CHARACTERIZATION OF A RICE SUCROSE-PHOSPHATE SYNTHASE-ENCODING GENE

A rice genomic clone (sps1) coding for sucrose phosphate synthase (SPS ) was isolated and sequenced. Rice sps1 contains 13 exons and 12 intro ns, an unusually long 366-bp leader region with a highly organized pri mary structure and a promoter region with no obvious homology with euk aryotic promoter consensus sequences. Southern blot analysis showed th at SPS is encoded by a single-copy gene in the rice genome. Comparison of the rice, maize, potato and spinach SPS deduced amino acid (aa) se quences showed that these enzymes have a well conserved region compris ing their first 700 aa, and a variable C-terminal region. Analysis of rice sps1 expression showed that mRNA levels change during leaf develo pment. SPS activity and mRNA were undetectable in roots.