Identification and functional analysis of 23 novel box C/D snoRNAs from Oryza sativa

摘要

In a cDNA library generated from rice small nuclear RNAs, 30 box C/D small nuclcolar RNAs (snoRNAs) were identified through preliminary screen. Except 7 known snoRNAs such as U14, all snoRNAs were identified in rice for the first time experimentally. Among the 23 novel snoRNAs, 11 snoRNAs appear rice-specific, 6 snoRNAs are unique to plants, the remaining 6 snoRNAs have their counterparts in both Arabidopsis and yeast or mammals according to the conserved antisense sequences that guide 2'-O-ribosemethylation of rRNA. 17 of the 23 novel snoRNAs were predicted to guide 24 2'-O-ribose methylations at the specific sites of rice 5.8S, 18S, 25S rRNAs, among which 19 methylated sites were determined by primer extension at low dNTP concentrations. The remaining 6 snoRNAs devoid of rRNA antisense elements may represent novel snoRNA species in rice. The results show that constructing a cDNA library from small nuclear RNAs is an effective experimental approach for novel snoRNA identification. The novel snoRNAs are important in elucidating the genomic organization and expression of plant snoRNA genes and the mechanism through which 2'-O-ribose methylations took place in rRNAs.