title: Evolution of the germline actin gene in hypotrichous ciliates: multiple nonscrambled IESs at extremely conserved locations in two urostylids.
abstract: In hypotrichous ciliates, macronuclear chromosomes are gene-sized, and micronuclear genes contain short, noncoding internal eliminated segments (IESs) as well as macronuclear-destined segments (MDSs). In the present study, we characterized the complete macronuclear gene and two to three types of micronuclear actin genes of two urostylid species, i.e. Pseudokeronopsis rubra and Uroleptopsis citrina. Our results show that (1) the gain/loss of IES happens frequently in the subclass Hypotrichia (formerly Stichotrichia), and high fragmentation of germline genes does not imply for gene scrambling; and (2) the micronuclear actin gene is scrambled in the order Sporadotrichida but nonscrambled in the orders Urostylida and Stichotrichida, indicating the independent evolution of MIC-actin gene patterns in different orders of hypotrichs; (3) locations of MDS-IES junctions of micronuclear actin gene in coding regions are conserved among closely related species.
authors.affiliation: Laboratory of Protozoology, School of Life Science, South China Normal University, Guangzhou, 510631, China.
authors.forename: Tianbing
authors.initials: T
authors.lastname: Chen
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: Yi
authors.forename: Jie
authors.initials: J
authors.lastname: Huang
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Lin
mesh_terms: D000199:Actins / Q000235:genetics*; D001483:Base Sequence; D002875:Chromosomes; D016054:DNA, Protozoan / Q000737:chemistry*; D019143:Evolution, Molecular; D017125:Genes, Protozoan; D016810:Hypotrichida / Q000235:genetics*
chemical_list: D000199:Actins; D016054:DNA, Protozoan
keywords: Actin; MDS; ciliates; macronuclear; micronuclear