assessment and their predicted grade are not surprising. Our analysis suggests that students' quantifiable self-assessment, a relatively simple and data-rich resource, helps identify evaluation bias. If administered periodically throughout the course, these assessments can help mitigate biases, improve student learning, evaluation, and retention in STEM fields.

Relative genetic diversity of the rare and endangered Agave shawii ssp. shawii and associated soil microbes within a southern California ecological preserve.

Shaw's Agave (Agave shawii ssp. shawii) is an endangered maritime succulent growing along the coast of California and northern Baja California. The population inhabiting Point Loma Peninsula has a complicated history of transplantation without documentation. The low effective population size in California prompted agave transplanting from the U.S. Naval Base site (NB) to Cabrillo National Monument (CNM). Since 2008, there are no agave sprouts identified on the CNM site, and concerns have been raised about the genetic diversity of this population. We sequenced two barcoding loci, rbcL and matK, of 27 individual plants from 5 geographically distinct populations, including 12 individuals from California (NB and CNM). Phylogenetic analysis revealed the three US and two Mexican agave populations are closely related and have similar genetic variation at the two barcoding regions, suggesting the Point Loma agave population is not clonal. Agave-associated soil microbes used significantly more carbon sources in CNM soil samples than in NB soil likely due to higher pH and moisture content; meanwhile, soil type and soil chemistry analysis including phosphorus, nitrate nitrogen, organic matter, and metals revealed significant correlations between microbial diversity and base saturation (p < 0.05, r 2 = 0.3676), lime buffer capacity (p < 0.01, r 2 = 0.7055), equilibrium lime buffer capacity (p < 0.01, r 2 = 0.7142), and zinc (p < 0.01, r 2 = 0.7136). Soil microbiome analysis within the CNM population revealed overall expected richness (H' = 5.647-6.982) for Agave species, while the diversity range (1 - D = 0.003392-0.014108) suggests relatively low diversity marked by high individual variation. The most prominent remaining US population of this rare species is not clonal and does not seem to be threatened by a lack of genetic and microbial diversity. These results prompt further efforts to investigate factors affecting Agave's reproduction and fitness.

Structure-function analysis of the maize bulliform cell cuticle and its potential role in dehydration and leaf rolling.

The hydrophobic cuticle of plant shoots serves as an important interaction interface with the environment. It consists of the lipid polymer cutin, embedded with and covered by waxes, and provides protection against stresses including desiccation, UV radiation, and pathogen attack. Bulliform cells form in longitudinal strips on the adaxial leaf surface, and have been implicated in the leaf rolling response observed in drought-stressed grass leaves. In this study, we show that bulliform cells of the adult maize leaf epidermis have a specialized cuticle, and we investigate its function along with that of bulliform cells themselves. Bulliform cells displayed increased shrinkage compared to other epidermal cell types during dehydration of the leaf, providing a potential mechanism to facilitate leaf rolling. Analysis of natural variation was used to relate bulliform strip patterning to leaf rolling rate, providing further evidence of a role for bulliform cells in leaf rolling. Bulliform cell cuticles showed a distinct ultrastructure with increased cuticle thickness compared to other leaf epidermal cells. Comparisons of cuticular conductance between adaxial and abaxial leaf surfaces, and between bulliform-enriched mutants versus wild-type siblings, showed a correlation between elevated water loss rates and presence or increased density of bulliform cells, suggesting that bulliform cuticles are more water-permeable. Biochemical analysis revealed altered cutin composition and increased cutin monomer content in bulliform-enriched tissues. In particular, our findings suggest that an increase in 9,10-epoxy-18-hydroxyoctadecanoic acid content, and a lower proportion of ferulate, are characteristics of bulliform cuticles. We hypothesize that elevated water permeability of the bulliform cell cuticle contributes to the differential shrinkage of these cells during leaf dehydration, thereby facilitating the function of bulliform cells in stress-induced leaf rolling observed in grasses.

Dominant, Heritable Resistance to Stewart's Wilt in Maize Is Associated with an Enhanced Vascular Defense Response to Infection with Pantoea stewartii.

Vascular wilt bacteria such as Pantoea stewartii, the causal agent of Stewart's bacterial wilt of maize (SW), are destructive pathogens that are difficult to control. These bacteria colonize the xylem, where they form biofilms that block sap flow leading to characteristic wilting symptoms. Heritable forms of SW resistance exist and are used in maize breeding programs but the underlying genes and mechanisms are mostly unknown. Here, we show that seedlings of maize inbred lines with pan1 mutations are highly resistant to SW. However, current evidence suggests that other genes introgressed along with pan1 are responsible for resistance. Genomic analyses of pan1 lines were used to identify candidate resistance genes. In-depth comparison of P. stewartii interaction with susceptible and resistant maize lines revealed an enhanced vascular defense response in pan1 lines characterized by accumulation of electron-dense materials in xylem conduits visible by electron microscopy. We propose that this vascular defense response restricts P. stewartii spread through the vasculature, reducing both systemic bacterial colonization of the xylem network and consequent wilting. Though apparently unrelated to the resistance phenotype of pan1 lines, we also demonstrate that the effector WtsE is essential for P. stewartii xylem dissemination, show evidence for a nutritional immunity response to P. stewartii that alters xylem sap composition, and present the first analysis of maize transcriptional responses to P. stewartii infection.