Curr. Biol. http://dx.doi.org/10.1016/j.cub.2016.03.067 (2016)

Some plants live fast and die after only a few weeks, while several species of trees (such as the bristlecone pine) can survive for thousands of years. One of the problems faced by these long-lifespan individuals is the accumulation of deleterious somatic mutations in the absence of recombination (an effect known as Muller's ratchet), which leads ultimately to death. Agata Burian from the University of Bern and colleagues now show that plants use developmental strategies to delay this outcome.

Tracking cells by time-lapse imaging in Arabidopsis and tomato indicated that precursors to the axillary meristem (from which the lateral organs develop) are specified early and their mitotic activity is then inhibited. Cell lineage analysis revealed that 6between only seven and nine divisions are needed to form the axillary meristem from apical meristem — which is fewer than the number needed to produce fully differentiated cells. Extrapolating these results to trees, a computer model predicted that mutations occurring in meristematic stem cells would only affect a subset of branches, increasing genetic heterogeneity.

Considering a single tree as a clonal population of competing reiterative branches, such a distribution of mutations would slow down Muller's ratchet and enable a longer lifespan of the whole organism. Although longevity experiments are difficult to achieve, deep sequencing of old tree sectors could confirm this hypothesis experimentally.