Impacts of sample handling and storage conditions on archiving physiologically active soil microbial communities.

Soil microbial communities are fundamental to ecosystem processes and plant growth, yet community composition is seasonally and successionally dynamic, which interferes with long-term iterative experimentation of plant-microbe interactions. We explore how soil sample handling (e.g.

Rhizosphere microbial community composition shifts diurnally and in response to natural variation in host clock phenotype.

Plant-associated microbial assemblages are known to shift at time scales aligned with plant phenology, as influenced by the changes in plant-derived nutrient concentrations and abiotic conditions observed over a growing season. But these same factors can change dramatically in a sub-24-hour period, and it is poorly understood how such diel cycling may influence plant-associated microbiomes. Plants respond to the change from day to night via mechanisms collectively referred to as the internal "clock," and clock phenotypes are associated with shifts in rhizosphere exudates and other changes that we hypothesize could affect rhizosphere microbes.

The rhizosphere microbiome and host plant glucosinolates exhibit feedback cycles in Brassica rapa.

The rhizosphere microbiome influences many aspects of plant fitness, including production of secondary compounds and defence against insect herbivores. Plants also modulate the composition of the microbial community in the rhizosphere via secretion of root exudates. We tested both the effect of the rhizosphere microbiome on plant traits, and host plant effects on rhizosphere microbes using recombinant inbred lines (RILs) of Brassica rapa that differ in production of glucosinolates (GLS), secondary metabolites that contribute to defence against insect herbivores.

Naturally segregating genetic variation in circadian period exhibits a regional elevational and climatic cline.

Circadian clocks confer adaptation to predictable 24-h fluctuations in the exogenous environment, but it has yet to be determined what ecological factors maintain natural genetic variation in endogenous circadian period outside of the hypothesized optimum of 24 h. We estimated quantitative genetic variation in circadian period in leaf movement in 30 natural populations of the Arabidopsis relative Boechera stricta sampled within only 1° of latitude but across an elevation gradient spanning 2460-3300 m in the Rocky Mountains. Measuring ~3800 plants from 473 maternal families (7-20 per population), we found that genetic variation was of similar magnitude among versus within populations, with population means varying between 21.

Spatiotemporal Heterogeneity and Intragenus Variability in Rhizobacterial Associations with Growth.

Microbial communities in the rhizosphere are distinct from those in soils and are influenced by stochastic and deterministic processes during plant development. These communities contain bacteria capable of promoting growth in host plants through various strategies. While some interactions are characterized in mechanistic detail using model systems, others can be inferred from culture-independent methods, such as 16S amplicon sequencing, using machine learning methods that account for this compositional data type.

Aquatic Macrophytes Are Associated With Variation in Biogeochemistry and Bacterial Assemblages of Mountain Lakes.

In aquatic systems, microbes likely play critical roles in biogeochemical cycling and ecosystem processes, but much remains to be learned regarding microbial biogeography and ecology. The microbial ecology of mountain lakes is particularly understudied. We hypothesized that microbial distribution among lakes is shaped, in part, by aquatic plant communities and the biogeochemistry of the lake.

Plastic response to early shade avoidance cues has season-long effect on Beta vulgaris growth and development.

Early-emerging weeds are known to negatively affect crop growth but the mechanisms by which weeds reduce crop yield are not fully understood. In a 4-year study, we evaluated the effect of duration of weed-reflected light on sugar beet (Beta vulgaris L.) growth and development.

Soil Microsite Outweighs Cultivar Genotype Contribution to Rhizobacterial Community Structure.

Microorganisms residing on root surfaces play a central role in plant development and performance and may promote growth in agricultural settings. Studies have started to uncover the environmental parameters and host interactions governing their assembly. However, soil microbial communities are extremely diverse and heterogeneous, showing strong variations over short spatial scales.

A Nested Association Mapping Panel in for Mapping and Characterizing Genetic Architecture.

Linkage and association mapping populations are crucial public resources that facilitate the characterization of trait genetic architecture in natural and agricultural systems. We define a large nested association mapping panel (NAM) from 14 publicly available recombinant inbred line populations (RILs) of , which share a common recurrent parent (Col-0). Using a genotype-by-sequencing approach (GBS), we identified single nucleotide polymorphisms (SNPs; range 563-1525 per population) and subsequently built updated linkage maps in each of the 14 RIL sets.

Rapid Chlorophyll Fluorescence Light Response Curves Mechanistically Inform Photosynthesis Modeling.

Crop improvement is crucial to ensuring global food security under climate change, and hence there is a pressing need for phenotypic observations that are both high throughput and improve mechanistic understanding of plant responses to environmental cues and limitations. In this study, chlorophyll fluorescence light response curves and gas-exchange observations are combined to test the photosynthetic response to moderate drought in four genotypes of The quantum yield of PSII ( ) is here analyzed as an exponential decline under changing light intensity and soil moisture. Both the maximum and the rate of decline across a large range of light intensities (0-1,000 μmol photons m s; ) are negatively affected by drought.

Integrating transcriptomic network reconstruction and eQTL analyses reveals mechanistic connections between genomic architecture and Brassica rapa development.

Plant developmental dynamics can be heritable, genetically correlated with fitness and yield, and undergo selection. Therefore, characterizing the mechanistic connections between the genetic architecture governing plant development and the resulting ontogenetic dynamics of plants in field settings is critically important for agricultural production and evolutionary ecology. We use hierarchical Bayesian Function-Valued Trait (FVT) models to estimate Brassica rapa growth curves throughout ontogeny, across two treatments, and in two growing seasons.

