Karyotype and LTR-RTs analysis provide insights into oak genomic evolution

BACKGROUND

Whole-genome duplication and long terminal repeat retrotransposons (LTR-RTs) amplification in organisms are essential factors that affect speciation, local adaptation, and diversification of organisms. Understanding the karyotype projection and LTR-RTs amplification could contribute to untangling evolutionary history. This study compared the karyotype and LTR-RTs evolution in the genomes of eight oaks, a dominant lineage in Northern Hemisphere forests.

RESULTS

Karyotype projections showed that chromosomal evolution was relatively conservative in oaks, especially on chromosomes 1 and 7. Modern oak chromosomes formed through multiple fusions, fissions, and rearrangements after an ancestral triplication event. Species-specific chromosomal rearrangements revealed fragments preserved through natural selection and adaptive evolution. A total of 441,449 full-length LTR-RTs were identified from eight oak genomes, and the number of LTR-RTs for oaks from section Cyclobalanopsis was larger than in other sections. Recent amplification of the species-specific LTR-RTs lineages resulted in significant variation in the abundance and composition of LTR-RTs among oaks. The LTR-RTs insertion suppresses gene expression, and the suppressed intensity in gene regions was larger than in promoter regions. Some centromere and rearrangement regions indicated high-density peaks of LTR/Copia and LTR/Gypsy. Different centromeric regional repeat units (32, 78, 79 bp) were detected on different Q. glauca chromosomes.

CONCLUSION

Chromosome fusions and arm exchanges contribute to the formation of oak karyotypes. The composition and abundance of LTR-RTs are affected by its recent amplification. LTR-RTs random retrotransposition suppresses gene expression and is enriched in centromere and chromosomal rearrangement regions. This study provides novel insights into the evolutionary history of oak karyotypes and the organization, amplification, and function of LTR-RTs.

[Progress in clinical research of IgG4 related diseases in otology]

Summary Immunoglobulin G4-related disease is a systemic idiopathic inflammatory lesion.It is mainly characterized by infiltration of dense IgG4-positive plasma cells,typical storiform fibrosis,obliterative phlebitis and increased serum levels of IgG4.Patients with IgG4-related disease have frequently multiple organs involvement including structural damages of head and neck.But reports of temporal bone involvement in this kind of disease are rarely seen.This article reviews the recent progress in clinical research of lgG4-related disease in otology.

Improved biocompatibility of bovine pericardium using a new method of cross linking

The authors used glycerol (Gly) as a cross linking agent to treat bovine pericardium (BP) and compared it mechanically (tensile test) and biologically (subcutaneous implantation in rats) with glutaraldehyde (Glu) fixed lonescu-Shiley BP (ISBP). Maximum tensile stress (Stmax) was the same in both groups (n = 12 each), while maximum strain (Snmax) was larger in Gly BP. Calcium content (Ca) was lower and water content of tissue (WC) was higher in implants of Gly BP versus ISBP (n = 9 each). Gly BP appeared more hydrated than ISBP in specimens studied by scanning electron microscopy (SEM). In addition, SEM of three Gly BP mitral valves in sheep showed good growth of endothelial (En) cells. These biomechanical advantages of Gly BP over ISBP suggest that Gly may be a useful substitute for Glu in cross linking bovine pericardial valves.

Two-dimensional mechanical and ultrastructural correlates of bovine pericardium for prosthetic valves

Scanning electron microscopy of bovine pericardium (BP) shows anisotropic collagen fiber orientation (CFO). We studied the effect of CFO on the breaking strength of longitudinal (L) and transverse (T) strips cut from six pieces of fresh (Fr), glutaraldehyde (Glu)-, or formaldehyde (For)-fixed BP loaded at constant rate until rupture. Maximum tensile stress (Stmax) and strain (Snmax) were measured. The Stmax of L strips were larger than T ones in all groups, and Snmax was the same. Similar results were also observed in 10 pieces of Glu fixed normal canine mitral valves (MV). Maximum tensile stress is obtained when the load is parallel to CFO in both canine MV and BP.