Phytochrome Regulated Expression of Cab Genes in Higher Plants

In higher plants the chlorophyll a/b binding protein is encoded by small multigene families (I). We have isolated and characterized the Cab-I gene from wheat (2). We have shown that the Cab-I gene is expressed in a tissue-specific, light-inducible manner. The regulated expression of the Cab-I gene is controlled by phytochrome and manifested at the level of transcription (3). Recently we have demonstrated that the expression of the Cab-I gene is also controlled by an endogenous circadian rythm (4). Both the circadian rythm and the phytochrome mediated light response of the Cab-I gene can be recapitulated in transgenic tobacco plants. In vitro DNA sequence manipulation coupled with expression in transgenic plants revealed cis-acting elements for the regulated expression of this gene. One of these elements, a ca. 260 bp upstream enhancer-like sequence of the Cab-l gene confers phytochrome controlled, tissue­ specific expression to constitutive promoters (5). Detailed analysis of this element has revealed a complex array of multiple regulatory sequences for the for the expression of the Cab-I gene.