Browsing by Subject "LTR-RETROTRANSPOSONS"

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  • Voronova, Angelika; Rendón-Anaya, Martha; Ingvarsson, Pär; Kalendar, Ruslan; Ruņģis, Dainis (2020)
    Sequencing the giga-genomes of several pine species has enabled comparative genomic analyses of these outcrossing tree species. Previous studies have revealed the wide distribution and extraordinary diversity of transposable elements (TEs) that occupy the large intergenic spaces in conifer genomes. In this study, we analyzed the distribution of TEs in gene regions of the assembled genomes of Pinus taeda and Pinus lambertiana using high-performance computing resources. The quality of draft genomes and the genome annotation have significant consequences for the investigation of TEs and these aspects are discussed. Several TE families frequently inserted into genes or their flanks were identified in both species' genomes. Potentially important sequence motifs were identified in TEs that could bind additional regulatory factors, promoting gene network formation with faster or enhanced transcription initiation. Node genes that contain many TEs were observed in multiple potential transposable element-associated networks. This study demonstrated the increased accumulation of TEs in the introns of stress-responsive genes of pines and suggests the possibility of rewiring them into responsive networks and sub-networks interconnected with node genes containing multiple TEs. Many such regulatory influences could lead to the adaptive environmental response clines that are characteristic of naturally spread pine populations.
  • Li, Shitian; Ramakrishnan, Muthusamy; Vinod, K. K.; Kalendar, Ruslan; Yrjälä, Kim; Zhou, Mingbing (2020)
    Bamboo, a non-timber grass species, known for exceptionally fast growth, is a commercially viable crop. Long terminal repeat (LTR) retrotransposons, the main class I mobile genetic elements in plant genomes, are highly abundant (46%) in bamboo contributing to genome diversity. They play significant roles in the regulation of gene expression, chromosome size and structure as well as in genome integrity. Inter-retrotransposon amplified polymorphism (IRAP) is a high-throughput method to study the genetic diversity of plant species. Till date, there are no markers based on Transposable Elements (TEs) for the bamboo genome and no reports on bamboo genetic diversity using the IRAP method. Phyllostachys is an Asian bamboo, the largest group in the bamboo subfamily, Bambusoideae, and it is of great economic value due to its fast growth. The structure of LTR-retrotransposon superfamilies, Ty3-gypsy and Ty1-copia, were analysed in the bamboo genome using LTRharvest and LTRdigest software. A total of 98,850 LTR retrotransposons with both ends of intact LTR sequences were identified, grouped into 64,281 clusters/scaffolds, using CD-HIT software. Among the total of 64,281 clusters, 13 clusters had more than 30 copy numbers of LTR sequences and at least one copy had all intact protein domains such as gag protein and polyprotein. Based on the high copy numbers of conserved LTR sequences, a total of 16 IRAP primers were developed. All these IRAP primers were used to study the genetic diversity and population structure of the Asian bamboo. AMOVA analysis was done for 58 Asian bamboo species collected from nine different provinces of China, from Italy and America. In the bamboo species, these IRAP primers produced a total of 3340 amplicons with an average of 98% polymorphism. The 58 Asian bamboo species were grouped into two major clusters and four sub-clusters, based on UPGMA analysis. UPGMA cluster analysis was corroborated by statistical analyses of genetic similarity coefficients. Structure analysis showed that the bamboo species could be divided into four subpopulations (K = 4): SP1, SP2, SP3 and SP4. All SPs had an admixture of alleles. AMOVA analysis showed that higher genetic variations occurred within populations (75%) rather than among populations (25%). The study highlights the usability of IRAP in Asian bamboo to determine inter-species variability using retrotransposon markers.
