The pea light-independent photomorphogenesis1 mutant results from partial duplication of COP1 generating an internal promoter and producing two distinct transcripts

The pea lip1 (light-independent photomorphogenesis1) mutant shows many of t he characteristics of light-grown development when grown in continuous dark ness. To investigate the identity of LIP1, cDNAs encoding the pea homolog o f COP1, a repressor of photomorphogenesis identified in Arabidopsis, were i solated from wild-type and lip1 pea seedlings. lip1 seedlings contained a w ild-type COP1 transcript as well as a larger COP1' transcript that containe d an internal in-frame duplication of 894 bp. The COP1' transcript segregat ed with the lip1 phenotype in F-2 seedlings and could be translated in vitr o to produce a protein of similar to 100 kD. The COP1 gene in lip1 peas con tained a 7.5-kb duplication, consisting of exons 1 to 7 of the wild-type se quence, located 2.5 kb upstream of a region of genomic DNA identical to the wild-type COP1 DNA sequence. Transcription and splicing of the mutant COP1 gene was predicted to produce the COP-1' transcript, whereas transcription from an internal promoter in the 2.5-kb region of DNA located between the duplicated regions of COP1 would produce the wild-type COP1 transcript. The presence of small quantities of wild-type COP1 transcripts may reduce the severity of the phenotype produced by the mutated COP1' protein. The genomi c DNA sequences of the COP1 gene from wild-type and lip1 peas and the cDNA sequences of COP1 and COP1' transcripts have been submitted to the EMBL dat abase under the EMBL accession numbers AJ276591, AJ276592, AJ289773, and AJ 289774, respectively.