MicroRNAs (miRNAs) and Plant Development

Development in plants is a continuous process during which new tissues and organs are formed all along its life cycle. Development involves the coordination of both time and space of complex cellular processes such as proliferation, expansion and differentiation following endogenous programmes and in response to environmental signals. Since their discovery in 2002, plant microRNAs (miRNAs), a class of small single-stranded regulatory ribonucleic acids (RNAs) have emerged as important nodes in regulatory networks controlling plant development. For instance, miRNAs play important roles for cell fate determination during the patterning of organs and contribute to the regulation of their growth. In addition, miRNAs integrate different signals to regulate the life cycle of plants. Finally, miRNAs appear as molecular links between environmental signals and plant development and may constitute levers to modify plant development in crops.

Key Concepts

  • miRNAs are essential for plant development as mutants affecting miRNA biogenesis or function are embryo lethal or show severe pleiotropic defects.
  • miRNA precursors are mostly produced from independent genetic units and are processed into mature miRNAs via a complex core machinery.
  • miRNAs can have different effects on the expression of their target genes, controlling their spatial pattern, their level of expression or the timing of their expression.
  • miRNAs are regulating many different developmental processes, including pattern formation, morphogenesis and differentiation at all stages of a plant's life.
  • Most of the miRNAs regulating plant development are evolutionary conserved and target evolutionary conserved transcription factors.
  • miRNAs can act non-cell-autonomously, generating a mobile signal that contributes to pattern formation through the regulation of the expression pattern of their targets.
  • miRNAs are integrated into complex regulatory networks and their expression is regulated by both endogenous and exogenous signals.

In: eLS. John Wiley & Sons, Ltd: Chichester.

DOI: 10.1002/9780470015902.a0020106.pub2

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Leaf development: what it needs to be complex.

Formation of dissected compound leaves involves the transient maintenance of an indeterminate environment and the generation of new growth axes that will generate leaflets. Recent work has revealed additional multi-layered mechanisms controlling the activities of the KNOXI homeodomains factors that play a prominent role in the control of indeterminacy associated with compound leaf development. Patterning and individualisation of the leaflets has been shown to involve gradients of the phytohormone auxin and the contribution of the NAM/CUC3 boundary genes. Identification of these novel actors governing compound leaf development opens the opportunity for further comparative studies aimed at understanding the molecular basis of leaf shape evolution.

Curr Opin Plant Biol, 2010, 13(1):75-82.

DOI: 10.1016/j.pbi.2009.09.017

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