  • Khapilina, Oxana; Raiser, Olesya; Danilova, Alevtina; Shevtsov, Vladislav; Turzhanova, Ainur; Kalendar, Ruslan (2021)
    Analysis of the genetic diversity of natural populations of threatened and endangered species of plants is a main aspect of conservation strategy. The endangered species Allium altaicum is a relict plant of the Ice Age and natural populations are located in extreme climatic conditions of Kazakstan's Altai Mountains. Mobile genetic elements and other interspersed repeats are basic components of a eukaryote genome, which can activate under stress conditions and indirectly promote the survival of an organism against environmental stresses. Detections of chromosomal changes related to recombination processes of mobile genetic elements are performed by various PCR methods. These methods are based on interspersed repeat sequences and are an effective tool for research of biological diversity of plants and their variability. In our research, we used conservative sequences of tRNA primer binding sites (PBS) when initializing the retrotransposon replication as PCR primers to research the genetic diversity of 12 natural populations of A. altaicum found in various ecogeographic conditions of the Kazakhstani Altai. High efficiency of the PBS amplification method used was observed already at the intrapopulation level. Unique amplicons representative of a certain population were found at the intrapopulation level. Analysis of molecular dispersion revealed that the biodiversity of populations of mountainous and lowland A. altaicum is due to intrapopulation differences for climatic zones of habitation. This is likely conditional upon predominance of vegetative reproduction over seed reproduction in some populations. In the case of vegetative reproduction, somatic recombination related to the activity of mobile genetic elements are preserved in subsequent generations. This leads to an increase of intrapopulation genetic diversity. Thus, high genetic diversity was observed in populations such as A. altaicum located in the territory of the Kalbinskii Altai, whereas the minimum diversity was observed in the populations of the Leninororsk ecogeographic group. Distinctions between these populations were also identified depending on the areas of their distribution. Low-land and mid-mountain living environments are characterized by a great variety of shapes and plasticity. This work allowed us to obtain new genetic data on the structure of A. altaicum populations on the territory of the Kazakhstan Altai for the subsequent development of preservation and reproduction strategies for this relict species.
  • Ramakrishnan, Muthusamy; Satish, Lakkakula; Kalendar, Ruslan; Mathiyazhagan, Narayanan; Sabariswaran, Kandasamy; Sharma, Anket; Emamverdian, Abolghassem; Wei, Qiang; Zhou, Mingbing (2021)
    Plant development processes are regulated by epigenetic alterations that shape nuclear structure, gene expression, and phenotypic plasticity; these alterations can provide the plant with protection from environmental stresses. During plant growth and development, these processes play a significant role in regulating gene expression to remodel chromatin structure. These epigenetic alterations are mainly regulated by transposable elements (TEs) whose abundance in plant genomes results in their interaction with genomes. Thus, TEs are the main source of epigenetic changes and form a substantial part of the plant genome. Furthermore, TEs can be activated under stress conditions, and activated elements cause mutagenic effects and substantial genetic variability. This introduces novel gene functions and structural variation in the insertion sites and primarily contributes to epigenetic modifications. Altogether, these modifications indirectly or directly provide the ability to withstand environmental stresses. In recent years, many studies have shown that TE methylation plays a major role in the evolution of the plant genome through epigenetic process that regulate gene imprinting, thereby upholding genome stability. The induced genetic rearrangements and insertions of mobile genetic elements in regions of active euchromatin contribute to genome alteration, leading to genomic stress. These TE-mediated epigenetic modifications lead to phenotypic diversity, genetic variation, and environmental stress tolerance. Thus, TE methylation is essential for plant evolution and stress adaptation, and TEs hold a relevant military position in the plant genome. High-throughput techniques have greatly advanced the understanding of TE-mediated gene expression and its associations with genome methylation and suggest that controlled mobilization of TEs could be used for crop breeding. However, development application in this area has been limited, and an integrated view of TE function and subsequent processes is lacking. In this review, we explore the enormous diversity and likely functions of the TE repertoire in adaptive evolution and discuss some recent examples of how TEs impact gene expression in plant development and stress adaptation.