ABSTRACT
MicroRNAs are endogenous, noncoding, regulatory small RNA molecules in the size range of 21-24 nucleotides that regulate gene expression. miRNAs are processed from single stranded precursors containing stem-loop 242structures, by the endonuclease activity of RNAse III; DICER-LIKE1, later on generating a double stranded miRNA. One of the strands of mature double stranded miRNA thus formed, designated as guide strand is preferentially incorporated into an ARGONAUTE protein containing effector complex; RNA induced Silencing Complex to repress the expression of target RNA containing their complementary sequence in plants. miRNAs, regulate gene expression either by target mRNA degradation or translational repression. But plants have been reported to employ mostly mRNA degradation mechanism for silencing expression of genes. The biogenesis, stability and activities of miRNAs are tightly regulated to ensure their normal functions in various plant developmental processes, metabolism as well as plant’s responses to abiotic and biotic stresses. The focus of the present review will be on advances in molecular machinery and mechanisms involved in regulation of miRNA biogenesis and regulation of their role in controlling gene expression in plants. The underlying process of regulating miRNA levels through their turnover involving their stability and degradation are also briefly discussed.
