Identification of mutations in a temperature-sensitive mutant (tsm5) of murine cytomegalovirus using complementary genome sequencing

Edible and medicinal fungi breeding techniques, a review: Current status and future prospects

Mushrooms of the edible and medicinal which are highly nutritious and environmentally friendly crops carry numerous medicinal benefits. For the abundant and high diversity of bioactive metabolites they possess, which are considered to be an important pool of bioresources. The efficient breeding technique is always a challenging task in mushrooms for obtaining better character strains, which are essential for developing healthy products and even consumption. This review comprehensively summarizes the breeding techniques applied to the edible and medicinal mushrooms. Including the traditional mutagenesis method, and even modern gene-editing breeding techniques, the effects of each method, and the comparison of each breeding technique are systematic illustrations. Strategies for mushroom breeding techniques in the future are also discussed in this review paper. With the ongoing sequencing of the mushroom genome, knowledge of the gene background of the strains and functions can be available for developing better markers for gene-editing breeding as CRISPR/Cas9 systems. Combine the metabolism engineering and in-silico tools analysis was the rational design of the novel strains. Modern physical mutagenesis techniques such as the ARTP and the combination of the other physical, and chemical breeding mutagens with cross-breeding techniques or the protoplasts fusion will also lead to superior strains for cultivation and pave the way for higher quality and yield.

Lessons from studies with murine cytomegalovirus that could lead to a safe live attenuated vaccine for human cytomegalovirus

Studies with a murine cytomegalovirus mutant tsm5 suggested two possible approaches to producing a live attenuated human cytomegalovirus vaccine. One approach would be to use a combination of five to six mutants where an attenuating mutation in the gene of one mutant is compensated by the wild-type version in a second mutant, which in turn has a mutation in a different gene compensated by the wild-type version in a third mutant, etc. Important genes in this approach could include those involved in DNA replication. The importance of the carboxy terminase of the primase gene (M70/UL70) for its function suggested a second approach where some of the natural codons in this region could be substituted with synonymous non-preferred (minor) codons that would reduce the replication fitness of the mutant.

The genome of murine cytomegalovirus is shaped by purifying selection and extensive recombination

The herpesvirus lifestyle results in a long-term interaction between host and invading pathogen, resulting in exquisite adaptation of virus to host. We have sequenced the genomes of nine strains of murine cytomegalovirus (a betaherpesvirus), isolated from free-living mice trapped at locations separated geographically and temporally. Despite this separation these genomes were found to have low levels of nucleotide variation. Of the more than 160 open reading frames, almost 90% had a dN/dS ratio of amino acid substitutions of less than 0.6, indicating the level of purifying selection on the coding potential of MCMV. Examination of selection acting on individual genes at the codon level however indicates some level of positive selection, with 0.03% of codons showing strong evidence for positive selection. Conversely, 1.3% of codons show strong evidence of purifying selection. Alignments of both genome sequences and coding regions suggested that high levels of recombination have shaped the MCMV genome.