T-DNA tagging and characterization of a cryptic root-specific promoter in Arabidopsis. 
From a T-DNA tagged Arabidopsis population, a line, M-57 showing GUS (beta-glucuronidase) expression in the vascular regions of young roots was identified.  Southern analysis revealed presence of a single T-DNA insert.  Using inverse PCR, the plant sequence flanking the T-DNA insertion was cloned.  The insertion was identified to be in the intergenic area between loci At4G13940 and At4G13930, coding for SAHH (S-Adenosyl-l-Homocysteine Hydrolase) and SHMT (Serine Hydroxy Methyl Transferase) genes, respectively.  A 452-bp fragment immediately upstream of the T-DNA insertion when cloned and mobilized as a GUS fusion was capable of driving a similar root-specific expression of reporter gene in transgenic Arabidopsis plants and their progenies.  This cryptic promoter element does not show the presence of any known root-specific promoter element.