I just looked at each of the papers you cite, and none of them support the claim of mRNA transfer between species. They talk about reverse transcription of RNAs in the same cell. (Which kingdoms - there are only three - are using mRNA for gene transfer?)
The last paper you cite shows that if you reverse transcribe a virus, you can get it to integrate into the genome, which is not very surprising, but it there is no evidence that this has happened in nature. And I have no doubt that people are checking - running PCR on genomic DNA of infected individuals.
The last paper you cite shows that if you reverse transcribe a virus, you can get it to integrate into the genome, which is not very surprising, but it there is no evidence that this has happened in nature. And I have no doubt that people are checking - running PCR on genomic DNA of infected individuals.