Mechanisms of cross talk between gibberellin and other hormones.

It has always been clear that different plant hormones affect overlapping processes, such that the output of plant hormone action depends on specific hormone combinations rather than on the independent activities of each. In the last two decades, numerous components of the signal transduction pathways of various plant hormones have been identified, leading to the elucidation of partial or entire signaling cascades. These findings have provided the tools to begin addressing the mechanisms underlying the cross talk among different hormone signal transduction pathways. Such cross talk involves diverse mechanisms, which act at both the hormone response and biosynthesis levels, creating a delicate response network. In this review, we describe how gibberellin (GA) interacts with other plant hormones, concentrating on its interactions with abscisic acid (ABA), auxin, ethylene, and cytokinin. Although evidence for interactions of GA with brassinosteroids (Bouquin et al., 2001) and jasmonate (Traw and Bergelson, 2003) also exists, we focus on studies addressing the mechanisms governing the cross talk.