Palindromic Sequence-Targeted (PST) PCR, Version 2: An Advanced Method for High-Throughput Targeted Gene Characterization and Transposon Display

Genetic Polymorphism in the Amaranthaceae Species in the Context of Stress Tolerance

The adaptive potential and biochemical properties of the Amaranthaceae species make them promising for introduction into agriculture and markets, particularly in arid conditions. Molecular genetic polymorphism analysis is the most powerful tool for studying plant resources; therefore, the current study aimed to investigate the polymorphisms of allelic variations in the ARF and SOD gene families, as well as the genetic diversity of six Amaranthaceae species, using retrotransposon-based fingerprinting with the multi-locus EPIC-PCR profiling approach. Additionally, the iPBS PCR amplification was employed for genome profiling, revealing variations in genetic diversity among the studied Amaranthaceae samples. The observed genetic diversity in Amaranthaceae species contributes to their enhanced tolerance to adverse environmental conditions. The knowledge about the genetic diversity of genes crucial in plant development and stress resistance can be useful for the genetic improvement of cultivated Amaranthaceae species.

Identification of T-DNA structure and insertion site in transgenic crops using targeted capture sequencing

The commercialization of GE crops requires a rigorous safety assessment, which includes a precise DNA level characterization of inserted T-DNA. In the past, several strategies have been developed for identifying T-DNA insertion sites including, Southern blot and different PCR-based methods. However, these methods are often challenging to scale up for screening of dozens of transgenic events and for crops with complex genomes, like potato. Here, we report using target capture sequencing (TCS) to characterize the T-DNA structure and insertion sites of 34 transgenic events in potato. This T-DNA is an 18 kb fragment between left and right borders and carries three resistance (R) genes (RB, Rpi-blb2 and Rpi-vnt1.1 genes) that result in complete resistance to late blight disease. Using TCS, we obtained a high sequence read coverage within the T-DNA and junction regions. We identified the T-DNA breakpoints on either ends for 85% of the transgenic events. About 74% of the transgenic events had their T-DNA with 3R gene sequences intact. The flanking sequences of the T-DNA were from the potato genome for half of the transgenic events, and about a third (11) of the transgenic events have a single T-DNA insertion mapped into the potato genome, of which five events do not interrupt an existing potato gene. The TCS results were confirmed using PCR and Sanger sequencing for 6 of the best transgenic events representing 20% of the transgenic events suitable for regulatory approval. These results demonstrate the wide applicability of TCS for the precise T-DNA insertion characterization in transgenic crops.

The power of retrotransposons in high-throughput genotyping and sequencing

The use of molecular markers has become an essential part of molecular genetics through their application in numerous fields, which includes identification of genes associated with targeted traits, operation of backcrossing programs, modern plant breeding, genetic characterization, and marker-assisted selection. Transposable elements are a core component of all eukaryotic genomes, making them suitable as molecular markers. Most of the large plant genomes consist primarily of transposable elements; variations in their abundance contribute to most of the variation in genome size. Retrotransposons are widely present throughout plant genomes, and replicative transposition enables them to insert into the genome without removing the original elements. Various applications of molecular markers have been developed that exploit the fact that these genetic elements are present everywhere and their ability to stably integrate into dispersed chromosomal localities that are polymorphic within a species. The ongoing development of molecular marker technologies is directly related to the deployment of high-throughput genotype sequencing platforms, and this research is of considerable significance. In this review, the practical application to molecular markers, which is a use of technology of interspersed repeats in the plant genome were examined using genomic sources from the past to the present. Prospects and possibilities are also presented.

Genetic Diversity in Natural Populations of Rhodiola Species of Different Adaptation Strategies

Representatives of the Crassulaceae family’s genus Rhodiola are succulents, making them distinctive in a changing environment. One of the most significant tools for analyzing plant resources, including numerous genetic processes in wild populations, is the analysis of molecular genetic polymorphism. This work aimed to look at the polymorphisms of allelic variations of the superoxide dismutase (SOD) and auxin response factor (ARF) gene families, as well as the genetic diversity of five Rhodiola species, using the retrotransposons-based fingerprinting approach. The multi-locus exon-primed intron-crossing (EPIC-PCR) profiling approach was used to examine allelic variations in the SOD and ARF gene families. We implemented the inter-primer binding site (iPBS) PCR amplification technique for genome profiling, which demonstrated a significant level of polymorphism in the Rhodiola samples studied. Natural populations of Rhodiola species have a great capacity for adaptation to unfavorable environmental influences. The genetic variety of wild populations of Rhodiola species leads to their improved tolerance of opposing environmental circumstances and species evolutionary divergence based on the diversity of reproductive systems.

