Identification of tomato Lhc promoter regions necessary for circadian expression.

Expression of the light-harvesting complex protein genes (Lhc) is under the control of a circadian clock. To dissect the molecular regulatory components of the circadian clock a promoter deletion analysis of four tomato Lhc genes was performed in transgenic tobacco plants. The important 5'-upstream promoter regions are present at different positions relative to the transcription start site of Lhc b1*1, b1*2, Lhc a3 and Lhc a4. A short sequence of 47 nucleotides is necessary for conferring circadian Lhc mRNA oscillations. Sequence alignment of the specified promoter regions revealed a novel motif 'CAANNNNATC'. This motif is conserved in 5'-upstream regions of clock controlled Lhc genes and overlaps with a sequence relevant in phytochrome mediated gene expression.