ABSTRACT
With the rapid development of genomics and bioinformatics, recent studies have suggested that the number of protein-coding genes is similar in many model eukaryotes whose whole genome sequences have been obtained and analyzed in detail (Matera et al. 2007; Ponting et al. 2009). Genome-wide transcriptional analyses have identifi ed large numbers of non-coding RNAs (ncRNAs) in humans, animals and plants (Hirsch et al. 2006; Ravasi et al. 2006; The ENCODE Project Consortium 2007; Guttman et al. 2009; Amor et al. 2009; Jouannet et al. 2011). Based on their length, ncRNAs can be arbitrarily divided into small ncRNAs, intermediate-size ncRNAs and long ncRNAs (Amor et al. 2009; Jouannet et al. 2011; Liu et al. 2013). To date, the best characterized of all the ncRNAs has been small RNAs (sRNAs). Endogenous small RNAs are about 19-30 nucleotides (nt) RNA molecules that modulate
1State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China. Email: dyli@genetics.ac.cn 2Department of Genetics and Biochemistry, Clemson University, 110 Biosystems Research Complex, Clemson, SC 29634. *Corresponding author: hluo@clemson.edu
gene expression at the transcriptional and/or posttranscriptional levels and play key roles in many developmental and physiological processes in eukaryotic organisms (Zamore and Haley 2005; Bonnet et al. 2006; Zhang et al. 2006; Ramachandran and Chen 2008; Poethig 2009).
