Thymine-starvation up-regulates a region of theArabidopsis thaliana chromosome III containing both the UMP synthase gene and a proximal gene encoding a novel F-box protein

Abstract

We have cloned theArabidopsis thaliana undine 5′-monophosphate synthase (UMP synthase) locus and characterized transcript levels of this gene as well as the transcript encoding a novel F-box protein found upstream of UMP synthase,Skp1-interacting partner5 (SKIPS). The 31 end of theSKIP5 gene is 405 bp from the 5′ end of the UMP synthase gene. To determine whether these proximate genes are coordinately or independently regulated, we have used an RT-PCR method to quantitate the transcript levels of each gene relative to 18S ribosomal RNA. Previous work has demonstrated an up-regulation of the UMP synthase gene in tobacco callus in the presence of compounds such as 5-fluoroorotate and aminopterin that induce thymine starvation. Here, we present results showing that both the UMP synthase andSKIP5 genes are coordinately up-regulated in the presence of fluoroorotic acid.