Organization and transcription of the gene family encoding chlorophyll a/b-binding proteins in Nicotiana sylvestris.

Nine Lhcb1 genes encoding the light-harvesting chlorophyll a/b-binding proteins of photosystem II were isolated and characterized from Nicotiana sylvestris. Their nucleotide sequences are highly similar. Lhcb1 transcripts are accumulated in leaves and stems but not in roots and non-green cultured cells. RNase protection assay revealed that no transcripts were detected from the gene, Lhcb1*2, in Nicotiana tabacum. This finding raises the possibility that the amphidiploid tobacco cultivar (N. tabacum) lost one gene from the female progenitor (N. sylvestris) during evolution. Transcriptional initiation sites were mapped and found to be mostly cytidine residues, which is unique to the N. sylvestris Lhcb1 genes. Four of the nine genes have single start sites and the remaining genes possess multiple initiation sites. The TATA-like sequences of nine Lhcb1 genes can be classified into two groups; one that possesses a TTTATA sequence and the other that has a sequence diverged from it. The genes with single initiation sites belong to the first group. A consensus motif for the initiation region is CTC*A (C* for initiation site), which differs from those of other plant genes or mammalian genes.