Control of quiescent centre formation in adventitious roots

Adventitious roots (ARs) are part of the root system in numerous plants, and are required for successful micropropagation. Della Rovere et al. study the quiescent centre (QC) in ARs of Arabidopsis thaliana and find that accumulation of auxin and the expression of the QC marker WOX5 characterize the early derivatives of the AR founder cells both in planta and in explants. An auxin maximum is determined to occur at the AR tip, to which WOX5 expression is restricted, establishing the positioning of the QC. Cytokinin causes a restriction of LAX3 and PIN1 expression domains, and concomitantly the auxin biosynthesis YUCCA6 gene is expressed in the apex. They conclude that establishment of the QC requires the co-ordinated action of auxin and cytokinin.