Biology subjects

McGale, E.

Publications and source records attributed to McGale, E..

7 recordsLinked to original sources

bioRxiv2026

Intricate asymbiotic hyphal interactions of Rhizophagus irregularis revealed with single-plane observations in a new microfluidic device

Arbuscular mycorrhizal fungi (AMF) are essential symbionts to most land plants. There is great interest in using AMF inoculation treatments to enhance restoration or agricultural efforts. However, little is known about AMF asymbiotic interactions that could shape soil ecosystems and inoculation outcomes. Studying these early traits is challenging given the obligate nature of AMF. Microfluidic devices enable high-resolution, single-plane, time-resolved observation of AMF hyphal traits in controlled, plant-less environments. The AMF-AnastomosisChip, introduced in this work, additionally separates spores and hyphae into lanes for detailed observations prior to entering a shared interaction zone. Using this device with Rhizophagus irregularis, we phenotyped key hyphal traits from germination to anastomosis. We compared the effect of a fatty acid (FA) treatment to other environmental factors in shaping AMF growth and fusion (anastomosis). Among our results, we confirm known effects of the FA treatment in increasing hyphal branching and longevity but interestingly show that multiple hyphae in a lane can negate FA effects. We also newly reveal that anastomosis occurs for 100% of interactions among hyphae from different lanes, but only for 50% of in-lane interactions, potentially linked to spore origin. Our findings validate the AMF-AnastomosisChip as a versatile platform for increasing discovery in trait-based microbial ecology, including for asymbiotic AMF interactions with environmental factors. This work sets the foundation for future studies with the AMF-AnastomosisChip on the effects of nutrient content, plant-derived molecules, or microbial community members on the AMF traits characterized in this study.

microbiology↗

bioRxiv2025

Diurnal plant and Rhizophagus irregularis transcriptional patterns are linked to shifts in cassava tissue partitioning in the field

O_LICassava is a globally-important crop whose yields can radically increase with arbuscular mycorrhizal fungi (AMF) inoculation. However, extensive background noise in field environments makes it very challenging to understand how the cassava-AMF symbiosis confers benefits, which is especially important for future applications of AMF treatments. C_LIO_LIIn two field experiments, we combined transcriptomics and allometric analyses to investigate functional variation in cassava-AMF interactions using sterile, single isolates of Rhizophagus irregularis. We developed a novel Index of Symbiotic Transcriptional Activity (ISTA) and accounted for sampling times to reduce transcriptomic noise and improve links to biomass traits. C_LIO_LIISTA significantly correlated with cassava shoot biomass in an isolate-dependent manner, and allometric analyses revealed that R. irregularis isolates can either reinforce or uncouple cassava shoot-root relationships to maximize root yields. Differential expression and co-expression network analyses uncovered isolate-specific plant and fungal gene module responses. Including ISTA and sampling time as random effects enhanced detection of gene candidates, including down-regulated genes linked to higher yield. C_LIO_LIOur study uses novel and translatable transcriptomic tools to readily dissect variably field data, allowing new links to be found between AMF symbiotic functions and cassava yields. C_LI

molecular biology↗

bioRxiv2025

Dissecting mycorrhizal fungal trait variation, its genetic basis and trade-offs

Despite the importance of arbuscular mycorrhizal fungi (AMF) in worldwide ecosystems, there is relatively little controlled phenotyping of their intraspecific fungal trait diversity, which limits our determination of how AMF traits link to their genetic differences. Here, we monitor 33 in vitro fungal traits in a population of 48 genetically diverse isolates of Rhizophagus irregularis, over 18 weeks, across plate compartments with and without direct plant root influence. This study reveals that intraspecific AMF variability is extensive, and that R. irregularis traits are mostly positively correlated, especially in root-free environments. The few trait trade-offs (negative correlations) found existed in proximity to the host root. Given the large screening population and the variance decomposition method of repeatability, we find that the genetic individuality of isolates significantly explained variation in approximately half of the AMF traits measured, and especially those related to hyphal growth, branching structures and reproduction near plant roots. Especially, differences in the frequency and fineness of branching right after growth from the plant host, which did not correlate to nearly any other traits, were explained by isolate identity (i.e., genotype). The new information we reveal on R. irregularis trait relationships, over time and in different environments, as well as trait links to genetic differences among isolates, provides the foundation for future understanding of AMF functional diversity. Our genetic findings also provide critical groundwork for genome wide association studies on the non-plant-related traits of R. irregularis.

ecology↗

bioRxiv2024

QTL mapping in field plant populations reveals a genetic basis for frequency- and spatially-specific fungal pathosystem resistance

