Alternatively, loss of Dicer may enhance other small RNA pathway by conceding effecter molecules that are necessary for both small RNA pathways.
However, it is clear from recent investigations that small RNA pathways are not down regulated, but transcript levels of various small RNA pathway genes show dynamic and complex changes during male gametophyte development [ 17].
Close to 19.5% (2537) of identified small RNAs correspond to protein-coding genes suggesting the regulation of the corresponding transcripts by silencing RNA pathways (see below).
This overlap between dpld as a modifier of polyQ protein toxicity and the CAG-RNA-based toxicity, coupled with the implication of P-granule involvement, supports the idea of RNA pathways going awry in both situations.
With regard to shRNAs, a report showed fatality in mice due to oversaturation of cellular microRNA/short hairpin RNA pathways.
In this paper, we review the current understanding of plant small RNA pathways, including the biogenesis and function of miRNAs, siRNAs, trans-acting siRNAs, and heterochromatic siRNAs.
An important number of miRNAs that are regulated by M. oryzae elicitors are known to be involved in small RNA pathways, including miRNA and heterochromatic pathways.
We also examine the evolutionary relationship among plant species of both their miRNAs and the key enzymatic components of the small RNA pathways.
The translation of these discoveries to rice and other species, combined with both forward and reverse genetics approaches used directly in those species, is facilitating the elucidation of plant small RNA pathways and activities.
Finally we provide an overview of similar molecular machineries across species where related small RNA pathways appear to drive the epigenetic reprogramming in germ cells and/or during early development in metazoans.
The diversification of small RNA pathways has been demonstrated and the miRNA pathway is known to be a conserved mechanism of gene regulation in eukaryotes [23].
