Progressive maturation of the root apical meristem inArabidopsis thalianalateral roots

Abstract

Meristems are stem cells niches that support the formation of all plant organs and are either set during embryogenesis and maintained throughout the plant life or specified de novo, post-embryonically. The embryo-derived root apical meristem is organized around a group of infrequently dividing cells, the quiescent centre, that maintains the stem cells, organizes growth along two axes and owing to its resistance to 3ic stress can replace damaged stem cells. In most cases, lateral roots post-embryonically branch off the primary and establish a new root meristem which organization is identical to the primary root one. The cellular and molecular processes underpinning the emergence of new stem cell niches are not well known. Here, we characterize the de novo establishment of the root apical meristem in lateral roots. While the position of the new stem cell niche is set early during morphogenesis, its cellular layout, unique gene expression profile and mitotic quiescence are only acquired after emergence concomitant to the establishment of two diverging growth axis. Our results show that the intertwined attributes of the mature root stem cell niche are progressively acquired during lateral root formation, and support a model in which the position of the stem cell niche emerges from the establishment of diverging growth axis.

CYP79B2 and CYP79B3 contribute to root branching through production of the auxin precursor indole-3-acetonitrile

“…A detailed report of cell divisions during lateral root formation showed that cell expansion is the main driver of lateral root emergence, while cell numbers only increase after emergence, proposing that the new lateral root meristem is only actively dividing after emergence (Malamy and Benfey, 1997). Furthermore, a recent report showed that mitotic quiescence of the quiescent center was only established after emergence, together with establishment of the cellular layout and unique gene expression profiles of the stem cell niche (Berthet et al, 2022). We found that the expression domain of CYP79B3 shifts from a region underlying the lateral root primordia to the meristem of the lateral root after lateral root emergence.…”

The Arabidopsis TETRATRICOPEPTIDE‐REPEAT THIOREDOXIN‐LIKE (TTL) family members are involved in root system formation via their interaction with cytoskeleton and cell wall remodeling

“…Before the emergence and formation of a LR, the LRP in Arabidopsis must cross three cell layers: the endodermis, the cortex and the epidermis (Stoeckle et al., 2018). When a LRP forms four cell layers (stage IV), stem cells are defined within the developing apical meristem and the LRP breaks through the endodermis at approximately the same time (Banda et al., 2019; Berthet et al., 2022). This period of pre‐emergent LRP development is accompanied by TTL3 expression.…”

Lateral root branching: evolutionary innovations and mechanistic divergence in land plants

“…In some plants, QC is specified during LRP outgrowth but in other species, it happens after LR emergence (Torres‐Martínez et al ., 2019). Although the QC is specified at a very early stage of LRP in Arabidopsis , the SCN maturation is a progressive process during LR development (Berthet et al ., 2022). In Arabidopsis , WOX5 is a specific marker of QC and non‐cell‐autonomously regulates the SCN (Box 2; Tian et al ., 2014).…”