ACTIVITY OF THE PROMOTER OF THE LHCA3.ST.1 GENE, ENCODING THE POTATO APOPROTEIN-2 OF THE LIGHT-HARVESTING COMPLEX OF PHOTOSYSTEM-I, IN TRANSGENIC POTATO AND TOBACCO PLANTS

We have isolated cDNA and genomic clones for the potato (Solanum tuber osum) apoprotein 2 of the light harvesting complex of Photosystem 1, d esignated Lhca3.St.l. The protein shows all characteristics of the fam ily of chlorophyll a/b-binding proteins. Potato Lhca3.1 gene expressio n occurs predominantly in leaves,and is transcriptionally regulated by light. One gene copy is present per haploid genome. The sequence of t he 5' upstream region was determined. Most boxes identified in the pro moter sequences of genes whose expression is light-regulated recur in the Lhca3.St.1 sequence. Functional analyses of the Lhca3. St.1 promot er and two deletion derivatives in transgenic potato transformed with a promoter-GUS fusion show high promoter activity in leaves and other green parts of the plant, which depends on light. Activity is absent i n roots and potato tubers. The 500 bp promoter fragment is as active a s the full 2.0 kb sequence, showing that all regulatory elements are p resent on the smallest deletion derivative. In transgenic tobacco (Nic otiana tabacum) plants carrying the largest promoter derivative a simi lar distribution of activity is found. Promoter activity is not restri cted to the phloem, but also prominent in the xylem of the young stem, Which contrasts with promoters of other photosynthesis-associated gen es.