Characterization of the signal recognition particle (SRP) RNA population of tomato (Lycopersicon esculentum)

Abstract

Molecular cloning of 30 cDNAs and subsequent characterization of the corresponding SRP RNA from four cultivars of tomato (Lycopersicon esculentum) revealed altogether 14 sequence variants, which could be ordered into six groups. The expression of five representatives from these groups was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) in different cultivars and different tissues. Although one cultivar-specific SRP RNA variant could be detected in the leaf SRP RNA population, identical SRP RNA populations seem to be present in the four different cultivars as well as in different tissues, such as leaves, flowers, fruits, stems and roots. Sequence comparison revealed that several variants might have evolved by recombination of two different SRP RNA sequences. On the basis of five SRP RNA variants, the current secondary structure model was refined and a new conserved structural element was detected. Comparative sequence analysis of domain II from all known SRP RNA homologues reveals a remarkable conservation of this element. As demonstrated previously, the corresponding area overlaps with a region that interact with the SRPp68/p72 heterodimer and/or with ribosomes. Based on structural and functional considerations, we propose that the domain IV structure together with the highly conserved area of domain II constitutes the essential core of the SRP RNA.

Molecular analysis of the gene family of the signal recognition particle (SRP) RNA of tomato

“…Our previous analysis of several SRP RNA sequence variants from tomato has indicated that at least ten different SRP RNA genes are present in the tomato genome [42]. This assumption could now be confirmed by Southern analysis (Fig.…”

“…In this work, Mtlhlbach and Sanger [34] demonstrated the resistance of 7S RNA transcription to c~-amanitin. Additional support was provided by our results from direct sequencing of the tomato SRP RNA [18] and recently of fulllength cDNAs [42]. All sequence variants possess three to five uridines at the very 3'-end which points to the pol Ill-specific transcription termination within DNA-stretches of thymidine residues [ 15].…”

“…Southern hybridization was carried out at 42 °C or more stringent at 65 °C according to the method of Amasino [ 1 ] using previously isolated tomato SRP cDNA variants [42] as probes. These probes were labeled with 32p in a randomprimed DNA-labelling reaction (Boehringer).…”

“…First informations on the sequence and a secondary structure model of plant SRP RNA came from our characterization of the 7S RNA from the dicot tomato [18] which was later complemented by our detailed characterization of the tomato SRP RNA population [42]. Additional dicot SRP RNA sequences were studied in Arabidopsis thaliana [22,29,46].…”

“…SRP RNA sequences from monocots were determined in maize [ 7 ] and wheat [ 31 ]. Nevertheless, despite the high sequence diversity of SRP RNAs found in the SRP RNA populations from different plant species and from individual plants, evolutionary well conserved RNA secondary structures could be detected [27,42].…”