Molecular approaches to understanding auxin action.

The plant hormone auxin is thought to be involved in diverse growth and developmental processes. The mechanisms by which the hormone exerts its effects are unknown. Recent evidence suggests that auxin can rapidly and specifically alter the expression of a select set of mRNAs. Auxin-responsive mRNAs from several plant systems have been isolated and characterized and, in a few cases, the corresponding gene sequence and organization have been elucidated. The rapid accumulation of auxin-responsive mRNAs appears to be regulated at both the transcriptional and post-transcriptional levels. Research efforts are currently focused on elucidating the cis-acting elements and trans-acting factors that mediate the regulation of genes by auxin. Additionally, the function of the auxin-responsive gene products and their relationship, if any, to auxin-regulated growth processes remain to be determined.