Identification of a major QTL that alters flowering time at elevated [CO(2)] in Arabidopsis thaliana

Quantitative Control of Early Flowering in White Lupin (Lupinus albus L.)

White lupin (Lupinus albus L.) is a pulse annual plant cultivated from the tropics to temperate regions for its high-protein grain as well as a cover crop or green manure. Wild populations are typically late flowering and have high vernalization requirements. Nevertheless, some early flowering and thermoneutral accessions were found in the Mediterranean basin. Recently, quantitative trait loci (QTLs) explaining flowering time variance were identified in bi-parental population mapping, however, phenotypic and genotypic diversity in the world collection has not been addressed yet. In this study, a diverse set of white lupin accessions (n = 160) was phenotyped for time to flowering in a controlled environment and genotyped with PCR-based markers (n = 50) tagging major QTLs and selected homologs of photoperiod and vernalization pathway genes. This survey highlighted quantitative control of flowering time in white lupin, providing statistically significant associations for all major QTLs and numerous regulatory genes, including white lupin homologs of CONSTANS, FLOWERING LOCUS T, FY, MOTHER OF FT AND TFL1, PHYTOCHROME INTERACTING FACTOR 4, SKI-INTERACTING PROTEIN 1, and VERNALIZATION INDEPENDENCE 3. This revealed the complexity of flowering control in white lupin, dispersed among numerous loci localized on several chromosomes, provided economic justification for future genome-wide association studies or genomic selection rather than relying on simple marker-assisted selection.

Impacts of CO2 elevation on the physiology and seed quality of soybean

Understanding the responses of crops to elevated atmospheric carbon dioxide concentrations (E[CO₂]) is very important in terms of global food supplies. The present study investigates the effects of CO₂ enrichment (to 800 μmol mol^-1) on the physiology of soybean plants and the nutritional value of their seeds under growth chamber conditions. The photosynthesis of soybean was significantly promoted by E[CO₂] at all growth stages, but leaf area and specific leaf weight were not affected. The levels of mineral elements in the leaves decreased under E[CO₂]. The soil properties after soybean cultivation under E[CO₂] were not affected, except for a decrease in available potassium. Moreover, the levels of soluble sugars in the seeds were not affected by E[CO₂], but the levels of natural antioxidants decreased. In addition, the level of oleic acid decreased under E[CO₂]. However, levels of fatty acid peroxidation and saturation were maintained. In conclusion, E[CO₂] appears to have positive effects on the growth of cultivated soybean plants, but its influence on the nutritional values of soybean seeds is complex.

Seed-Specific Gene MOTHER of FT and TFL1（MFT） Involved in Embryogenesis, Hormones and Stress Responses in Dimocarpus longan Lour

Mother of FT and TFL1 (MFT) belongs to phosphatidylethanolamine-binding protein (PEBP) family, which plays an important role in flowering time regulation, seed development, and germination. To gain insight into the molecular function of DlMFT in Dimocarpus longan Lour., we isolated DlMFT and its promoter sequence from longan embryogenic callus (EC). Bioinformatic analysis indicated that the promoter contained multiphytohormones and light responsive regulatory elements. Subcellular localization showed that the given the DlMFT signal localized in the nucleus, expression profiling implied that DlMFT showed significant upregulation during somatic embryogenesis (SE) and zygotic embryogenesis (ZE), and particular highly expressed in late or maturation stages. The accumulation of DlMFT was mainly detected in mature fruit and seed, while it was undetected in abortive seeds, and notably decreased during seed germination. DlMFT responded differentially to exogenous hormones in longan EC. Auxins, salicylic acid (SA) and methyl jasmonate (MeJa) suppressed its expression, however, abscisic acid (ABA), brassinosteroids (BR) showed the opposite function. Meanwhile, DlMFT differentially responded to various abiotic stresses. Our study revealed that DlMFT might be a key regulator of longan somatic and zygotic embryo development, and in seed germination, it is involved in complex plant hormones and abiotic stress signaling pathways.

