Béatrice Berthet

Long-lived species suppress cancer despite accumulating somatic mutations throughout life, but how this is achieved in renewing tissues remains unclear. Here, we show that naked mole-rat skin uncouples high cellular turnover from cancer risk through coordinated epithelial and stromal mechanisms that constrain clonal outgrowth and suppress tumor-promoting inflammation. Despite elevated epidermal proliferation and mutational burden, naked mole-rat skin maintains tissue integrity through an expanded pool of early committed progenitor (hybrid) cells and replication-coupled genome maintenance pathways. Under chronic carcinogenic stress, undifferentiated basal cells replenish the hybrid progenitor pool. This dilutes initiated clones and permits only limited selective expansion of rare cancer gene–mutant clones. Depletion of the hybrid compartment shifts this protective state toward clonal expansion and inflammatory activation. These expanding clones are further constrained by a highly tumor-suppressive stromal microenvironment, driven by fibroblasts that adopt a metabolically restricted, non-inflammatory program. Together, our data uncover a multi-layered tumor-suppressive strategy that couples turnover-driven regeneration with an anti-permissive stromal niche to prevent malignant progression under mutagenic stress.

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. Highlight Analyze of the ontogeny of the quiescent center during lateral root ontogeny reveal its late formation and supports that its emergence results from the establishment of two diverging growth axis.

Summary: Light sheet fluorescence microscopy (LSFM) is increasingly used to investigate biological processes in animals as well as in plants. LSFM achieves optical sectioning by the selective illumination of a single plane of the sample with a sheet of laser light while simultaneously recording emitted fluorescence orthogonally to the illumination plane. A 3D image of the sample can then be generated with a temporal resolution ranging from seconds to several days, and at scales ranging from subcellular to whole organ. By design, LSFM provides fast imaging, and low phototoxicity, two key criteria for live imaging under physiological conditions. Despite its potential, LSFM remains underutilized in plant biology. This review aims to highlight challenges of live imaging in plants, to describe key steps in using LSFM on live plant samples and finally at providing an overview of published examples of applications of LSFM in plants.