Allopolyploidization increases genetic recombination in the ancestral diploid D genome during wheat evolution

Genetic recombination produces new allelic combinations,thereby introducing variation for domestication.Allopolyploidization has increased the evolutionary potential of hexaploid common wheat by conferring the advantages of heterosis and gene redundancy,but whether a relationship exists between allopolyploidization and genetic recombination is currently unknown.To study the impact of allopolyploid ization on genetic recombination in the ancestral D genome of wheat,we generated new synthetic hexaploid wheats by crossing tetraploid Triticum turgidum with multiple diploid Aegilops tauschii accessions,with subsequent chromosome doubling,to simulate the evolutionary hexaploidization process.Using the DArT-Seq approach,we determined the genotypes of two new synthetic hexaploid wheats with their parents,F;plants in a diploid population(2 x,D_(1)D_(1)×D_(2)D_(2))and its new synthetic hexaploid wheatderived population(6 x,AABBD_(1)D_(1)×AABBD_(2)D_(2)).About 11%of detected SNP loci spanning the D genome of Ae.tauschii were eliminated after allohexaploidization,and the degree of segregation distortion was increased in their hexaploid offspring from the F_(1) generation.Based on codominant genotypes,the mean genetic interval length and recombination frequency between pairs of adjacent and linked SNPs on D genome of the hexaploid F;population were 2.3 fold greater than those in the diploid F_(2) population,and the recombination frequency of Ae.tauschii was increased by their hexaploidization with T.turgidum.In conclusion,allopolyploidization increases genetic recombination of the ancestral diploid D genome of wheat,and DNA elimination and increased segregation distortion also occur after allopolyploidization.Increased genetic recombination could have produced more new allelic combinations subject to natural or artificial selection,helping wheat to spread rapidly to become a major global crop and thereby accelerating the evolution of wheat via hexaploidization.

Molecular Evolution of Protein Sequences and Codon Usage in Monkeypox Viruses

The monkeypox virus(mpox virus,MPXV)epidemic in 2022 has posed a significant public health risk.Yet,the evolutionary principles of MPXV remain largely unknown.Here,we examined the evolutionary patterns of protein sequences and codon usage in MPXV.We first demonstrated the signal of positive selection in OPG027,specifically in the CladeⅠlineage of MPXV.Subsequently,we discovered accelerated protein sequence evolution over time in the variants responsible for the 2022 outbreak.Furthermore,we showed strong epistasis between amino acid substitutions located in different genes.The codon adaptation index(CAI)analysis revealed that MPXV genes tended to use more non-preferred codons compared to human genes,and the CAI decreased over time and diverged between clades,with CladeⅠ>Ⅱa andⅡb-A>Ⅱb-B.While the decrease in fatality rate among the three groups aligned with the CAI pattern,it remains unclear whether this correlation was coincidental or if the deoptimization of codon usage in MPXV led to a reduction in fatality rates.This study sheds new light on the mechanisms that govern the evolution of MPXV in human populations.