Destabilization of chimeric rbcL 5`UTR:GUS transcripts by changing nucleotides in the second half of the UTR sequence

The Clamydomonas chloroplast rbcL gene encodes the large subunit of ribulose-bisphosphate carboxylase (RUBISCO). The 5`untranslated region (5`UTR) of the rbcL gene is crucial for its transcripts stability. Previous studies have shown that an RNA secondary structure (stem-loop), predicted to form at the beginning of the 5`UTR, plays an important role in RNA stabilization. In this report we examined the function of a smaller second RNA stem-loop, in vivo, that is predicted to form after the terminal stem-loop at the 5`end of transcripts of the Chlamydomonas reinhardtii chloroplast rbcL gene. Three nucleotides were altered at position +50 to +52 in the stem-loop sequence to study its role in RNA stability. The results show that these changes destabilize the transcripts in Chlamydomonas reinhardtii