"At the root of quiescence - Function and regulation of the quiescent center in roots".

The quiescent center (QC) of roots consists of a rarely dividing pool of stem cells within the root apical meristem (RAM). The QC maintains the surrounding more frequently dividing initials, together building the stem cell niche (SCN) of the RAM. The initials, after several rounds of divisions and differentiation, give rise to nearly all tissues necessary for root function. Hence, QC establishment, maintenance and function are key to produce the whole plant root system and are therefore at the foundation of plant growth and productivity. Although the concept of the QC is known since the 1950s, much of its molecular regulations and their intricate interconnections, especially in more complex root systems like cereal RAMs remain elusive. In Arabidopsis, molecular factors like phytohormones, small signaling peptides and their receptors, as well as key transcription factors (TFs) play important roles in a complex and intertwined regulatory network. In cereals, homologs of these factors are present, however, QC maintenance in these larger RAMs might also require a more complex control of QC cell regulation by a combination of asymmetric and symmetric divisions. Here, we summarise the current knowledge on QC maintenance in Arabidopsis and compare it with that of agriculturally relevant cereal crops.