Contrary operations of Box-I element of pea phenylalanine ammonia-lyase gene 1 promoter for organ-specific expression

Expression of genes (PSPAL) encoding phenylalanine ammonia-lyase from pea ( Pisum sativum L.) is regulated in response to various environmental stimuli and during plant development. We examined the cis-regulatory elements in P SPAL1 promoter for organ-specific expression by determining the sequences s pecifically associated with nuclear proteins on its promoter in each pea or gan. In vivo dimethyl sulfate (DMS) footprinting analysis showed putative p rotein bindings on AC-rich sequences including Box-I in particular in roots and stems in which PSPAL mRNA were highly accumulated. The potential role of the AC-rich element was investigated by fusing PSPAL1 promoter with Box- I deleted to the reporter gene P-glucuronidase (GUS) and transforming the c onstruct into tobacco plants (Nicotiana tabacum). GUS activity controlled u nder this Box-I deletion promoter was significantly reduced in roots and le aves, whereas drastically increased in stems as compared with the activity of wild-type PSPALI promoter. Histochemical GUS staining indicated the acti vity was elevated in vascular tissues of stem by deleting Box-I. These resu lts suggest that Box-I in PSPALI contributes to a positive regulation in ro ot and leaf, but might also function as a negative regulator in stem, espec ially in xylem tissue. (C) 2001 Editions scientifiques et medicales Elsevie r SAS.