Ancient oak's youthful genome surprises biologists

Not all mutations have a phenotypic effect that can be selected against. The interesting part of this study is that there is (apparently) a lack of mutations in non-coding regions.

There's also the (recently) obvious correlation between length of life and genetic integrity.

> First of all we have access to less than half of this organism only. What about root mutations?

The study specifically examined the issue of mutations arising in the cell line from zygote to terminal branches, since that is where reproduction takes place and we are most interested in mutations that are passed from one generation to the next. If stem cells at the root tips show more mutations, so what? The authors established (pending peer-review) a surprisingly low rate for this particular sequence, that's sufficiently interesting in itself.

> And second, we have accces only to the 'bad half' in our search for mutations...

"Sixteen of the 17 SNVs identified in the Napoleon Oak occurred in introns or non-coding sequences that are probably neutral... These results... demonstrate [the mutations'] gradual, nested appearance and fixation in developmentally connected branches during the growth of the oak tree. Thus, while the exact ontogeny of the Napoleon Oak may be difficult to reconstruct, our SNV analysis generated nested set of lineages supported by derived mutations"

They sampled across many independent cell lineages and across noncoding regions, and they are looking specifically at mutation rates in the cell line that leads to gamete formation. The kind of mutational "auto-cleaning" you describe is mostly just your unsubstantiated thinking about growth-related phenomena that are actually explained by a host of non-mutational factors; in any case undersampling due to rare deleterious mutation self-pruning would not have a confounding effect on the results here.

>There is not need here of a genetic mechanism to protect cells from mutations.

Just because trees can tolerate certain kinds of pathogen and insect-induced tumors doesn't mean they are entirely without need of protecting genome sequence integrity. Plants like other organisms do have sophisticated mechanisms to repair and maintain DNA, this becomes especially important in the stem cell lines leading to reproduction. The study shows these mechanisms in this oak are particularly efficient.