XVI International Botanical Congess

The pra2 gene encodes a pea small GTPase, and its expression is down-regulated by phytochrome. We determined a pra2 cis-regulatory region involved in phytochrome down-regulation. Both 5�f- and internal deletion analyses revealed that the 93 bp sequence between -734 and -642 from the transcriptional start site was important for phytochrome down-regulation. This 93 bp region could confer light down-regulation when fused to the CaMV 35S promoter. Furthermore, linker-scanning analysis showed that a 12 bp element mediated phytochrome down-regulation. Gel retardation analysis showed the presence of a nuclear factor that was specifically bound to the 12 bp sequence in vitro. We propose a model of phytochrome down-regulation of the pra2 gene.