ABSTRACT
During secondary growth in most eudicots and gymnosperms, the periderm replaces the epidermis as the frontier tissue protecting the vasculature from biotic and abiotic stresses. Despite its importance, the mechanisms underlying periderm establishment and formation are largely unknown. The herbaceous Arabidopsis thaliana undergoes secondary growth, including periderm formation in the root and hypocotyl. Thus, we focused on these two organs to establish a framework to study periderm development in a model organism. We identified a set of characteristic developmental stages describing periderm growth from the first cell division in the pericycle to the shedding of the cortex and epidermis. We highlight that two independent mechanisms are involved in the loosening of the outer tissues as the endodermis undergoes programmed cell death, whereas the epidermis and the cortex are abscised. Moreover, the phellem of Arabidopsis, as in trees, is suberized, lignified and peels off. In addition, putative regulators from oak and potato are also expressed in the Arabidopsis periderm. Collectively, the periderm of Arabidopsis shares many characteristics/features of woody and tuberous periderms, rendering Arabidopsis thaliana an attractive model for cork biology.
