Structure of the Natural Transgene PgiC2 in the Common Grass Festuca ovina

BACKGROUND: A horizontal gene transfer has brought an active nuclear gene, PgiC2, from a polyploid Poa species (P. palustris or a close relative) into the common grass sheep's fescue (Festuca ovina). The donor and the receptor species are strictly reproductively separated, and PgiC2 occurs in a polymorphic state within F. ovina. The active gene copy is normally closely linked to a very similar pseudogene. METHODOLOGY/PRINCIPAL FINDINGS: By genome walking we have obtained the up- and downstream sequences of PgiC2 and of corresponding genes in the donor and recipient species. Comparisons of these sequences show that the complete upstream region necessary for the gene's expression is included in the transferred segment. About 1 kb upstream of PgiC2 a fragment with transposition associated properties has been found (TAF). It is present in P. palustris and its polyploid relatives, though not at the homologous position, and is absent from many other grasses, including non-transgenic F. ovina plants. It is possible that it is a part of a transposing element involved in getting the gene into a transferring agent and/or into the recipient chromosome. CONCLUSIONS/SIGNIFICANCE: The close similarity of the up- and downstream regions with the corresponding regions in P. palustris excludes all suggestions that PgiC2 is not a HGT but the result of a duplication within the F. ovina lineage. The small size of the genetic material transferred, the complex nature of the PgiC2 locus, and the associated fragment with transposition associated properties suggest that the horizontal transfer occurred via a vector and not via illegitimate pollination

Phenocave: An Automated, Standalone, and Affordable Phenotyping System for Controlled Growth Conditions

Controlled plant growth facilities provide the possibility to alter climate conditions affecting plant growth, such as humidity, temperature, and light, allowing a better understanding of plant responses to abiotic and biotic stresses. A bottleneck, however, is measuring various aspects of plant growth regularly and non-destructively. Although several high-throughput phenotyping facilities have been built worldwide, further development is required for smaller custom-made affordable systems for specific needs. Hence, the main objective of this study was to develop an affordable, standalone and automated phenotyping system called "Phenocave" for controlled growth facilities. The system can be equipped with consumer-grade digital cameras and multispectral cameras for imaging from the top view. The cameras are mounted on a gantry with two linear actuators enabling XY motion, thereby enabling imaging of the entire area of Phenocave. A blueprint for constructing such a system is presented and is evaluated with two case studies using wheat and sugar beet as model plants. The wheat plants were treated with different irrigation regimes or high nitrogen application at different developmental stages affecting their biomass accumulation and growth rate. A significant correlation was observed between conventional measurements and digital biomass at different time points. Post-harvest analysis of grain protein content and composition corresponded well with those of previous studies. The results from the sugar beet study revealed that seed treatment(s) before germination influences germination rates. Phenocave enables automated phenotyping of plants under controlled conditions, and the protocols and results from this study will allow others to build similar systems with dimensions suitable for their custom needs

Evidence for magnesium-phosphorus synergism and co-limitation of grain yield in wheat agriculture

Modern crop production is characterized by high nitrogen (N) application rates, which can influence the co-limitation of harvested yield by other nutrients. Using a multidimensional niche volume concept and scaling exponents frequently applied in plant ecological research, we report that increased N and phosphorus (P) uptake in a growing wheat crop along with enhanced grain biomass is associated with more than proportional increase of other nutrients. Furthermore, N conversion efficiency and grain yield are strongly affected by the magnesium (Mg) to P ratio in the growing crop. We analyzed a field trial in Central Sweden including nine wheat varieties grown during two years with contrasting weather, and found evidence for Mg co-limitation at lower grain yields and P co-limitation at higher yields. We argue that critical concentrations of single nutrients, which are often applied in agronomy, should be replaced by nutrient ratios. In addition, links between plant P and Mg contents and root traits were found; high root number enhanced the P:N ratio, whilst steep root angle, indicating deep roots, increased the Mg:N ratio. The results have significant implications on the management and breeding targets of agriculturally grown wheat, which is one of the most important food crops worldwide

A transnational and holistic breeding approach is needed for sustainable wheat production in the Baltic Sea region

