Identification And Functional Analysis Of MicroRANs In An Alpine "Glasshouse Plant" Rheum Nobile(Polygonaceae)

MicroRNAs (miRNAs) are a new class of small,endogenous non-coding RNAs and play important roles in the post-transcriptional level of gene expression through sequence complementarity to target mRNAs. In plants, a majority of miRNAs perfectly or near-perfectly bind to their targeted mRNAs, thus, mRNA cleavage is regarded as the major mechanism of miRNA-mediated gene regulation. MiRNAs play critical functions in almost all biological and metabolic processes in plants, including plant development and response to different environmental biotic and abiotic stresses. Although a large number of miRNAs have been identified from various plants, so far there have bene extensive studies on discovering miRNAs and analyzing their functions in model species and crops, information regarding miRNAs from other species in stress environments such as alpine plants remains largely unknown.In the study presented here, we first combined direct cloning, Solexa sequencing with computational techniques to identify 79 miRNAs families, 38 of these families are conserved and 41 are novel in "glasshouse plant" Rheum nobile (Polygonaceae). Rheum nobile (Polygonaceae)which is endemic to the alpine zones of the eastern Himalayas, has been chosen as a model species for investigating "glasshouse plant". The upper leaves of what are termed "glasshouse plant" have been transformed into yellow and translucent bracts to adapt to alpine environments. To better understand the functional and regulatory mechanism about adaption to alpine environments of miRNAs in Rheum nobile (Polygonaceae), we comparison of small RNA expression patterns of the up and down leaves and predicting the targets of them, showed that all putative miRNAs involved in photosynthesis had been up-regulated, while those related to stress response were downregulated in the up leaves. These differentially expressed miRNAs are highly congruent with phenotypic and anatomical differences between the up and down leaves, indicating that they are regulated at the miRNA level for adaption in alpine conditions.