Identification and characterization of transposable element AhMITE1 in the genomes of cultivated and two wild peanuts

Identification of a New Major Oil Content QTL Overlapped with FAD2B in Cultivated Peanut (Arachis hypogaea L.)

High oil content in peanut seeds is a key breeding objective for peanut (Arachis hypogaea L.) quality improvement. In order to explore the genetic basis of oil content in peanuts, a recombinant inbred line (RIL) population consisting of 256 lines was phenotyped across six environments. Continuous distribution and transgressive segregation for both oil content and oleic acid content were demonstrated across all environments. Quantitative trait locus (QTL) analysis yielded 15 additive QTLs explaining 4.34 to 23.10% of phenotypic variations. A novel stable and major QTL region conditioning oil content (qOCB09.1) was mapped to chromosome B09, spanning a 1.99 Mb genomic region with 153 putative genes, including the oleic acid gene FAD2B, which may influence the oil content. Candidate genes were identified and diagnostic markers for this region were developed for further investigation. Additionally, 18 pairs of epistatic interactions involving 35 loci were identified to affect the oil content, explaining 1.25 to 1.84% of phenotypic variations. These findings provide valuable insights for further map-based cloning of favorable alleles for oil content in peanuts.

The Genomic Shock Hypothesis: Genetic and Epigenetic Alterations of Transposable Elements after Interspecific Hybridization in Plants

Transposable elements (TEs) are major components of plant genomes with the ability to change their position in the genome or to create new copies of themselves in other positions in the genome. These can cause gene disruption and large-scale genomic alterations, including inversions, deletions, and duplications. Host organisms have evolved a set of mechanisms to suppress TE activity and counter the threat that they pose to genome integrity. These includes the epigenetic silencing of TEs mediated by a process of RNA-directed DNA methylation (RdDM). In most cases, the silencing machinery is very efficient for the vast majority of TEs. However, there are specific circumstances in which TEs can evade such silencing mechanisms, for example, a variety of biotic and abiotic stresses or in vitro culture. Hybridization is also proposed as an inductor of TE proliferation. In fact, the discoverer of the transposons, Barbara McClintock, first hypothesized that interspecific hybridization provides a "genomic shock" that inhibits the TE control mechanisms leading to the mobilization of TEs. However, the studies carried out on this topic have yielded diverse results, showing in some cases a total absence of mobilization or being limited to only some TE families. Here, we review the current knowledge about the impact of interspecific hybridization on TEs in plants and the possible implications of changes in the epigenetic mechanisms.

Conserved structured domains in plant non-coding RNA enod40, their evolution and recruitment of sequences from transposable elements

Plant long noncoding RNA enod40 is involved in the regulation of symbiotic associations with bacteria, in particular, in nitrogen-fixing root nodules of legumes, and with fungi in phosphate-acquiring arbuscular mycorrhizae formed by various plants. The presence of enod40 genes in plants that do not form such symbioses indicates its other roles in cell physiology. The molecular mechanisms of enod40 RNA function are poorly understood. Enod40 RNAs form several structured domains, conserved to different extents. Due to relatively low sequence similarity, identification of enod40 sequences in plant genomes is not straightforward, and many enod40 genes remain unannotated even in complete genomes. Here, we used comparative structure analysis and sequence similarity searches in order to locate enod40 genes and determine enod40 RNA structures in nitrogen-fixing clade plants and in grasses. The structures combine conserved features with considerable diversity of structural elements, including insertions of structured domain modules originating from transposable elements. Remarkably, these insertions contain sequences similar to tandem repeats and several stem-loops are homologous to microRNA precursors.