Stem anatomy supports Arabidopsis thaliana as a model for insular woodiness

The soc1 ful double mutant of A. thaliana produced substantial secondary growth throughout all aboveground stems, whereas in the Col accession only a few cell layers of wood were produced at the base of old stems. This increased wood formation may be linked to inactivation of the flowering time genes SOC1 and FUL (Melzer et al., 2008). These two genes could play a crucial regulatory role in triggering genetic mechanisms that lead to insular woodiness outside A. thaliana, and this ‘simple’ two-gene loss could explain why many nonrelated herbaceous families have independently evolved into woody insular lineages throughout the world. However, SOC1 and FUL might not be the only suppressors of cambium formation; other upstream, downstream or parallel-acting (positive or negative) regulators could be even more important. Therefore, it is evident that many missing pieces of this intriguing genetic puzzle leading to insular woodiness in eudicots need to be found before we can better understand one of the most fascinating developmental aspects of plants (cf. Lev-Yadun, 1994; Chaffey et al., 2002; Nieminen et al., 2004).