The Baltic Sea is one of the largest brackish water bodies in the world. Eutrophication is a major concern in the Baltic Sea due to the leakage of nutrients to the sea with agriculture being the primary source. Wheat (Triticum aestivum L.) is the most widely grown crop in the countries surrounding the Baltic Sea and thus promoting sustainable agriculture practices for wheat cultivation will have a major impact on reducing pollution in the Baltic Sea. This approach requires identifying and addressing key challenges for sustainable wheat production in the region. Implementing new technologies for climate-friendly breeding and digital farming across all surrounding countries should promote sustainable intensification of agriculture in the region. In this review, we highlight major challenges for wheat cultivation in the Baltic Sea region and discuss various solutions integrating transnational collaboration for pre-breeding and technology sharing to accelerate development of low input wheat cultivars with improved host plant resistance to pathogen and enhanced adaptability to the changing climate.Peer reviewe

Horizontal gene transfer in plants - The story of PgiC2

Sheep's fescue, Festuca ovina, is a common grass found all over Eurasia. In populations in southern Sweden some individuals were found to have two copies of the gene for cytoplasmic phosphoglucose isomerase, PgiC. The second copy, PgiC2, was first believed to be a duplicate of the original gene, PgiC1, but comparisons showed that this is not probable. The PgiC2 locus comprises two PgiC2 genes that may be fully functional genes or inactive pseudogenes. Phylogenetic analyses based on PgiC sequences from several grasses show that PgiC1 clusters with sequences from other fine-leaved festucoids and that PgiC2 clusters with a group of polyploid Poa species. Thus, PgiC2 has its most likely origin among the Poas, and it is particularly similar to a sequence from P. palustris. The estimated time of transfer is less than 600 000 years ago. We have discovered that the PgiC2 locus is not a local phenomenon, but that it can be found in several populations around the Baltic region. Most notable is a population from Poland where 50% of the plants are transgenic. Studies of the up- and downstream flanking regions of the PgiC2 gene have been conducted. Sequences from PgiC1 and PgiC2 can be aligned for approximately 660 bp upstream of the gene; as PgiC2 is fully functional, these 660 bp probably contain all elements necessary for gene regulation and function. PgiC2 and PgiC from P. palustris can align for another 110 bp. Beyond the breakpoint of PgiC2 and PgiC from P. palustris there is a 145 bp long fragment we call the transgene characteristic fragment (TCF). Primers constructed to amplify this fragment generate a product when used on transgenic F. ovina plants, but not when F. ovina plants without PgiC2 are probed. Thus, it seems as if the TCF is specifically associated with the PgiC2 locus. Interestingly, when the same primers are used on the polyploid Poa species closest to PgiC2 in the phylogenetic analyses, a PCR product is generated even though the fragment must be positioned beyond the breakpoint between PgiC2 and PgiC in P. palustris. This could indicate that TCF is part of a transposable element present in the polyploid Poa species and that its localization close to PgiC2 in F. ovina is not coincidental. This element may have contributed to the transfer of PgiC2 into F. ovina

Impacts of heat, drought, and combined heat-drought stress on yield, phenotypic traits, and gluten protein traits: capturing stability of spring wheat in excessive environments

Wheat production and end-use quality are severely threatened by drought and heat stresses. This study evaluated stress impacts on phenotypic and gluten protein characteristics of eight spring wheat genotypes (Diskett, Happy, Bumble, SW1, SW2, SW3, SW4, and SW5) grown to maturity under controlled conditions (Biotron) using RGB imaging and size-exclusion high-performance liquid chromatography (SE-HPLC). Among the stress treatments compared, combined heat-drought stress had the most severe negative impacts on biomass (real and digital), grain yield, and thousand kernel weight. Conversely, it had a positive effect on most gluten parameters evaluated by SE-HPLC and resulted in a positive correlation between spike traits and gluten strength, expressed as unextractable gluten polymer (%UPP) and large monomeric protein (%LUMP). The best performing genotypes in terms of stability were Happy, Diskett, SW1, and SW2, which should be further explored as attractive breeding material for developing climate-resistant genotypes with improved bread-making quality. RGB imaging in combination with gluten protein screening by SE-HPLC could thus be a valuable approach for identifying climate stress-tolerant wheat genotypes

Geographic and molecular variation in a natural plant transgene.