Fungal pathogens pose significant challenges to agro-ecosystem productivity. The wild tobacco, Nicotiana attenuata, has been grown for over two decades at an experimental field station in its native habitat, leading to the emergence of a high-mortality sudden wilt disease caused by a Fusarium-Alternaria pathosystem. By using an Advanced Intercross Recombinant Inbred Line (AI-RIL) mapping population of N. attenuata planted in the infected field site, we found two significant loci associated with plant susceptibility to the fungi. A functional characterization of several genes in these loci identified RLXL (intracellular ribonuclease LX-like) as an important factor underlying plant pathogen resistance. Virus-induced silencing of RLXL reduced leaf wilting in plants inoculated with an in vitro culture of Fusarium species. Assessing the significance of the RLXL-associated allele in mixed field populations indicated that, among 4-plant subpopulations, those harboring a single plant with the RLXL-deficiency allele exhibited the highest survival rates. Within these populations, a living RLXL-deficient plant improved the survival of RLXL-producing plants located diagonally, while the mortality of the adjacent plants remained as high as in all other subpopulations. Taken together, these findings provide evidence for the genetic basis for a frequency- and spatially-dependent population pathogen resistance mechanism. Significance statementPlant pathogen resistance studies predominantly focus on single genes that reduce pathogenicity in individual plants, aiming to apply these findings to agricultural monocultures. On the other hand, ecologists have observed for decades that greater diversity drives plant population resistance and resilience to pathogens. More studies are needed to identify and characterize loci with positive effects conferred through their frequency in plant populations. We combine quantitative genetics, molecular techniques, and ecologically-informed mixed field populations to identify a novel intracellular ribonuclease LX-like (RLXL) gene with a frequency- and position-dependent effect for plant resistance. To our knowledge, this is the first detailed link between plant population protection and various percentages of plants with an allele representing RLXL presence or absence.

plant biology↗

bioRxiv2023

Pre-zygotic mate selection affects progeny fitness and is only partially correlated with the expression of NaS-like RNases

O_LINicotiana attenuata styles preferentially select pollen from accessions with corresponding expression patterns of NaS-like-RNases (SLRs), and the post-pollination ethylene burst (PPEB) is an accurate predictor of seed siring success. However, the ecological consequences of mate selection, its effect on the progeny, and the role of SLRs in the control of ethylene signaling are still not well understood. C_LIO_LIWe explored the link between the magnitude of the ethylene burst and transcript and protein abundance of the SLRs in a set of recombinant inbred lines (RILs) and investigated the fitness consequences of mate selection for the next generation. Genome Wide Association Study (GWAS) identified novel candidate genes potentially involved in the control of mate selection. C_LIO_LIWe found that high levels of PPEB are associated with the absence of SLR2 but not with the expression of SLR1 in most of the tested RILs. Maternal genotypes that favor certain pollen produce offspring with longer roots when pollinated with these donors, but the selection for beneficial traits is abolished when the maternal genotype selects only against certain pollen donors. C_LIO_LIWe conclude that mate selection mechanisms affect the offspring number and performance in ways that might be adaptive. C_LI

ecology↗

bioRxiv2020

Allelic differences of clustered terpene synthases contribute to correlated intra-specific variation of floral and herbivory induced volatiles in a wild tobacco

O_LIPlant volatile emissions can recruit predators of herbivores for indirect defence and attract pollinators to aid in pollination. Although volatiles involved in defence and pollinator attraction are primarily emitted from leaves and flowers, respectively, they will co-evolve if their underlying genetic basis is intrinsically linked, either due to pleiotropy or genetic linkage. However, direct evidence of co-evolving defence and floral traits is scarce. C_LIO_LIWe characterized intra-specific variation of herbivory-induced plant volatiles (HIPVs), the key components of indirect defence against herbivores, and floral volatiles in the wild tobacco Nicotiana attenuata. C_LIO_LIWe found that variation of (E)-{beta}-ocimene and (E)--bergamotene contributed to the correlated changes in HIPVs and floral volatiles among N. attenuata natural accessions. Intra-specific variations of (E)-{beta}-ocimene and (E)--bergamotene emissions resulted from allelic variation of two genetically co-localized terpene synthase genes, NaTPS25 and NaTPS38 respectively. C_LIO_LIAnalyzing haplotypes of NaTPS25 and NaTPS38 revealed that allelic variations of NaTPS25 and NaTPS38 resulted in correlated changes of (E)-{beta}-ocimene and (E)--bergamotene emission in HIPVs and floral volatiles in N. attenuata. C_LIO_LITogether, these results provide evidence that pleiotropy and genetic linkage result in correlated changes in defences and floral signals in natural populations, and the evolution of plant volatiles is likely under diffuse selection. C_LI

evolutionary biology↗

bioRxiv2019

Determining the scale at which variation in WUE traits changes population yields

Functional variation is known to influence population yield, but the scale at which this happens is still unknown. Relevant signals might only reach immediate neighbors of a phenotypically diverse plant (neighbor-scale) or conversely may distribute across the population (population-scale). We use Nicotiana attenuata silenced in mitogen-activated protein kinase 4 (irMPK4), plants with low water-use efficiency (WUE), to study the scale at which water-use traits alter intraspecific population yields. In the field and glasshouse, populations with low percentages of irMPK4 plants planted among isogenic control plants produced maximum overall growth and yield. Through paired-plant and local-plant-configuration analyses, we determined that this occurred at the population scale. However, we find that this effect was not due to irMPK4s WUE phenotype. With micro-grafting, we additionally show that MPK4-deficiency may mediate the response at the population-scale: shoot-expressed MPK4 is required for N. attenuata to change yield in response to a neighbor.

ecology↗