XVI International Botanical Congess

Mechanisms underlying vascular tissue continuity are not known, but auxin signals have been implicated in vascular strand formation. We have analyzed responses of plant vascular systems to auxin transport inhibition and characterized relevant genes.Auxin transport appears to be essential for the formation of narrow continuous strands and in leaf primordia successive stages can be defined that are critical for the formation of different vein classes. Mutations in the Arabidopsis gene MP interfere with vascular continuity and the MP product is highly related to Auxin Response Factor 1 (ARF1) and other ARF genes. In organ development, MP is initially expressed in broad domains that become confined towards the vascular tissues. These observations support a role of the MP gene in relaying auxin signals in vascular development.