Santos and Thornburg (1992) isolated a Nicotiana
tabacum UMPS cDNA with an open reading frame of 461
amino acids. Southern blot analysis indicates that there is
only one UMPS sequence in the N. plumbaginifolia
genome and two in that of N. tabacum. More recently rice
UMPS cDNAs have been recovered from the collection of
MAFF (Ministry of Agriculture, Forestry and Fisheries) DNA
database (Japanese Rice Genome Project) based on their
sequence homology with the N. tabacum cDNA. Two different
rice UMPS cDNAs, Os-umps1a (AF210322) and Osump2
(AF210325) were characterized. While Os-umps1a
appears to encode both enzyme activities, the Os-ump2
gene product is predicted to have only ODC activity due to
an internal deletion within the OPRT region of the enzyme