Conservation of small RNA pathways in platypus.
Small RNA pathways play evolutionarily conserved roles in gene regulation and defense from parasitic nucleic acids. The character and expression patterns of small RNAs show conservation throughout animal lineages, but specific animal clades also show variations on these recurring themes, including species-specific small RNAs. The monotremes, with only platypus and four species of echidna as extant members, represent the basal branch of the mammalian lineage. Here, we examine the small RNA pathways of monotremes by deep sequencing of six platypus and echidna tissues. We find that highly conserved microRNA species display their signature tissue-specific expression patterns. In addition, we find a large rapidly evolving cluster of microRNAs on platypus chromosome X1, which is unique to monotremes. Platypus and echidna testes contain a robust Piwi-interacting (piRNA) system, which appears to be participating in ongoing transposon defense.
Murchison
Elizabeth P
EP
Watson School of Biological Sciences, Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
Kheradpour
Pouya
P
Sachidanandam
Ravi
R
Smith
Carly
C
Hodges
Emily
E
Xuan
Zhenyu
Z
Kellis
Manolis
M
Grützner
Frank
F
Stark
Alexander
A
Hannon
Gregory J
GJ
D000818:Animals; D001483:Base Sequence; D019143:Evolution, Molecular; D008297:Male; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010987:Platypus / Q000235:genetics*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014960:X Chromosome
D035683:MicroRNAs; D034741:RNA, Small Interfering