Biology subjects

McGrath, J. M.

Publications and source records attributed to McGrath, J. M..

7 recordsLinked to original sources

bioRxiv2026

Nutrient Concentration Declines but Nutrient Yield Increases Under Elevated CO2 Concentration in Soybean: Disentangling the relative effects of Dilution, Transpiration, and Uptake Activity

Rising atmospheric CO2 concentrations consistently reduce mineral concentrations in C crops, yet the mechanisms driving this decline - dilution, reduced transpiration-driven mass flow, and altered root nutrient acquisition capacity - have rarely been tested simultaneously under field conditions. Here, we grew two soybean (Glycine max Merr.) varieties with contrasting yield responses to elevated [CO2] (Loda and HS93-4118) at the Soybean Free Air CO2 Enrichment (SoyFACE) facility and quantified the independent contributions of dilution, transpiration, and root uptake to observed changes in tissue mineral concentration and nutrient yield. Elevated [CO2] increased grain yield by 21% and 6% in Loda and HS, respectively, and reduced transpiration by 13-14% across both varieties. A decomposition analysis revealed that while dilution and reduced transpiration each exerted negative effects on tissue nutrient concentrations, with their combined effect representing a 31-40% potential reduction in whole-plant concentration, active root uptake responses were positive for nearly all nutrients, largely offsetting these losses and resulting in observed concentration declines substantially smaller than either mechanism alone would predict. Consequently, whole-plant nutrient yield increased under elevated CO2 for all elements measured, and grain nutrient yield increased for most. The relationship between seasonal transpiration and nutrient yield was steeper under elevated CO2 for most macronutrients, indicating that plants acquired more nutrients per unit water transpired, not less, under elevated CO2. These results demonstrate that root uptake is the dominant compensatory response to elevated [CO2] driven dilution and reduced mass flow in soybean, that nutrient yield is maintained or increased for most elements under elevated [CO2], and that Fe represents a physiologically and nutritionally significant vulnerability in future CO2 environments.

plant biology↗

bioRxiv2026

A decline in skeletal muscle NOX4 abrogates adaptive homeostasis and exacerbates ageing

A decline in NFE2L2-orchestrated adaptive homeostasis and oxidative distress are thought to be key features of ageing. In contracting skeletal muscle, the ROS-producing enzyme NADPH oxidase 4 (NOX4) is a potent inducer of NFE2L2 adaptive homeostasis. Here we report that skeletal muscle NOX4 levels decline in aged mice and humans, resulting in abrogated NFE2L2 adaptive homeostasis, increased protein oxidative damage and decreased muscle function. We show that deleting NOX4 in skeletal muscle exacerbates the physiological decline associated with ageing, resulting in overt sarcopenia and frailty, characterised by physical inactivity, increased adiposity, systemic inflammation, whole-body insulin resistance and advanced liver disease in aged chow-fed mice. The systems-wide physiological decline in aged skeletal muscle NOX4-deficient mice could be corrected by activating NFE2L2 with sulforaphane and reinstating adaptive homeostatic responses otherwise induced by exercise. Our findings provide important insights into the basis for the decline in NFE2L2-orchestrated adaptive homeostasis with age and identify key mechanisms by which exercise may promote healthy ageing.

physiology↗

bioRxiv2025

Evaluation of LiDAR-based Canopy Trait Estimation in Midwestern Row Crops

Stand count, the number of plants per unit ground area, and leaf area index (LAI), the ratio of leaf area to ground area, are critical traits for crop research but are traditionally measured using labor-intensive methods. While new sensing technologies are being developed, quantifying improvement in measurement efficiency and data quality, relative to traditional techniques, is lacking. In this study, we use LiDAR to generate 3D scans of corn and soybean plots and evaluate two computational methods: a gap fraction approach to estimate LAI and a persistent homology algorithm to estimate stand count by detecting structural peaks in the canopy. Validation experiments and statistical comparisons of bias and variance demonstrate that LiDAR-derived LAI estimates in corn are comparable in quality to those from established instruments. However, in soybean, the LiDAR method performs poorly, likely due to dense canopies limiting light penetration and structural differentiation. Stand count estimations in corn closely match manual counts, with the added benefit of full-plot coverage and significantly faster data collection. In soybean, stand count estimates are unreliable under dense canopy conditions. These results offer practical guidance for the use of LiDAR in field phenotyping and highlight both its current capabilities and limitations. While a trade-off between speed and precision remains, particularly in high-density canopies, LiDARs scalability and multi-trait potential make it a promising tool for high-throughput breeding programs. Continued improvements in LiDAR hardware and algorithm design may further enhance measurement accuracy and extend applicability across crops and growth stages.

plant biology↗

bioRxiv2025

Widely Used Variants of the Farquhar-von-Caemmerer-Berry Model Can Cause Errors in Parameter Estimation

