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Cloning and Characterization of Micrornas from Sorghum

Zhang, Li
In plants, gene regulation guided by the microRNAs (miRNAs) plays a key role in normal growth and development, nutrient homeostasis and stress tolerance. MiRNAs post-transcriptionally regulate gene expression either by causing degradation or attenuating the expression of RNA targets. Thus, identification of miRNAs is as important as protein-coding genes. Sweet sorghum, a drought tolerant crop, is largely grown for grain production in northeast Africa and for fodder production in southern plains of the United States. Presently, sorghum has emerged as one of the model plants for biofuel production. To identify miRNAs expressed in Sorghum, we generated a small RNA library. Sequence analysis revealed the expression of 28 conserved miRNA families in Sorghum. Additionally, 14 novel miRNAs were found of which seven are conserved at least in one another monocot. Expression analysis indicated the diffrential expression of several conserved miRNAs in different tissues. Furthermore, small RNA blot analysis indicated that miRNAs such as miR395 and miR399 are induced under sulfate-, and phosphate-deprived conditions, respectively. We also predicted more than 100 potential targets for miRNAs and some of them were validated using modified 5'-rapid amplification of cDNA ends (RACE) assay. These findings suggest that a large number of conserved and novel miRNAs are encoded in the Sorghum genome.