Studying plant-pollinator interactions facing climate change and changing environments

Plant-pollinator interactions are essential for successful plant reproduction in both natural and agricultural systems. These interactions are negatively impacted by recent large-scale alterations of the environments, particularly climate change. The responses of plants and pollinators to changing abiotic conditions that vary seasonally and geographically are often uncoordinated, potentially leading to the breakdown of this interaction. The complexity of the responses of plants and pollinators to our changing climate necessitates creative approaches. The six articles in this special issue directly address this need by providing a variety of key methods and reviews of current methodology. The articles include: DNA barcoding methods for use on pollen collected from visiting bees; methods for assessment of plant attraction traits (nectar and review of floral volatiles methods); a field sampling method for ground nesting bees; a review of using spatial and temporal transplants for addressing changing dynamics of plant-pollinator interactions; and a review of approaches used to assess potential shifts in phenology of plants and pollinators. Collectively, these articles illustrate some of the breadth of approaches needed to address the changing dynamics of plant-pollinator interactions.

Integrating viability and fecundity selection to illuminate the adaptive nature of genetic clines

Genetically based trait variation across environmental gradients can reflect adaptation to local environments. However, natural populations that appear well-adapted often exhibit directional, not stabilizing, selection on ecologically relevant traits. Temporal variation in the direction of selection could lead to stabilizing selection across multiple episodes of selection, which might be overlooked in short-term studies that evaluate relationships of traits and fitness under only one set of conditions. Furthermore, nonrandom mortality prior to trait expression can bias inferences about trait evolution if viability selection opposes fecundity selection. Here, we leveraged fitness and trait data to test whether phenotypic clines are genetically based and adaptive, whether temporal variation in climate imposes stabilizing selection, and whether viability selection acts on adult phenotypes. We monitored transplants of the subalpine perennial forb, Boechera stricta (Brassicaceae), in common gardens at two elevations over 2-3 years that differed in drought intensity. We quantified viability, and fecundity fitness components for four heritable traits: specific leaf area, integrated water-use efficiency, height at first flower, and flowering phenology. Our results indicate that genetic clines are maintained by selection, but their expression is context dependent, as they do not emerge in all environments. Moreover, selection varied spatially and temporally. Stabilizing selection was most pronounced when we integrated data across years. Finally, viability selection prior to trait expression targeted adult phenotypes (age and size at flowering). Indeed, viability selection for delayed flowering opposed fecundity selection for accelerated flowering; this result demonstrates that neglecting to account for viability selection could lead to inaccurate conclusions that populations are maladapted. Our results suggest that reconciling clinal trait variation with selection requires data collected across multiple spatial scales, time frames, and life-history stages.

Examining Plant Physiological Responses to Climate Change through an Evolutionary Lens

Integrating knowledge from physiological ecology, evolutionary biology, phylogenetics, and paleobiology provides novel insights into factors driving plant physiological responses to both past and future climate change.

Implications of High Temperature and Elevated CO2 on Flowering Time in Plants

Flowering is a crucial determinant for plant reproductive success and seed-set. Increasing temperature and elevated carbon-dioxide (e[CO2]) are key climate change factors that could affect plant fitness and flowering related events. Addressing the effect of these environmental factors on flowering events such as time of day of anthesis (TOA) and flowering time (duration from germination till flowering) is critical to understand the adaptation of plants/crops to changing climate and is the major aim of this review. Increasing ambient temperature is the major climatic factor that advances flowering time in crops and other plants, with a modest effect of e[CO2].Integrated environmental stimuli such as photoperiod, temperature and e[CO2] regulating flowering time is discussed. The critical role of plant tissue temperature influencing TOA is highlighted and crop models need to substitute ambient air temperature with canopy or floral tissue temperature to improve predictions. A complex signaling network of flowering regulation with change in ambient temperature involving different transcription factors (PIF4, PIF5), flowering suppressors (HvODDSOC2, SVP, FLC) and autonomous pathway (FCA, FVE) genes, mainly from Arabidopsis, provides a promising avenue to improve our understanding of the dynamics of flowering time under changing climate. Elevated CO2 mediated changes in tissue sugar status and a direct [CO2]-driven regulatory pathway involving a key flowering gene, MOTHER OF FT AND TFL1 (MFT), are emerging evidence for the role of e[CO2] in flowering time regulation.

