A D-genome-originated Ty1/Copia-type retrotransposon family expanded significantly in tetraploid cottons

Targeted designing functional markers revealed the role of retrotransposon derived miRNAs as mobile epigenetic regulators in adaptation responses of pistachio

We developed novel miRNA-based markers based on salt responsive miRNA sequences to detect polymorphisms in miRNA sequences and locations. The validation of 76 combined miRNA + miRNA and miRNA + ISSR markers in the three extreme pistachio populations led to the identification of three selected markers that could link salt tolerance phenotype to genotype and divided pistachio genotypes and Pistacia species into three clusters. This novel functional marker system, in addition to more efficient performance, has higher polymorphisms than previous miRNA-based marker systems. The functional importance of the target gene of five miRNAs in the structure of the three selected markers in regulation of different genes such as ECA2, ALA10, PFK, PHT1;4, PTR3, KUP2, GRAS, TCP, bHLH, PHD finger, PLATZ and genes involved in developmental, signaling and biosynthetic processes shows that the polymorphism associated with these selected miRNAs can make a significant phenotypic difference between salt sensitive and tolerant pistachio genotypes. The sequencing results of selected bands showed the presence of conserved miRNAs in the structure of the mitochondrial genome. Further notable findings of this study are that the sequences of PCR products of two selected markers were annotated as Gypsy and Copia retrotransposable elements. The transposition of retrotransposons with related miRNAs by increasing the number of miRNA copies and changing their location between nuclear and organellar genomes can affect the regulatory activity of these molecules. These findings show the crucial role of retrotransposon-derived miRNAs as mobile epigenetic regulators between intracellular genomes in regulating salt stress responses as well as creating new and tolerant phenotypes for adaptation to environmental conditions.

Retrotransposons in Plant Genomes: Structure, Identification, and Classification through Bioinformatics and Machine Learning

Transposable elements (TEs) are genomic units able to move within the genome of virtually all organisms. Due to their natural repetitive numbers and their high structural diversity, the identification and classification of TEs remain a challenge in sequenced genomes. Although TEs were initially regarded as "junk DNA", it has been demonstrated that they play key roles in chromosome structures, gene expression, and regulation, as well as adaptation and evolution. A highly reliable annotation of these elements is, therefore, crucial to better understand genome functions and their evolution. To date, much bioinformatics software has been developed to address TE detection and classification processes, but many problematic aspects remain, such as the reliability, precision, and speed of the analyses. Machine learning and deep learning are algorithms that can make automatic predictions and decisions in a wide variety of scientific applications. They have been tested in bioinformatics and, more specifically for TEs, classification with encouraging results. In this review, we will discuss important aspects of TEs, such as their structure, importance in the evolution and architecture of the host, and their current classifications and nomenclatures. We will also address current methods and their limitations in identifying and classifying TEs.