The ‘how’ and ‘where’ of plant micro RNA s

Abstract

Summary: Micro RNA s (mi RNA s) are small non‐coding RNA s, of typically 20–24 nt, that regulate gene expression post‐transcriptionally through sequence complementarity. Since the identification of the first mi RNA, lin‐4, in the nematode Caenorhabditis elegans in 1993, thousands of mi RNA s have been discovered in animals and plants, and their regulatory roles in numerous biological processes have been uncovered. In plants, research efforts have established the major molecular framework of mi RNA biogenesis and modes of action, and are beginning to elucidate the mechanisms of mi RNA degradation. Studies have implicated restricted and surprising subcellular locations in which mi RNA biogenesis or activity takes place. In this article, we summarize the current knowledge on how plant mi RNA s are made and degraded, and how they repress target gene expression. We discuss not only the players involved in these processes, but also the subcellular sites in which these processes are known or implicated to take place. We hope to raise awareness that the cell biology of mi RNA s holds the key to a full understanding of these enigmatic molecules. Contents Summary 1002 I. MicroRNA biogenesis in plants 1002 II. Modes of action of miRNAs 1007 III. Turnover of miRNAs 1010 IV. Concluding remarks 1013 Acknowledgements 1013 References 1013