No miRNA were found in Plasmodium and the ones identified in erythrocytes could not be correlated with infection

Of 132 small RNA sequences, no Plasmodium-specific miRNAs have been found. However, a human miRNA, miR-451, was highly expressed, comprising approximately one third of the total identified miRNAs. Further analysis of miR-451 expression and malaria infection showed no association between the accumulation of miR-451 in Plasmodium falciparum-iRBCs, the life cycle stage of P. falciparum in the erythrocyte, or of P. berghei in mice. Moreover, treatment with an antisense oligonucleotide to miR-451 had no significant effect on the growth of the erythrocytic-stage P. falciparum.Short RNAs from a mixed-stage of P. falciparum-iRBC were separated in a denaturing polyacrylamide gel and cloned into T vectors to create a cDNA library. Individual clones were then sequenced and further analysed by bioinformatics prediction to discover probable miRNAs in P. falciparum-iRBC. The association between miR-451 expression and the parasite were analysed by Northern blotting and antisense oligonucleotide (ASO) of miR-451.These results contribute to eliminate the probability of miRNAs in P. falciparum. The absence of miRNA in P. falciparum could be correlated with absence of argonaute/dicer genes. In addition, the miR-451 accumulation in Plasmodium-infected RBCs is independent of parasite infection. Its accumulation might be only the residual of erythroid differentiation or a component to maintain the normal function of mature RBCs.MicroRNAs (miRNAs), a newly discovered class of endogenous ~21 nucleotide regulatory non-coding small RNAs, post-transcriptionally regulated gene expression in eukaryotes by targeted RNA degradation and translational arrest [1]. Similarly to short interfering RNAs (siRNAs), miRNAs are produced in the cytoplasm from a precursor, which contains an imperfectly matched inverted repeat forming a partial double-stranded region, by the ribonuclease, dicer. One strand of the resulting miRNA duplex intermediate is then recruited by the argonaute nuclease, an enzyme involve