Dawning of a new era: photomorphogenesis as an integrated molecular network.

Plant growth is shaped by the dynamic integration of environmental, developmental, and metabolic cues. Information from many of these input pathways feeds into the highly connected network of small molecule phytohormones. Signal transduction components for most plant hormones are known and mapping of hormone interactions within the network is well underway. Recent investigations of seedling photomorphogenesis, using well-established physiological and genetic tools in combination with sophisticated application of newer genomic technologies, provide a systems-level view of early seedling development. Factors, such as light, the circadian clock, and organ-specific developmental programs, profoundly influence the hormone network. The integrative approaches described here clarify the mechanisms of signal integration while revealing the flexibility of such relationships.