Rapid change of growth

The prominent and evolutionarily ancient role of the plant hormone auxin is the regulation of cell expansion. This expansion requires ordered arrangement of the cytoskeleton. But the molecular mechanisms underlying its regulation by signaling molecules including auxin are unknown. In a Nature paper (doi:10.1038/nature13889) published this week IST Austria professors Jiři Friml and Eva Benková together with collaborators offer an explanation for the interaction between auxin and the rapid re-orientation of microtubules.

Using the model plant Arabidopsis thaliana the researchers show that exogenous application of auxin or redistribution of endogenous auxin induces very rapid microtubule re-orientation from transverse to longitudinal within minutes, coherent with the inhibition of cell expansion. This fast auxin effect requires a specific auxin receptor Auxin Binding Protein 1 and involves a contribution of downstream signalling components. These components are required for the rapid re-orientation of microtubules to regulate cell elongation in roots and dark-grown hypocotyls as well as asymmetric growth during gravitropic responses.

The observations on the rapid regulation of microtubule arrangement provide insight into the long-sought molecular mechanism by which a major plant hormone exerts its fast effect on plant cell growth.