Vascular patterning: More than just auxin? Curr Biol 13: R485–R487

The plant hormone auxin has long been known to play a pivotal role in vascular patterning and differentiation. But auxin is not the whole story: recent genetic analyses have identified additional factors required for vascular patterning, one of them involving sterols. Plants exhibit characteristic vascular patterns in the stem and in leaves [1,2]. A large body of evidence points to the growth regulator auxin having a central role in vascular patterning [3-5]. But a number of recently described mutants with defective vascular pat-terning do not exhibit obvious defects related to auxin [6,7]. Do these mutants reveal patterning mechanisms that are independent of auxin function? During plant development, auxin induces th