Biology subjects

Stewart, C. G.

Publications and source records attributed to Stewart, C. G..

4 recordsLinked to original sources

bioRxiv2025

Bacteria accumulate more rapidly on shorter lived flowers, but abiotic factors affect flower aging and bacterial accumulation

Outcomes of ecological interactions often depend on the abundance and identity of the organisms involved. Flower-bacteria interactions can strongly affect plant ecology, and the identities of epiphytic flower bacteria are relatively well documented. Yet little is known about how the abundance of epiphytic bacteria on flowers changes over time. In this field study, we quantified how the abundance of culturable epiphytic bacteria on flowers changed as flowers aged and how abiotic factors influenced bacterial abundance and flower longevity. To accomplish this, we sampled flowers from anthesis to senescence of 8 plant species that varied substantially in terms of flower longevity and comprised 8 different genera from 7 different families. As expected, flowers of all plant species accumulated more bacteria with age. However, plant species with longer-lived flowers accumulated bacteria relatively more slowly, suggesting such plant species may have evolved more effective antibacterial defenses. Although elevated temperature is often expected to boost bacterial growth and diminish flower longevity, temperature was negatively associated with both flower longevity and bacterial accumulation, suggesting that changes to flower longevity strongly affect bacterial populations. In contrast, precipitation was positively associated with flower longevity and negatively associated with bacterial accumulation, likely because precipitation reduced plant water stress while also dislodging bacteria from flowers. Finally, we discuss the implications of our results for plant-bacterial-pollinator interactions.

ecology↗

bioRxiv2025

Take it or leaf it: bees learn leaf shape as a cue when flower color is easily learned

Over a century of research has demonstrated that pollinators, such as bees, associatively learn diverse flower cues, including tactile, visual, and olfactory cues, to find food rewards. However, floral cues are not always reliable, as flowers of different plant species often differ in terms of the qualities of their food rewards, even when flower types resemble each other. At the same time, some non-floral traits, such as leaf shape, differ reliably among plant species and might be associatively learned by bees to improve foraging success. In this laboratory study, we tested whether generalist bees (Bombus impatiens) can (1) associatively learn differences in leaf shape to discriminate rewarding from unrewarding flowers and (2) rely more on differences in leaf shape when a flower color cue is harder to discriminate. We therefore assigned bees to either of two treatments: in one treatment, rewarding and unrewarding artificial targets ( flowers) differed greatly in petal color, and in the other treatment, they differed little; each treatments targets differed in leaf shape in the same way. As expected, bees learned significantly faster when flower petal colors were more dissimilar and thus relatively easier to discriminate. These bees also learned and recalled the correct combination of petal color and leaf shape. Yet when petal colors differed relatively little, bees had a much harder time learning petal color and did not show evidence of having remembered leaf shape. Our results demonstrate that leaf shape is a cue that foraging bees can learn to associate with a pollen food reward. However, leaf shape may be learned secondarily to, or only in combination with floral cues (such as petal color). We discuss evidence of compound learning and overshadowing and implications of our results for pollinator-mediated selection on non-floral plant traits.

animal behavior and cognition↗

bioRxiv2024

Mucociliary Clearance is Impaired in Small Airways of Cystic Fibrosis Pigs

RationaleCystic fibrosis is a genetic disorder characterized by recurrent airway infections, inflammation, and progressive decline in lung function. Autopsy and spirometry data suggest that cystic fibrosis may start in the small airways which, due to the fractal nature of the airways, account for most of the airway tree surface area. However, they are not easily accessible for testing. ObjectivesHere, we tested the hypothesis that mucociliary clearance is abnormal in the small airways of newborn cystic fibrosis pigs. MethodsCurrent mucociliary clearance assays are limited therefore we developed a dynamic positron emission tomography scan assay with high spatial and temporal resolution. Each study was accompanied by a high-resolution computed tomography scan that helped identify the thin outer region of the lung that contained small airways. Measurements and Main ResultsClearance of aerosolized [68Ga]macro aggregated albumin from distal airways occurred within minutes after delivery and followed a two-phase process. In cystic fibrosis pigs, both early and late clearance rates were slower. Stimulation of the cystic fibrosis airways with the purinergic agonist UTP further impaired late clearance. Only 1 cystic fibrosis pig treated with UTP out of 6 cleared more than 20% of the delivered dose. ConclusionsThese data indicate that mucociliary transport in the small airways is fast and can easily be missed if the acquisition is not fast enough. The data also indicate that mucociliary transport is impaired in small airways of cystic fibrosis pigs. This defect is exacerbated by stimulation of mucus secretions with purinergic agonists.

physiology↗

bioRxiv2021

Performance of a scalable extraction-free RNA-seq method

RNA sequencing enables high-contents/high-complexity measurements in small molecule screens performed on biological samples. Whereas the costs of DNA sequencing and the complexity of RNA-seq library preparation and analysis have decreased consistently, RNA extraction remains a significant bottleneck for RNA-seq of hundreds of samples in parallel. Direct use of cell lysate for RNA-seq library prep is common in single cell RNA-seq but not in bulk RNA-seq protocols. Recently published protocols suggest that direct lysis is compatible with simplified RNA-seq library prep. Here, we evaluate the performance of a bulk RNA-seq library prep protocol optimized for analysis of many samples of adherent cultured cells in parallel. We combine a low-cost direct lysis buffer compatible with cDNA synthesis ("in-lysate cDNA synthesis") with Smart-3SEQ and examine the effects of calmidazolium and fludrocortisone-induced perturbation of primary human dermal fibroblasts. We compared this method to normalized purified RNA inputs from matching samples followed by Smart-3SEQ or Illumina TruSeq library prep. Our results show that whereas variable RNA inputs for each sample in the in-lysate cDNA synthesis protocol result in variable sequencing depth, this had minimal effect on data quality, measurement of gene expression patterns, or generation of differentially expressed gene lists. We found that in-lysate cDNA synthesis combined with Smart-3SEQ RNA-seq library prep allows generation of high-quality data when compared to library prep with extracted RNA, or when compared to Illumina TruSeq. Our data show that small molecule screens using RNA-seq are feasible at low reagent and time costs.

genomics↗