Sequencing and characterization of the macronuclear rDNA minichromosome of the protozoan Tetrahymena pyriformis

Xiaojie Han; Guanxiong Yan; Yang Ma; Wei Miao; Guangying Wang

doi:10.1016/j.ijbiomac.2020.01.063

Sequencing and characterization of the macronuclear rDNA minichromosome of the protozoan Tetrahymena pyriformis

Int J Biol Macromol. 2020 Mar 15:147:576-581. doi: 10.1016/j.ijbiomac.2020.01.063. Epub 2020 Jan 10.

Authors

Xiaojie Han¹, Guanxiong Yan², Yang Ma², Wei Miao³, Guangying Wang⁴

Affiliations

¹ College of Fisheries and Life Science, Dalian Ocean University, Dalian 116023, China; Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
³ College of Fisheries and Life Science, Dalian Ocean University, Dalian 116023, China; Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China; State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; CAS Center for Excellence in Animal Evolution and Genetics, Kunming 650223, China.
⁴ Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China. Electronic address: wangguangying@ihb.ac.cn.

PMID: 31931068
DOI: 10.1016/j.ijbiomac.2020.01.063

Abstract

Tetrahymena ribosomal DNA (rDNA) is an ideal system for studying eukaryotic DNA replication and gene transcription. In this study, we developed a new method to isolate rDNA from Tetrahymena cells and used it to sequence and annotate the complete 19,670 bp macronuclear rDNA minichromosome of Tetrahymena pyriformis, a species that lacks the germ-line micronucleus and is unable to undergo sexual reproduction. The key features of T. pyriformis and Tetrahymena thermophila rDNA sequences were then compared. Our results showed (i) the short inverted repeats (M repeats) essential for formation of rDNA minichromosome palindromic structure during sexual reproduction in Tetrahymena are highly conserved in T. pyriformis; (ii) in contrast to T. thermophila, which has two tandem domains that coordinately regulate rDNA replication, T. pyriformis has only a single domain; (iii) the 35S pre-rRNA precursor has 80.25% similarity between the two species; and (iv) the G + C content is higher in the transcribed region than the non-transcribed region in both species, but the GC-skew is more stable in T. pyriformis. The new isolation method and annotated information for the T. pyriformis rDNA minichromosome will provide a useful resource for studying DNA replication and chromosome copy number control in Tetrahymena.

Keywords: Palindrome; Tetrahymena pyriformis; rDNA minichromosome.

MeSH terms

Animals
Chromosomes / genetics*
DNA Replication / genetics*
DNA, Ribosomal / genetics*
Sequence Analysis, DNA
Tetrahymena pyriformis / genetics*
Tetrahymena thermophila / genetics

Substances

DNA, Ribosomal