RESUMEN
The oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC), known as oxi-mCs, garners significant interest in plants as potential epigenetic marks. While research in mammals has established a role in cell reprogramming, carcinogenesis and gene regulation, their functions in plants remain unclear. In rice, 5hmC has been associated with transposable elements and heterochromatin. This study utilizes Silene latifolia, a dioecious plant with heteromorphic sex chromosomes and a genome with a large proportion of transposable elements, which provides a favourable environment for the study of oxi-mCs in individual sexes. Notably, we detected surprisingly high levels of oxi-mCs in S. latifolia comparable to mammals. Nuclei showed enrichment in heterochromatic regions, except for 5hmC which signal was homogeneously distributed. Intriguingly, the same X chromosome in females displayed overall enrichment of 5hmC and 5fC regarding its counterpart. This fact is shared with 5mC resembling dosage compensation. Colocalization showed higher correlation between 5mC and 5fC than with 5hmC, suggesting no potential relationship between 5hmC and 5fC. Additionally, the promoter of several sex-linked genes and sex biased TEs gathered on a clear sex-dependent clustering. Together, these findings unveil a hypothetical role of oxi-mCs in S. latifolia sex chromosome development, warranting further exploration.
RESUMEN
Introduction: Plants undergo various natural changes that dramatically modify their genomes. One is polyploidization and the second is hybridization. Both are regarded as key factors in plant evolution and result in phenotypic differences in different plant organs. In Silene, we can find both examples in nature, and this genus has a seed shape diversity that has long been recognized as a valuable source of information for infrageneric classification. Methods: Morphometric analysis is a statistical study of shape and size and their covariations with other variables. Traditionally, seed shape description was limited to an approximate comparison with geometric figures (rounded, globular, reniform, or heart-shaped). Seed shape quantification has been based on direct measurements, such as area, perimeter, length, and width, narrowing statistical analysis. We used seed images and processed them to obtain silhouettes. We performed geometric morphometric analyses, such as similarity to geometric models and elliptic Fourier analysis, to study the hybrid offspring of S. latifolia and S. dioica. Results: We generated synthetic tetraploids of Silene latifolia and performed controlled crosses between diploid S. latifolia and Silene dioica to analyze seed morphology. After imaging capture and post-processing, statistical analysis revealed differences in seed size, but not in shape, between S. latifolia diploids and tetraploids, as well as some differences in shape among the parentals and hybrids. A detailed inspection using fluorescence microscopy allowed for the identification of shape differences in the cells of the seed coat. In the case of hybrids, differences were found in circularity and solidity. Overal seed shape is maternally regulated for both species, whereas cell shape cannot be associated with any of the sexes. Discussion: Our results provide additional tools useful for the combination of morphology with genetics, ecology or taxonomy. Seed shape is a robust indicator that can be used as a complementary tool for the genetic and phylogenetic analyses of Silene hybrid populations.
