Loss of a Fragile Chromosome Region leads to the Screwy Phenotype in Paramecium tetraurelia

Genes

Irina Nekrasova¹  Alexey Potekhin¹  Vera Nikitashina¹  Eric Meyer²  DeepankarP. Singh²  Simran Bhullar²  Olivier Arnaiz³ 

[1] Department of Microbiology, Faculty of Biology, Saint Petersburg State University, Universitetskaya nab. 7/9, 199034 Saint Petersburg, Russia;IBENS, Département de Biologie, Ecole Normale Supérieure, CNRS, Inserm, PSL Research University, F-75005 Paris, France;Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette CEDEX, France;

关键词: Paramecium;    micronuclear deletion;    chromosome fragile sites;    cortical inheritance;    trichocysts;    epimutation;    maternal inheritance;   

DOI  :  10.3390/genes10070513

来源: DOAJ

【 摘 要 】

A conspicuous cell-shape phenotype known as “screwy” was reported to result from mutations at two or three uncharacterized loci in the ciliate Paramecium tetraurelia. Here, we describe a new screwy mutation, Spinning Top, which appeared spontaneously in the cross of an unrelated mutant with reference strain 51. The macronuclear (MAC) genome of the Spinning Top mutant is shown to lack a ~28.5-kb segment containing 18 genes at the end of one chromosome, which appears to result from a collinear deletion in the micronuclear (MIC) genome. We tested several candidate genes from the deleted locus by dsRNA-induced silencing in wild-type cells, and identified a single gene responsible for the phenotype. This gene, named Spade, encodes a 566-aa glutamine-rich protein with a C₂HC zinc finger. Its silencing leads to a fast phenotype switch during vegetative growth, but cells recover a wild-type phenotype only 5−6 divisions after silencing is stopped. We analyzed 5 independently-obtained mutant alleles of the Sc1 locus, and concluded that all of them also lack the Spade gene and a number of neighboring genes in the MAC and MIC genomes. Mapping of the MAC deletion breakpoints revealed two different positions among the 5 alleles, both of which differ from the Spinning Top breakpoint. These results suggest that this MIC chromosome region is intrinsically unstable in strain 51.

【 授权许可】

Unknown