Light-inducible and tissue-specific pea lhcp gene expression involves an upstream element combining enhancer- and silencer-like properties

Studies in viral and mammalian cell systems have identified regulatory elements, collectively termed enhancers, which are cis-acting elements effective in either orientation and at both 5′ and 3′ ends of a gene, and which increase transcription when linked to either their own or a heterologous promoter gene system^1-5. Certain upstream elements in yeast have also been shown to exert a negative effect on the rate of transcription of cell-cycle-specific genes and these have been called silencers⁶. Two of the best characterized plant gene families are those of the small subunit of the ribulose 1,5-bisphosphate carboxylase (rbcS) genes⁷ and the lightharvesting chlorophyll a/b-bind ing protein (lhcp) genes⁸. The first enhancer element in plants has recently been described showing that an upstream element of an rbcS gene could, in both orientations, confer light-inducible expression on a heterologous promoter/gene system⁹. We report here that a 247-base pair (bp) element from an lhcp gene acts not only as a light-inducible enhancer but also as a tissue-specific 'silencer'.