A review of strategies used to identify transposition events in plant genomes

Transposable elements (TEs) were initially considered redundant and dubbed 'junk DNA'. However, more recently they were recognized as an essential element of genome plasticity. In nature, they frequently become active upon exposition of the host to stress conditions. Even though most transposition events are neutral or even deleterious, occasionally they may happen to be beneficial, resulting in genetic novelty providing better fitness to the host. Hence, TE mobilization may promote adaptability and, in the long run, act as a significant evolutionary force. There are many examples of TE insertions resulting in increased tolerance to stresses or in novel features of crops which are appealing to the consumer. Possibly, TE-driven de novo variability could be utilized for crop improvement. However, in order to systematically study the mechanisms of TE/host interactions, it is necessary to have suitable tools to globally monitor any ongoing TE mobilization. With the development of novel potent technologies, new high-throughput strategies for studying TE dynamics are emerging. Here, we present currently available methods applied to monitor the activity of TEs in plants. We divide them on the basis of their operational principles, the position of target molecules in the process of transposition and their ability to capture real cases of actively transposing elements. Their possible theoretical and practical drawbacks are also discussed. Finally, conceivable strategies and combinations of methods resulting in an improved performance are proposed.

High-throughput detection of T-DNA insertion sites for multiple transgenes in complex genomes

BACKGROUND

Genetic engineering of crop plants has been successful in transferring traits into elite lines beyond what can be achieved with breeding techniques. Introduction of transgenes originating from other species has conferred resistance to biotic and abiotic stresses, increased efficiency, and modified developmental programs. The next challenge is now to combine multiple transgenes into elite varieties via gene stacking to combine traits. Generating stable homozygous lines with multiple transgenes requires selection of segregating generations which is time consuming and labor intensive, especially if the crop is polyploid. Insertion site effects and transgene copy number are important metrics for commercialization and trait efficiency.

RESULTS

We have developed a simple method to identify the sites of transgene insertions using T-DNA-specific primers and high-throughput sequencing that enables identification of multiple insertion sites in the T₁ generation of any crop transformed via Agrobacterium. We present an example using the allohexaploid oil-seed plant Camelina sativa to determine insertion site location of two transgenes.

CONCLUSION

This new methodology enables the early selection of desirable transgene location and copy number to generate homozygous lines within two generations.

Primer Binding Site (PBS) Profiling of Genetic Diversity of Natural Populations of Endemic Species Allium ledebourianum Schult

Endemic species are especially vulnerable to biodiversity loss caused by isolation or habitat specificity, small population size, and anthropogenic factors. Endemic species biodiversity analysis has a critically important global value for the development of conservation strategies. The rare onion Allium ledebourianum is a narrow-lined endemic species, with natural populations located in the extreme climatic conditions of the Kazakh Altai. A. ledebourianum populations are decreasing everywhere due to anthropogenic impact, and therefore, this species requires preservation and protection. Conservation of this rare species is associated with monitoring studies to investigate the genetic diversity of natural populations. Fundamental components of eukaryote genome include multiple classes of interspersed repeats. Various PCR-based DNA fingerprinting methods are used to detect chromosomal changes related to recombination processes of these interspersed elements. These methods are based on interspersed repeat sequences and are an effective approach for assessing the biological diversity of plants and their variability. We applied DNA profiling approaches based on conservative sequences of interspersed repeats to assess the genetic diversity of natural A. ledebourianum populations located in the territory of Kazakhstan Altai. The analysis of natural A. ledebourianum populations, carried out using the DNA profiling approach, allowed the effective differentiation of the populations and assessment of their genetic diversity. We used conservative sequences of tRNA primer binding sites (PBS) of the long-terminal repeat (LTR) retrotransposons as PCR primers. Amplification using the three most effective PBS primers generated 628 PCR amplicons, with an average of 209 amplicons. The average polymorphism level varied from 34% to 40% for all studied samples. Resolution analysis of the PBS primers showed all of them to have high or medium polymorphism levels, which varied from 0.763 to 0.965. Results of the molecular analysis of variance showed that the general biodiversity of A. ledebourianum populations is due to interpopulation (67%) and intrapopulation (33%) differences. The revealed genetic diversity was higher in the most distant population of A. ledebourianum LD64, located on the Sarymsakty ridge of Southern Altai. This is the first genetic diversity study of the endemic species A. ledebourianum using DNA profiling approaches. This work allowed us to collect new genetic data on the structure of A. ledebourianum populations in the Altai for subsequent development of preservation strategies to enhance the reproduction of this relict species. The results will be useful for the conservation and exploitation of this species, serving as the basis for further studies of its evolution and ecology.