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MicroRNAs (miRNAs) are major post-transcriptional regulators of gene expression. They base pair with the complementary target mRNA at the 3 0 UTR and modulate cellular processes by repressing the mRNA translation or degrading the mRNA. There are well-documented mechanisms of biogenesis of miRNA; however, a sizeable number of miRNAs are also produced by noncanonical pathways. Mirtrons represent a predominant class of non-canonical miRNAs. Mirtrons originate from intronic regions and are produced in a splicing-dependent and Drosha-independent manner. Mirtrons constitute about 15% of all miRNAs produced in a human body and have caught attention of researchers worldwide due to their unconventional origin, sequence characteristics, evolutionary dynamics, ability to regulate variety of cellular processes and their immense potential in disease therapeutics. In this comprehensive review we collate the research done in the past decade including biogenesis, sequence characteristics, regulation, and emerging therapeutic roles of mirtrons.

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Seabuckthorn (Hippophae rhamnoides L.), an upcoming superfood plant, has attracted researchers' attention worldwide for its medicinal, nutritional, and socio-economic value, along with its characteristic features to sustain extreme climatic conditions. We have studied microsatellite marker-based genetic and morphometric diversity in 93 collections of H. rhamnoides from different geographic sites representing two regions, namely Leh and Lahaul of the Indian Himalayas. Microsatellite markers were isolated using two different approaches, including screening of microsatellite-enriched genomic library, and in silico screening of in-house developed seabuckthorn EST database and whole transcriptome assembly. In Leh and Lahaul collections, 32 and 30 microsatellite markers were found polymorphic, respectively. All the markers developed for H. rhamnoides showed cross-species transferability to H. salicifolia and H. tibetana. Two to six alleles were recorded in the two sets of collections with an average of 3.71 and 3.53 alleles per locus in Leh and Lahaul collections, respectively. Mean polymorphic information content (PIC) values for microsatellite markers were 0.39 and 0.41 for Leh and Lahaul collections, respectively. The average expected heterozygosity was less than the observed heterozygosity. Wright's fixation index (F IS ) varied from (−)0.2045 to 1.0 and (−)0.1688 to 1.0 for Leh and Lahaul collections, respectively. Shannon's informative index (I) remained in the range of 0.6745 to 1.8621, and 0.6824 to 1.6308 for Leh and Lahaul collections, respectively. The UPGMA-based combined dendrogram showed clear demarcation between Leh and Lahaul collections, although a few ecotypes were regrouped with collections from the other region. No significant relationship was observed between the morphological distance matrix and molecular marker distance matrix. The findings of the present study may prove helpful in future breeding and conservation strategies aiming for seabuckthorn improvement. KeywordsGenetic diversity • Hippophae rhamnoides • Microsatellites • Molecular markers • Morphometry • Seabuckthorn Key Message • We report microsatellite marker-based genetic and morphometric diversity in 93 collections of seabuckthorn representing different geographic sites in the Indian Himalayas. • In Leh and Lahaul collections, 32 and 30 microsatellite markers were found polymorphic. • The UPGMA-based combined dendrogram showed clear demarcation between Leh and Lahaul collections. • Our findings are useful for seabuckthorn breeding and conservation programs.

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