Biology subjects

Jardine, K. J.

Publications and source records attributed to Jardine, K. J..

4 recordsLinked to original sources

bioRxiv2022

Extensive plant use of exometabolites

Root exudation has been extensively studied due to its importance in soil carbon cycling and in supporting growth of soil microbes. However, the extent and dynamics of plant uptake of exogenous metabolites is poorly understood. To gain new insights into these processes we used 13C-tracing to characterize plant uptake of exometabolites across a panel of diverse plant species (Arabidopsis thaliana, Brachypodium distachyon, Lotus japonicus, Panicum virgatum, and Kalanchoe fedtschenkoi) grown in sterile hydroponic cultures. The uptake of exometabolites accounted for 23% of the overall B. distachyon carbon budget, and we identified 33 metabolites that were taken up by plants. Counterintuitively, many metabolites had higher uptake rates during the day vs. night. Thirteen of the metabolites from root exudates were found to promote root growth in A. thaliana, including hydroxybenzoate, threonate, N-acetyl-glucosamine, and uracil. Together these results indicate that the root uptake of organics can account for a significant portion of the plant carbon budget and that exogenous small molecules used by plants alter root growth with implications for plant nutrition, organic farming, soil nutrient cycling, and rhizosphere community dynamics.

plant biology↗

bioRxiv2021

Measurement of Volatile Compounds for Real-time Analysis of Soil Microbial Metabolic Response to Simulated Snowmelt

Snowmelt dynamics are a significant determinant of microbial metabolism in soil and regulate global biogeochemical cycles of carbon and nutrients by creating seasonal variations in soil redox and nutrient pools. With an increasing concern that climate change accelerates both snowmelt timing and rate, obtaining an accurate characterization of microbial response to snowmelt is important for understanding biogeochemical cycles intertwined with soil. However, observing microbial metabolism and its dynamics non-destructively remains a major challenge for systems such as soil. Microbial volatile compounds (mVCs) emitted from soil represent information-dense signatures and when assayed non-destructively using state-of-the-art instrumentation such as Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-TOF-MS) provide time resolved insights into the metabolism of active microbiomes. In this study, we used PTR-TOF-MS to investigate the metabolic trajectory of microbiomes from a subalpine forest soil, and their response to a simulated wet-up event akin to snowmelt. Using an information theory approach based on the partitioning of mutual information, we identified mVC metabolite pairs with robust interactions, including those that were non-linear and with time lags. The biological context for these mVC interactions was evaluated by projecting the connections onto the Kyoto Encyclopedia of Genes and Genomes (KEGG) network of known metabolic pathways. Simulated snowmelt resulted in a rapid increase in the production of trimethylamine (TMA) suggesting that anaerobic degradation of quaternary amine osmo/cryoprotectants, such as glycine betaine, may be important contributors to this resource pulse. Unique and synergistic connections between intermediates of methylotrophic pathways such as dimethylamine, formaldehyde and methanol were observed upon wet-up and indicate that the initial pulse of TMA was likely transformed into these intermediates by methylotrophs. Increases in ammonia oxidation signatures (transformation of hydroxylamine to nitrite) were observed in parallel, and while the relative role of nitrifiers or methylotrophs cannot be confirmed, the inferred connection to TMA oxidation suggests either a direct or indirect coupling between these processes. Overall, it appears that such mVC time-series from PTR-TOF-MS combined with causal inference represents an attractive approach to non-destructively observe soil microbial metabolism and its response to environmental perturbation.

microbiology↗

bioRxiv2020

Volatiles defenses of Amazon Azteca ants (repellent ants)

Azteca ants are widely distributed in the neotropics and have been utilized as natural insect repellent for centuries. Azteca oils provide natural defense against herbivores in mutualistic interactions between ants and their host trees. While chemical characterization of oil secretions revealed a composition dominated by iridoids and ketones, the volatile emissions from Azteca ants, and therefore the active gas-phase semiochemicals, remain uncharacterized. In this study, we determined the composition of volatile emissions from a sample of an Azteca ant nest near the Rio Negro in the central Amazon. We found Azteca emissions were composed of a blend of methyl cyclopentyl and methyl cyclopentenyl based volatiles previously identified in Azteca oil extracts as potent alarm pheromones. The ketone 6-methyl-5-hepten-2-one, which also waspreviously identified as a major component of the Azteca oil, was found to be the dominant volatile emitted. For the first time, we report emissions of the highly volatile ketones 2,3-butadione and acetoin from the Azteca nest. Our study has important implications for the better understanding of the ecology and defense strategies of Azteca ants in herbivore defense and provides a base for future commercial applications involving Azteca ant essential oils as natural insect repellents.

plant biology↗

bioRxiv2019

Cell wall O-acetyl and methyl esterification patterns of leaves reflected in atmospheric emission signatures of acetic acid and methanol

Plants emit high rates of methanol (meOH), generally assumed to derive from pectin demethylation, and this increases during abiotic stress. In contrast, less is known about the emission and source of acetic acid (AA). In this study, Populus trichocarpa (California poplar) leaves in different developmental stages were desiccated and quantified for total meOH and AA emissions together with bulk cell wall acetylation and methylation content. While young leaves showed high emissions of meOH (140 mol m-2) and AA (42 mol m-2), emissions were reduced in mature (meOH: 69%, AA: 60%) and old (meOH: 83%, AA: 76%) leaves. In contrast, the ratio of AA/meOH emissions increased with leaf development (young: 35%, mature: 43%, old: 82%), mimicking the pattern of O-acetyl/methyl ester ratios of leaf bulk cell walls (young: 35%, mature: 38%, old: 51%), which is driven by an increase in O-acetyl and decrease in methyl ester content with age. The results are consistent with meOH and AA emission sources from cell wall de-esterification, with young expanding tissues producing highly methylated pectin that is progressively demethyl-esterified. We highlight the quantification of AA/meOH emission ratios as a potential tool for rapid phenotype screening of structural carbohydrate esterification patterns.

plant biology↗