The fitness benefits of genetic variation in circadian clock regulation.

Functional circadian clocks are essential for fitness in diverse ecosystems, facilitating detection of predictable light-dark and temperature cycles. The molecular basis of endogenous clocks is variable across the tree of life, but it has one omnipresent attribute: natural genetic diversity that manifests as variation for instance in circadian period length around the hypothesised optimum of 24 hours. Latitudinal variation in photoperiod alone is unlikely to account for the vast diversity documented in varied organisms, but we have yet to achieve a solid understanding of the interplay between clock variability and natural selection.

A framework for genomics-informed ecophysiological modeling in plants.

Dynamic process-based plant models capture complex physiological response across time, carrying the potential to extend simulations out to novel environments and lend mechanistic insight to observed phenotypes. Despite the translational opportunities for varietal crop improvement that could be unlocked by linking natural genetic variation to first principles-based modeling, these models are challenging to apply to large populations of related individuals. Here we use a combination of model development, experimental evaluation, and genomic prediction in Brassica rapa L.

QTL Underlying Circadian Clock Parameters Under Seasonally Variable Field Settings in .

The circadian clock facilitates coordination of the internal rhythms of an organism to daily environmental conditions, such as the light-dark cycle of one day. Circadian period length (the duration of one endogenous cycle) and phase (the timing of peak activity) exhibit quantitative variation in natural populations. Here, we measured circadian period and phase in June, July and September in three recombinant inbred line populations.

The effect of rhizosphere microbes outweighs host plant genetics in reducing insect herbivory.

Rhizosphere microbes affect plant performance, including plant resistance against insect herbivores; yet, a direct comparison of the relative influence of rhizosphere microbes versus plant genetics on herbivory levels and on metabolites related to defence is lacking. In the crucifer Boechera stricta, we tested the effects of rhizosphere microbes and plant population on herbivore resistance, the primary metabolome, and select secondary metabolites. Plant populations differed significantly in the concentrations of six glucosinolates (GLS), secondary metabolites known to provide herbivore resistance in the Brassicaceae.

Phenotypic Trait Identification Using a Multimodel Bayesian Method: A Case Study Using Photosynthesis in Genotypes.

Agronomists have used statistical crop models to predict yield on a genotype-by-genotype basis. Mechanistic models, based on fundamental physiological processes common across plant taxa, will ultimately enable yield prediction applicable to diverse genotypes and crops. Here, genotypic information is combined with multiple mechanistically based models to characterize photosynthetic trait differentiation among genotypes of .

Circadian rhythms are associated with shoot architecture in natural settings.

Circadian rhythms are key regulators of diverse biological processes under controlled settings. Yet, the phenotypic and fitness consequences of quantitative variation in circadian rhythms remain largely unexplored in the field. As with other pathways, phenotypic characterization of circadian outputs in the field may reveal novel clock functions.

Circadian rhythms are associated with variation in photosystem II function and photoprotective mechanisms.

The circadian clock regulates many aspects of leaf gas supply and biochemical demand for CO , and is hypothesized to improve plant performance. Yet the extent to which the clock may regulate the efficiency of photosystem II (PSII) and photoprotective mechanisms such as heat dissipation is less explored. Based on measurements of chlorophyll a fluorescence, we estimated the maximum efficiency of PSII in light (Fv'/Fm') and heat dissipation by nonphotochemical quenching (NPQ).

Circadian Rhythms and Reproductive Phenology Covary in a Natural Plant Population.

The circadian clock is a molecular timekeeper that matches endogenous rhythms in diverse traits with 24-h cycles in the external environment. Although a lack of clock resonance to the environment is detrimental to performance, clock phenotypes in wild populations nevertheless deviate substantially from the predicted optimal cycle length of 24 h, and significant genetic variation exists for circadian parameters. Here, we describe covariation between 2 traits considered to reflect adaptation to different aspects of temporal environmental heterogeneity, circadian rhythms (adaptation to daily environmental cycles) and flowering time (adaptation to seasonal cycles), in a Rocky Mountain population of the mustard Boechera stricta, a North American relative of Arabidopsis thaliana.

Circadian Rhythms and Redox State in Plants: Till Stress Do Us Part.

A growing body of evidence demonstrates a significant relationship between cellular redox state and circadian rhythms. Each day these two vital components of plant biology influence one another, dictating the pace for metabolism and physiology. Diverse environmental stressors can disrupt this condition and, although plant scientists have made significant progress in re-constructing functional networks of plant stress responses, stress impacts on the clock-redox crosstalk is poorly understood.

Mapping and Predicting Non-Linear Growth Phenotypes Based on Bayesian and Frequentist Complex Trait Estimation.

Predicting phenotypes based on genotypes and understanding the effects of complex multi-locus traits on plant performance requires a description of the underlying developmental processes, growth trajectories, and their genomic architecture. Using data from genotypes grown in multiple density settings and seasons, we applied a hierarchical Bayesian Function-Valued Trait (FVT) approach to fit logistic growth curves to leaf phenotypic data (length and width) and characterize leaf development. We found evidence of genetic variation in phenotypic plasticity of rate and duration of leaf growth to growing season.