A PCR based survey of Festuca ovina plants from populations around the southern part of the Baltic Sea demonstrates both geographic and molecular variation in the enzyme gene PgiC2, horizontally transferred from a Poa-species. Our results show that PgiC2-a natural functional nuclear transgene-is not a local ephemeral phenomenon but is present in a very large number of individuals. We find also that its frequency is geographically variable and that it appears in more than one molecular form. The chloroplast variation in the region does not indicate any distinct subdivision due to different colonization routes after the last glaciation. Our data illustrate the geographic and molecular variation that may occur in natural populations with a polymorphic, unfixed transgene affected by diverse kinds of mutational and evolutionary processes

Striving for Stability in the Dough Mixing Quality of Spring Wheat under the Influence of Prolonged Heat and Drought

The effects of prolonged heat and drought stress and cool growing conditions on dough mixing quality traits of spring wheat (Triticum aestivum L.) were studied in fifty-six genotypes grown in 2017 and 2018 in southern Sweden. The mixing parameters evaluated by mixograph and the gluten protein characteristics studied by size exclusion high-performance liquid chromatography (SE-HPLC) in dough were compared between the two growing seasons which were very different in length, temperature and precipitation. The genotypes varying in gluten strength between the growing seasons (≤5%, ≤12%, and ≤17%) from three groups (stable (S), moderately stable (MS), and of varying stability (VS)) were studied. The results indicate that most of the mixing parameters were more strongly impacted by the interaction between the group, genotype, and year than by their individual contribution. The excessive prolonged heat and drought did not impact the buildup and mixing time expressed as peak time and time 1–2. The gluten polymeric proteins (unextractable, %UPP; total unextractable, TOTU) and large unextractable monomeric proteins (%LUMP) were closely associated with buildup and water absorption in dough. Major significant differences were found in the dough mixing parameters between the years within each group. In Groups S and MS, the majority of genotypes showed the smallest variation in the dough mixing parameters responsible for the gluten strength and dough development between the years. The mixing parameters such as time 1–2, buildup, and peak time (which were not affected by prolonged heat and drought stress) together with the selected gluten protein parameters (%UPP, TOTU, and %LUMP) are essential components to be used in future screening of dough mixing quality in wheat in severe growing environments

Origin and timing of the horizontal transfer of a PgiC gene from Poa to Festuca ovina.

A segregating second locus, PgiC2, for the enzyme phosphoglucose isomerase (PGIC) is found in the grass sheep's fescue, Festuca ovina. We have earlier reported that a phylogenetic analysis indicates that PgiC2 has been horizontally transferred from the reproductively separated grass genus Poa. Here we extend our analysis to include intron and exon information on 27 PgiC sequences from 18 species representing five genera, and confirm our earlier finding. The origin of PgiC2 can be traced to a group of closely interrelated, polyploid and partially asexual Poa species. The sequence most similar to PgiC2 is found in Poa palustris with a divergence, based on synonymous substitutions, of only 0.67%. This value suggests that the transfer took place less than 600,000years ago (late Pleistocene), at a time when most extant Poa and Festuca species already existed

Impacts of heat, drought, and combined heat–drought stress on yield, phenotypic traits, and gluten protein traits: capturing stability of spring wheat in excessive environments

Wheat production and end-use quality are severely threatened by drought and heat stresses. This study evaluated stress impacts on phenotypic and gluten protein characteristics of eight spring wheat genotypes (Diskett, Happy, Bumble, SW1, SW2, SW3, SW4, and SW5) grown to maturity under controlled conditions (Biotron) using RGB imaging and size-exclusion high-performance liquid chromatography (SE-HPLC). Among the stress treatments compared, combined heat–drought stress had the most severe negative impacts on biomass (real and digital), grain yield, and thousand kernel weight. Conversely, it had a positive effect on most gluten parameters evaluated by SE-HPLC and resulted in a positive correlation between spike traits and gluten strength, expressed as unextractable gluten polymer (%UPP) and large monomeric protein (%LUMP). The best performing genotypes in terms of stability were Happy, Diskett, SW1, and SW2, which should be further explored as attractive breeding material for developing climate-resistant genotypes with improved bread-making quality. RGB imaging in combination with gluten protein screening by SE-HPLC could thus be a valuable approach for identifying climate stress–tolerant wheat genotypes