Role of HEMIVENATA and the Ubiquitin Pathway in Venation Pattern Formation.

Elegant work by others has highlighted the importance of auxin transport in venation patterning, an idea substantiated by the severe effects of auxin polar transport inhibitors and by the mutant phenotype and expression patterns associated with the auxin efflux transporter PIN-FORMED1 (PIN1). It is striking, therefore, that little attention has been paid to the venation patterns of mutants insensitive to this hormone, since both auxin transport and perception are crucial components in theoretical models of vascular patterning. Our finding that HEMIVENATA (HVE) is the same gene as CAND1 confirms the role of ubiquitin-mediated auxin perception in vascular patterning and sets the stage for a re-examination of the leaf venation phenotypes of other auxin-resistant mutants and additional components of the ubiquitin pathway.