Biology subjects

Carter, C. J.

Publications and source records attributed to Carter, C. J..

4 recordsLinked to original sources

bioRxiv2023

Methods for assessing bee foraging preferences: a short review and a new automated apparatus

Bees are essential pollinators for many plant species, but multiple threats exist to both managed and wild bee populations. Their innate foraging behaviors and food preferences are subjects of intense research since bee nutrition is essential for maintaining hive and colony health. Multiple approaches have been developed to assess bee foraging behavior and associated preferences, but they are often labor-intensive and provide data on a limited number of parameters. In this manuscript, we provide a short review of these methods and present the design, build, and implementation of a new, inexpensive, and automated feeding apparatus capable of recording: (1) number of visits, (2) total food consumed, (3) photos and videos of bee behavior while inside of the feeder, and (4) environmental conditions. The efficacy of this apparatus is demonstrated through preference tests with artificial nectars, while also acknowledging the relative strengths and limitations of this approach.

animal behavior and cognition↗

bioRxiv2021

A cell wall invertase controls nectar volume and sugar composition

Flowering plants produce nectar to attract pollinators. The main nectar sugars are sucrose, glucose, and fructose, which can vary widely in ratio and concentration across species. Brassica spp. produce a hexose-dominant nectar (high in the monosaccharides glucose and fructose) with very low levels of the disaccharide sucrose. Cell wall invertases (CWINVs) catalyze the irreversible hydrolysis of sucrose into glucose and fructose in the apoplast. We found that BrCWINV4A is highly expressed in the nectaries of Brassica rapa. Moreover, a brcwinv4a null mutant has (1) greatly reduced cell wall invertase activity in the nectaries, and (2) produces a sucrose-rich nectar with little hexose content, but (3) with significantly less volume. These results were recapitulated via exogenous application of an invertase inhibitor to wild-type flowers. Honeybees prefer nectars with some sucrose, but wild-type B. rapa flowers were much more heavily visited than those of brcwinv4a, suggesting that the potentially attractive sucrose-rich nectar of brcwinv4a could not compensate for its low volume. These results cumulatively indicate that BrCWINV4A is not only essential for producing a hexose-rich nectar, but also support a model of nectar secretion in which its hydrolase activity is required for maintaining a high intracellular-to-extracellular sucrose ratio that facilitates the continuous export of sucrose into the apoplast via SWEET9. Extracellular hydrolysis of each sucrose into two hexoses by BrCWINV4A also likely creates the osmotic potential required for nectar droplet formation. In summary, modulation of CWINV activity can at least partially account for naturally occurring differences in nectar volume and sugar composition.

plant biology↗

bioRxiv2019

Systems analyses of key metabolic modules of floral and extrafloral nectaries of cotton

Nectar is a primary reward mediating plant-animal mutualisms to improve plant fitness and reproductive success. In Gossypium hirsutum (cotton), four distinct trichomatic nectaries develop, one floral and three extrafloral. The secreted floral and extrafloral nectars serve different purposes, with the floral nectar attracting bees to promote pollination and the extrafloral nectar attracting predatory insects as a means of indirect resistance from herbivores. Cotton therefore provides an ideal system to contrast mechanisms of nectar production and nectar composition between floral and extrafloral nectaries. Here, we report the transcriptome, ultrastructure, and metabolite spatial distribution using mass spectrometric imaging of the four cotton nectary types throughout development. Additionally, the secreted nectar metabolomes were defined and were jointly composed of 197 analytes, 60 of which were identified. Integration of theses datasets support the coordination of merocrine-based and eccrine-based models of nectar synthesis. The nectary ultrastructure supports the merocrine-based model due to the abundance of rough endoplasmic reticulum positioned parallel to the cell walls and profusion of vesicles fusing to the plasma membranes. The eccrine-based model which consist of a progression from starch synthesis to starch degradation and to sucrose biosynthesis was supported by gene expression data. This demonstrates conservation of the eccrine-based model for the first time in both trichomatic and extrafloral nectaries. Lastly, nectary gene expression data provided evidence to support de novo synthesis of amino acids detected in the secreted nectars. One sentence summaryThe eccrine-based model of nectar synthesis and secretion is conserved in both trichomatic and extrafloral nectaries determined by a system-based comparison of cotton (Gossypium hirsutum) nectaries.

plant biology↗

bioRxiv2018

An integrated transcriptomics and metabolomics analysis of the Cucurbita pepo nectary implicates key modules of primary metabolism involved in nectar synthesis and secretion

Nectar is the main reward that flowers offer to pollinators to entice repeated visitation. Cucurbita pepo (squash) is an excellent model for studying nectar biology, as it has large nectaries that produce large volumes of nectar relative to most other species. Squash is also monoecious, having both female and male flowers on the same plant, which allows comparative analyses of nectary function in one individual. Here we report the nectary transcriptomes from both female and male nectaries at four stages of floral maturation. Analysis of these transcriptomes and subsequent confirmatory experiments revealed a metabolic progression in nectaries leading from starch synthesis to starch degradation and to sucrose biosynthesis. These results are consistent with previously published models of nectar secretion and also suggest how a sucrose-rich nectar can be synthesized and secreted in the absence of active transport across the plasma membrane. Non-targeted metabolomic analyses of nectars also confidently identified 40 metabolites in both female and male nectars, with some displaying preferential accumulation in nectar of either male or female flowers. Cumulatively, this study identified gene targets for reverse genetics approaches to study nectary function, as well as previously unreported nectar metabolites that may function in plant-biotic interactions.

plant biology↗