Group-I introns with unusual sequences occur at three sites in nuclear 18S rRNA genes of Acanthamoeba lenticulata.
Seven of eleven isolates of Acanthamoeba lenticulata were found to have group-I introns located at one of three positions within the 18S rRNA gene. The introns are 636-721-bp long and are absent from mature rRNA. They lack open reading frames that could encode any known endonucleases. Sequences of introns from the same site in different isolates are 86.0-98.9% identical, while from different sites they are 24.2-29.8% identical. The most closely related introns from other organisms are in the 18S rRNA genes of several green algae where the 17.0-23.6% identity is mostly limited to a highly conserved core of base pairs including P, Q, R and S. Because the A. lenticulata introns only occur in one Acanthamoeba lineage, they were probably acquired after the divergence of this species.
Department of Molecular Genetics, The Ohio State University, 484 W 12th Avenue, Columbus, OH 43210-1292, USA.
J M
JM
Schroeder-Diedrich
P A
PA
Fuerst
T J
TJ
Byers
D000048:Acanthamoeba / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D016054:DNA, Protozoan / Q000737:chemistry*; D004275:DNA, Ribosomal / Q000737:chemistry; D019143:Evolution, Molecular; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012337:RNA, Ribosomal, 18S / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid
D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S