Characterization and regulation of the expression of the Solanum tuberosum Lhcb1 genes

A potato (Solanum tuberosum) genomic library was used to isolate five full-length genes and part of a sixth one, encoding the apoproteins of a light-harvesting complex (LHC). The nucleotide sequences of the five isolated genes showed that they encoded very similar proteins (99.75% to 97.50% identities). The deduced amino acid sequences were homologous to the PSII type I CAB proteins encoded by the Lhcb1 genes. The 5'-flanking regions of the five potato genes shared conserved sequences already detected in other light-responsive genes (62 bp fragment located between the CAAT and TATA boxes containing three GATA motifs). The expression of Lhcb1 genes in potato leaves, stems and roots was analyzed by the primer extension method. At least nine different transcripts can be recognized in leaves. A unique transcript could be detected in stems and not in roots. The regulatory function of the 5'-flanking region of the potato Lhcb1*2 was analyzed in transgenic tobacco plants. The construct used contained the gusA gene which was under the control of the potato Lhcb1*2 promoter. Analysis of transgenic plants revealed that the 5'-flanking region (-1300 to +10, relative to the transcription start site) of the Lhcb1*2 gene was sufficient to confer a phytochrome response as well as organ-specific expression.