AN ALFALFA RUBISCO SMALL-SUBUNIT HOMOLOG SHARES CIS-ACTING ELEMENTS WITH THE REGULATORY SEQUENCES OF THE RBCS-3A GENE FROM PEA

A genomic clone of RbcS was isolated from an alfalfa (Medicago sativa L. cv. Apica) genomic library and characterized. Although this clone h as structural features similar to a functional gene, the second exon i s interrupted by a stop codon and thus is not fully translatable in th e plant. Sequence analysis of the 5' and 3' noncoding regions of RbcSK -1A showed a high sequence homology to the flanking sequences of the R bcS-3A gene from pea. The regions of homology contain many important c is-regulatory elements shown to be essential for regulation of the Rbc S-3A gene in pea. The promoter of this alfalfa rubisco clone was used in a translational fusion to test its ability to control the expressio n of the GUS reporter gene in an homologous nuclear background. High l evels of GUS enzyme activity were recorded. These strong levels are co mparable to some exceptionally high levels produced in other studies f ollowing the use of photosynthesis gene promoters in fusions with the GUS reporter gene. (C) 1997 Elsevier Science B.V.