More ribosomal spacer sequences from Xenopus laevis

Area of Science:

• Molecular Biology
• Genomics
• Evolutionary Biology

Background:

• Ribosomal DNA (rDNA) plays a crucial role in protein synthesis.
• Understanding rDNA structure and evolution provides insights into gene regulation and organismal divergence.
• The non-transcribed spacer (NTS) and external transcribed spacer (ETS) regions of rDNA are critical for rDNA repeat stability and transcription initiation.

Purpose of the Study:

• To present a comprehensive sequence analysis of the Xenopus laevis rDNA repeat, focusing on the NTS and ETS.
• To identify and characterize repetitive and non-repetitive sequence elements within the spacer regions.
• To compare sequence conservation between Xenopus laevis and Saccharomyces cerevisiae rDNA, particularly in the 18S gene and ETS.

Main Methods:

• DNA sequencing of the Xenopus laevis ribosomal DNA repeat.
• Bioinformatic analysis to identify repetitive and non-repetitive elements.
• Comparative sequence analysis between Xenopus laevis and Saccharomyces cerevisiae rDNA.

Main Results:

• The study presents compiled sequences covering nearly the entire NTS and ETS of Xenopus laevis rDNA.
• Repetitive and non-repetitive sequence elements within the spacer regions were identified and their evolutionary significance discussed.
• Approximately 80% sequence conservation was observed in the 18S gene between Xenopus laevis and Saccharomyces cerevisiae, while no significant conservation was found in the ETS.

Conclusions:

• The Xenopus laevis rDNA spacer regions contain distinct repetitive and non-repetitive elements with evolutionary implications.
• Significant divergence exists in the ETS between Xenopus laevis and Saccharomyces cerevisiae, despite conservation in the 18S gene.
• The sequence and structural features of the 3' terminus of the Xenopus laevis 40S ribosomal precursor RNA were analyzed.