MicroRNAs as regulators of adventitious root development

MicroRNAs (miRNAs) are post-transcriptional regulators of growth and development in both plants and animals. In plants, the root system plays the essential role of anchoring plants to the soil and allowing the uptake of nutrients and water. Adventitious rooting is an essential step in the vegetative propagation of economically important horticultural and woody species. It facilitates clonal propagation and rapid fixation of superior genotypes prior to their introduction into production or breeding programs. Severe economic losses occur due to limitations in understanding the molecular pathways involved in establishing and maintaining adventitious root growth. In this review, we describe recent advances in the identification of miRNAs involved in adventitious root growth, focusing on the model plant Arabidopsis and its relevance to hard-to-root woody species. We summarise the current knowledge on the interactions between light, auxin, Auxin Response Factors (ARFs) and microRNAs that combine to influence, or potentially influence adventitious root production. A greater understanding of these processes will be crucial for the design and manipulation of plant biochemistry to obtain commercially viable rootstocks and clones of many important woody species.