Genetic Architecture of Flowering Phenology in Cereals and Opportunities for Crop Improvement

Cereal crop species including bread wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), rice (Oryza sativa L.), and maize (Zea mays L.) provide the bulk of human nutrition and agricultural products for industrial use. These four cereals are central to meet future demands of food supply for an increasing world population under a changing climate. A prerequisite for cereal crop production is the transition from vegetative to reproductive and grain-filling phases starting with flower initiation, a key developmental switch tightly regulated in all flowering plants. Although studies in the dicotyledonous model plant Arabidopsis thaliana build the foundations of our current understanding of plant phenology genes and regulation, the availability of genome assemblies with high-confidence sequences for rice, maize, and more recently bread wheat and barley, now allow the identification of phenology-associated gene orthologs in monocots. Together with recent advances in next-generation sequencing technologies, QTL analysis, mutagenesis, complementation analysis, and RNA interference, many phenology genes have been functionally characterized in cereal crops and conserved as well as functionally divergent genes involved in flowering were found. Epigenetic and other molecular regulatory mechanisms that respond to environmental and endogenous triggers create an enormous plasticity in flowering behavior among cereal crops to ensure flowering is only induced under optimal conditions. In this review, we provide a summary of recent discoveries of flowering time regulators with an emphasis on four cereal crop species (bread wheat, barley, rice, and maize), in particular, crop-specific regulatory mechanisms and genes. In addition, pleiotropic effects on agronomically important traits such as grain yield, impact on adaptation to new growing environments and conditions, genetic sequence-based selection and targeted manipulation of phenology genes, as well as crop growth simulation models for predictive crop breeding, are discussed.

Plasticity in functional traits in the context of climate change: a case study of the subalpine forb Boechera stricta (Brassicaceae)

Environmental variation often induces shifts in functional traits, yet we know little about whether plasticity will reduce extinction risks under climate change. As climate change proceeds, phenotypic plasticity could enable species with limited dispersal capacity to persist in situ, and migrating populations of other species to establish in new sites at higher elevations or latitudes. Alternatively, climate change could induce maladaptive plasticity, reducing fitness, and potentially stalling adaptation and migration. Here, we quantified plasticity in life history, foliar morphology, and ecophysiology in Boechera stricta (Brassicaceae), a perennial forb native to the Rocky Mountains. In this region, warming winters are reducing snowpack and warming springs are advancing the timing of snow melt. We hypothesized that traits that were historically advantageous in hot and dry, low-elevation locations will be favored at higher elevation sites due to climate change. To test this hypothesis, we quantified trait variation in natural populations across an elevational gradient. We then estimated plasticity and genetic variation in common gardens at two elevations. Finally, we tested whether climatic manipulations induce plasticity, with the prediction that plants exposed to early snow removal would resemble individuals from lower elevation populations. In natural populations, foliar morphology and ecophysiology varied with elevation in the predicted directions. In the common gardens, trait plasticity was generally concordant with phenotypic clines from the natural populations. Experimental snow removal advanced flowering phenology by 7 days, which is similar in magnitude to flowering time shifts over 2-3 decades of climate change. Therefore, snow manipulations in this system can be used to predict eco-evolutionary responses to global change. Snow removal also altered foliar morphology, but in unexpected ways. Extensive plasticity could buffer against immediate fitness declines due to changing climates.

Natural variation in cross-talk between glucosinolates and onset of flowering in Arabidopsis

Naturally variable regulatory networks control different biological processes including reproduction and defense. This variation within regulatory networks enables plants to optimize defense and reproduction in different environments. In this study we investigate the ability of two enzyme-encoding genes in the glucosinolate pathway, AOP2 and AOP3, to affect glucosinolate accumulation and flowering time. We have introduced the two highly similar enzymes into two different AOP (null) accessions, Col-0 and Cph-0, and found that the genes differ in their ability to affect glucosinolate levels and flowering time across the accessions. This indicated that the different glucosinolates produced by AOP2 and AOP3 serve specific regulatory roles in controlling these phenotypes. While the changes in glucosinolate levels were similar in both accessions, the effect on flowering time was dependent on the genetic background pointing to natural variation in cross-talk between defense chemistry and onset of flowering. This variation likely reflects an adaptation to survival in different environments.

A synthetic framework for modeling the genetic basis of phenotypic plasticity and its costs

The phenotype of an individual is controlled not only by its genes, but also by the environment in which it grows. A growing body of evidence shows that the extent to which phenotypic changes are driven by the environment, known as phenotypic plasticity, is also under genetic control, but an overall picture of genetic variation for phenotypic plasticity remains elusive. Here, we develop a model for mapping quantitative trait loci (QTLs) that regulate environment-induced plastic response. This model enables geneticists to test whether there exist actual QTLs that determine phenotypic plasticity and, if there are, further test how plasticity QTLs control the costs of plastic response by dissecting the genetic correlation of phenotypic plasticity and trait value. The model was used to analyze real data for grain yield of winter wheat (Triticum aestivum), leading to the detection of pleiotropic QTLs and epistatic QTLs that affect phenotypic plasticity and its cost in this crop.