Cell morphogenesis: How plants split hairs

How is shape controlled at the level of the smallest unit of an organism — the individual cell? A powerful system for addressing this question in plants is provided by the leaf trichomes of the model plant Arabidopsis thaliana [1,2]. Trichomes are unicellular hairs originating from epidermal cells (Figure 1a), which are up to 500 μm long and 50 μm wide at their base, and contain sixteen times more DNA than diploid cells — their genomic DNA content is thus ‘32C’ rather than the usual ‘2C’. The process of trichome morphogenesis has proved well suited to genetic dissection, and recent studies, including the identification of new mutants with abnormal trichomes and analysis of the cytoskeleton, have led to a new view of how trichome morphogenesis might be controlled.