Regulation of Plant Gene Expression by Auxins

Abstract

Application of the plant hormone auxin to intact plants, isolated plant parts, and cultured cells can have dramatic effects on subsequent growth and developmental processes (e.g., cell division, cell enlargement, cell differentiation, and organogenesis). It is generally believed that endogenous auxins play roles in plant growth and development similar to those observed when exogenous auxins are applied to plants or plant parts. Recent results from plants transformed with Agrobacterium tumefaciens auxin-biosynthetic genes supports the above contention (Klee et al., 1988). The mechanism(s) by which auxins affect plant growth and developmental processes is largely a mystery, but at least some of the processes are thought to involve changes in gene expression (Guilfoyle, 1986). In recent years, a number of cDNA clones for auxin-responsive mRNAs have been identified and characterized (Baulcombe and Key, 1980; Czarnecka et al., 1984; Hagen et al., 1984; McClure and Guilfoyle, 1987; Theologis et al., 1985; van der Zaal et al., 1987; Walker and Key, 1982). The genes encoding these mRNAs have also been identified in some cases (Ainley et al., 1988; Czarnecka et al., 1988; Hagen et al., 1988; McClure et al., 1989). Experiments to determine the functions of the auxin-responsive gene products and the signal transduction pathways involved in auxin-induced gene expression are only now being initiated. Here, we describe some the auxin-responsive mRNAs and genes that have been identified.