AO_SCPLOWBSTRACTC_SCPLOWThe Farquhar-von-Caemmerer-Berry (FvCB) model is the most widely-used mechanistic model of C3 net CO2 assimilation, and it plays a significant role in plant physiology, ecology, climate science, and Earth system modeling. As use of the model has grown, multiple variants have appeared across publications. Although many of these are commonly used, there has not been a detailed investigation of existing variants and their impacts on results and interpretations. Here we summarize the types of variants and their prevalence in the literature, and we present a comprehensive comparison of differences between them. A key finding is that a common variant that uses the minimum of assimilation rates rather than the minimum of carboxylation rates, which we call the "min-A variant," makes different predictions than the original "min-W variant," yet appears in approximately half of highly-cited publications and software tools that use the FvCB model. Another concern is that although leaf biochemistry restricts the range of CO2 partial pressures where limitations due to triose phosphate utilization (TPU) can occur, this restriction is commonly omitted from the models equations. Among other potential issues, these variations can introduce errors exceeding 20% when estimating photosynthetic parameter values from CO2 response curves. It is therefore important to be aware of this source of error when fitting the model, to avoid using the min-A variant, and to include the biochemically-derived CO2 threshold for TPU limitations. CO_SCPLOWENTRALC_SCPLOW TO_SCPLOWHEMEC_SCPLOWO_SCPCAP C_SCPCAPO_SCPLOWOFC_SCPLOWO_SCPCAP C_SCPCAPO_SCPLOWTHEC_SCPLOW MO_SCPLOWANUSCRIPTC_SCPLOWThe Farquhar-von-Caemmerer-Berry model of CO2 assimilation plays a key role in plant research, but many publications use variants of the model that differ from the original and can potentially introduce errors in photosynthetic parameter estimates. NO_SCPLOWOVELC_SCPLOW RO_SCPLOWESULTSC_SCPLOW, IO_SCPLOWDEASC_SCPLOWO_SCPCAP, C_SCPCAPO_SCPLOWORC_SCPLOW MO_SCPLOWETHODSC_SCPLOWUsing a literature survey, FvCB model variants are categorized, and some are found to make contradictory predictions. Comparisons against A-Ci curves show that the "min-W variant" exhibits the best performance, especially at low CO2 concentrations.

plant biology↗

bioRxiv2024

Signatures in domesticated beet genomes pointing at genes under selection in a sucrose-storing root crop

The genus Beta encompasses important crops such as sugar, table, fodder, and leaf beets. All cultivated beets are believed to have originated from the wild sea beet, B. vulgaris subsp. maritima. Sugar beet, a recent crop dating back nearly 200 years, was selectively bred for enhanced root yield in combination with high sucrose content. We assembled a Beta diversity panel comprising wild and cultivated beet accessions. Whole-genome sequencing identified 10.3 million SNP markers. Four distinct genetic clusters were identified: table beet, sugar beet, Mediterranean sea beet, and Atlantic sea beet. A phylogenetic analysis revealed that cultivated beet accessions were genetically closer to Mediterranean than to Atlantic sea beet and that cultivated beets producing storage roots share a common ancestor. Cultivated beets exhibited genome regions with reduced nucleotide diversity compared to Mediterranean sea beets, indicating selection signatures. These regions contained putative candidate genes with potential roles in root development, suppression of lateral root formation, flowering time, and sucrose metabolism. A yet unknown sucrose transporter on chromosome 6 showed reduced nucleotide diversity exclusively in sugar beet accessions compared to other Beta types with low sucrose content, suggesting its role in sucrose storage. Within a region of high nucleotide diversity between accessions with contrasting root phenotypes, we found two genes encoding auxin response factors, which play a crucial role in root development. We reason these genes to be significant root thickening regulators in root crops.

genomics↗

bioRxiv2022

Reducing chlorophyll level in seed filling stages results in higher seed nitrogen without impacting canopy carbon assimilation

Chlorophyll is the major light absorbing pigment for plant photosynthesis. While evolution has selected for higher chlorophyll content in leaves, previous work suggests that domesticated crops grown in modern agricultural environments overinvest in chlorophyll production thereby lowering light use and nitrogen use efficiency. To investigate the potential benefits of reducing chlorophyll level, we created ethanol inducible RNAi tobacco mutants that suppress Mg-chelatase subunit I (CHLI) with small RNA (sRNA) within 3 hours of induction and reduce chlorophyll within 5 days in field conditions. We initiated chlorophyll reduction later in plant development to avoid the highly sensitive seedling stage, and to allow young plants to have full green leaves to maximize light interception before canopy formation. This study demonstrated that >60% reduction of leaf chlorophyll could be tolerated without penalty on above-ground biomass or canopy photosynthesis in field conditions. Leaf chlorophyll reduction during seed filling stages increased tobacco seed nitrogen concentration as much as 17%, while biomass and seed yields were maintained. These results indicate that time-specific reduction of chlorophyll could be a niche strategy that decouples the inverse relationship between yield and seed nitrogen by utilizing saved nitrogen from the reduction of chlorophyll while maintaining full carbon assimilation capacity.

plant biology↗

bioRxiv2020

A contiguous de novo genome assembly of sugar beet EL10 (Beta vulgaris L.)

A contiguous assembly of the inbred EL10 sugar beet (Beta vulgaris ssp. vulgaris) genome was constructed using PacBio long read sequencing, BioNano optical mapping, Hi-C scaffolding, and Illumina short read error correction. The EL10.1 assembly was 540 Mb, of which 96.7% was contained in nine chromosome-sized pseudomolecules with lengths from 52 to 65 Mb, and 31 contigs with a median size of 282 kb that remained unassembled. Gene annotation incorporating RNAseq data and curated sequences via the MAKER annotation pipeline generated 24,255 gene models. Results indicated that the EL10.1 genome assembly is a contiguous genome assembly highly congruent with the published sugar beet reference genome. Gross duplicate gene analyses of EL10.1 revealed little large-scale intra-genome duplication. Reduced gene copy number for well-annotated gene families relative to other core eudicots was observed, especially for transcription factors. Variation in genome size in B. vulgaris was investigated by flow cytometry among 50 individuals drawn from EL10 progeny and three unrelated germplasm accessions, producing estimates from 633 to 875 Mb/1C. Read depth mapping with short-read whole genome sequences from other sugar beet germplasm suggested that relatively few regions of the sugar beet genome appeared associated with high-copy number variation.

genomics↗